Industry Terms

What it means

A battery setup where the battery has its own inverter and connects to the solar system on the AC side. It is the easiest way to add storage to an existing solar site, but energy is converted more times, so a little more is lost.

In practice

A building owner adds a 250 kW / 500 kWh battery with its own inverter next to a rooftop array that has been running for four years.

Also known as: AC coupling

What it means

Using the same land for solar panels and farming, such as grazing sheep or growing crops under raised arrays. It can ease land-use concerns and help win local support, but design and O&M costs are usually higher.

In practice

A developer agrees to let a farmer graze sheep under a 5 MW array, which cuts mowing costs and helps the project through a county hearing.

Also known as: Dual-use solar

What it means

The share of sunlight a surface reflects. It matters most for bifacial modules, which collect reflected light on their back side.

In practice

Snow cover raises albedo and gives the bifacial array a winter boost.

Also known as: Ground reflectance

What it means

A detailed land survey that meets national standards and shows boundaries, easements, improvements and title issues. Lenders and title insurers rely on it.

In practice

The ALTA survey shows a drainage easement through the planned array, which the engineer designs around.

Also known as: ALTA/NSPS survey

What it means

Services that help keep the grid stable, such as frequency regulation and reserves. Batteries are well suited to provide them.

In practice

A battery earns most of its first-year revenue from ancillary services.

Also known as: Grid services

What it means

A thin layer on the module glass that cuts down reflection so more sunlight reaches the cells. It adds a small amount of output and also reduces glare.

In practice

A module datasheet lists an anti-reflective coated glass front, which helps the glare study near a small airport.

Also known as: ARC

What it means

Drawings updated after construction to show what was actually installed. O&M teams and owners rely on them for the life of the project.

In practice

The turnover package includes as-built drawings showing the final cable routes.

Also known as: As-builts

What it means

The work of looking after an operating project's technical, commercial and financial performance on behalf of its owner. The asset manager tracks output, contracts, billing, warranties, insurance and reporting so the project earns what the model promised.

In practice

An asset manager notices revenue is 6% below budget, traces it to a failed inverter, and files a warranty claim the same week.

Also known as: AM

What it means

Adding battery capacity over time to make up for degradation and keep the promised energy capacity.

In practice

The owner plans augmentation in years 5 and 10 to maintain 400 MWh.

Also known as: Battery augmentation

What it means

The agency or official responsible for approving permits and inspections, such as a building department or fire marshal.

In practice

The AHJ requires a rapid shutdown label at the main panel.

Also known as: AHJ

What it means

The share of time a plant is able to produce power when the sun or wind is available. O&M contracts often guarantee it.

In practice

Availability falls to 97% after two inverters are down for a week.

Also known as: Plant availability

What it means

The cost a utility saves by buying power from a project instead of making or buying it elsewhere. Under PURPA it sets the price for qualifying facilities.

In practice

A small project sells to the utility at its published avoided cost rate.

Also known as: PURPA rate

What it means

The compass direction that solar panels face. In the northern hemisphere, panels facing due south usually produce the most energy over a year.

In practice

A rooftop designer follows the building's 200 degree azimuth instead of rotating the racking, keeping the layout simple.

Also known as: Array azimuth

What it means

Everything in a solar system other than the modules, such as racking, inverters, wiring, combiner boxes, transformers and monitoring. BOS is often split into electrical (EBOS) and structural parts and is a large share of project cost.

In practice

An EPC's bid breaks out modules, inverters and BOS separately so the developer can see where the price moved.

Also known as: BOS, EBOS

What it means

Racking held in place by weight, like concrete blocks, instead of anchors. It is common on flat roofs and landfills.

In practice

A landfill project uses ballasted racking to avoid piercing the cap.

Also known as: Ballasted mount

What it means

The risk that the price at a project's location differs from the price at the hub used in its contract. It can erode revenue under virtual PPAs and hedges.

In practice

A VPPA settles at the hub, but the project's node trades lower, so the owner loses on basis.

What it means

A system that stores electricity in batteries and releases it later, including the battery racks, inverters, controls and safety equipment. It lets a project shift energy to higher-value hours, cut peak demand or provide grid services.

In practice

A 100 MW / 400 MWh BESS charges from midday solar and discharges during the evening peak.

Also known as: BESS, Battery storage

What it means

The electronics that monitor and protect battery cells, tracking voltage, temperature and state of charge.

In practice

The BMS takes a rack offline after detecting a cell over temperature.

Also known as: BMS

What it means

The tax rules for when a project counts as having started construction, which can lock in credit eligibility. For wind and solar under the 2025 law, the key deadline was July 4, 2026, and IRS Notice 2025-42 generally allows only the physical work test (starting significant on-site or off-site work); the 5% cost safe harbor survives only for solar of 1.5 MW AC or less. Projects must then keep construction moving continuously, with a four-year safe harbor.

In practice

The developer starts physical work on transformers to establish a begin construction date.

Also known as: Safe harbor

What it means

A project that serves a customer's own load on their side of the utility meter, cutting what they buy from the grid. Value comes from bill savings rather than wholesale sales.

In practice

A rooftop system on a distribution center is behind the meter and offsets about 40% of the site's annual use.

Also known as: BTM, On-site

What it means

A solar module that collects light on both its front and back. The extra output from the back depends on how reflective the ground is and how high the panels sit, so the gain varies by site.

In practice

A tracker project on light-colored gravel models a bifacial gain in PVsyst and asks the independent engineer to review the assumption.

Also known as: Bifacial module

What it means

Sending invoices to offtakers for energy, RECs or other services under the contracts.

In practice

The asset manager bills the PPA buyer monthly from revenue grade meter data.

Also known as: Invoicing

What it means

The ability of a power plant to restart without power from the grid, so it can help bring the grid back after a blackout. Some battery systems are designed and paid to provide this service.

In practice

A utility contracts a battery near a substation to help re-energize local lines after a wide outage.

Also known as: Black start

What it means

A tax rule that lets owners deduct eligible equipment cost in the first year instead of over time. The 2025 law restored a permanent 100% first-year deduction for qualifying property acquired after January 19, 2025. Property bought under a binding contract signed before that date may still be limited to the old, lower rate.

In practice

The model takes bonus depreciation in year one to boost tax benefits.

What it means

Solar materials that are built into the building itself, such as solar roof tiles, facades or glass, instead of panels mounted on top. It costs more per watt but can replace normal building materials.

In practice

An architect specifies BIPV glass on a south facade, so the solar cost is partly offset by the cladding it replaces.

Also known as: BIPV

What it means

Local approval to build a structure, confirming it meets building and fire codes. Rooftop and carport projects almost always need one.

In practice

The AHJ issues the building permit after reviewing structural calculations for the roof.

What it means

A small component in the module junction box that lets current go around a shaded or damaged group of cells. It limits power loss and helps prevent hot spots.

In practice

A chimney shades part of one module, and its bypass diodes keep the rest of the string producing.

What it means

Actual energy produced over a period divided by what the plant would make running at full nameplate power the whole time. It is a quick way to compare how hard different plants or sites work.

In practice

A 10 MWac solar farm that produced 21,900 MWh in a year had a capacity factor of 25%.

Also known as: CF, Net capacity factor

What it means

A market where grid operators pay resources to be available in future years. Payments depend on auction results and how much each resource is credited.

In practice

A battery clears the PJM capacity auction and earns a fixed payment per MW-day.

Also known as: Capacity auction

What it means

Revenue paid for being available to produce power, separate from payment for energy actually delivered.

In practice

The model shows capacity payments as a separate revenue line from energy sales.

What it means

A test that confirms the plant delivers the power the EPC guaranteed under measured conditions.

In practice

The plant passes its capacity test at 99.5% of expected output.

Also known as: Performance test

What it means

The upfront cost to build a project, including equipment, construction, interconnection and soft costs. CapEx is usually shown in dollars per watt and is one of the biggest inputs to project returns.

In practice

A developer's budget shows CapEx of $1.45 per watt DC before interconnection upgrades are added.

Also known as: CapEx, CAPEX

What it means

The mix of money that pays for a project, such as debt, tax equity and sponsor equity, and the order they get paid.

In practice

The capital stack is 40% tax equity, 45% debt and 15% sponsor equity.

Also known as: Cap stack

What it means

The total greenhouse gases caused by an activity, product or organization, usually counted in tons of CO2 equivalent. Buyers of clean power often use it to set and report climate goals.

In practice

A retailer signs a PPA partly to reduce the carbon footprint it reports to investors.

What it means

A large inverter, often several MW, that converts power from many strings at one location.

In practice

The utility-scale project uses four 4 MW central inverters on skids.

What it means

A formal change to an EPC contract's scope, price or schedule. Tracking them controls cost creep.

In practice

Unexpected rock leads to a change order adding $150,000 for pre-drilling.

Also known as: CO

What it means

A state rule that requires utilities to get a set share of electricity from clean sources, which can include nuclear or other non-renewable carbon-free power. It is similar to an RPS but usually broader in what counts.

In practice

A developer studies a state's CES targets to judge how much utility demand there will be for new projects.

Also known as: CES

What it means

A study approach where the grid operator reviews groups of projects together instead of one at a time, sharing upgrade costs among them.

In practice

Twenty projects in the same cluster share the cost of a new transmission line.

Also known as: Cluster process

What it means

An enclosure that joins several solar strings into one larger circuit before it goes to the inverter. It usually holds fuses and a disconnect for safety.

In practice

A crew lands 12 strings in each combiner box before running one larger feeder to the central inverter.

Also known as: Fused combiner

What it means

The date the project officially starts commercial operation, usually under its PPA. Many contracts and payments key off it.

In practice

COD is declared once PTO is granted and the PPA conditions are met.

Also known as: COD

What it means

Testing and verifying that every system works as designed before the project starts operating.

In practice

Commissioning includes IV curve tracing, inverter startup and SCADA checks.

Also known as: Cx

What it means

A list of tests and checks that must be completed and documented before a project can be turned over.

In practice

The commissioning checklist confirms every inverter passed startup tests.

What it means

A program that lets local governments buy power for residents and businesses instead of the utility doing it. CCAs often sign PPAs for renewables.

In practice

A CCA in California signs a 15-year PPA with a new solar plus storage project.

Also known as: CCA

What it means

A solar project whose power or bill credits are shared by many subscribers, such as households and small businesses, who could not install solar themselves. Rules, credit values and who can subscribe are set state by state.

In practice

A 5 MW community solar farm in New York signs 600 residential subscribers who each get a monthly bill credit.

Also known as: Shared solar, CSG

What it means

A local approval that allows a use, like a solar farm, that is permitted in a zoning district only if certain conditions are met. It usually involves public hearings.

In practice

The planning board grants a CUP with conditions for screening, setbacks and a decommissioning bond.

Also known as: CUP, Special use permit, SUP

What it means

When transmission lines are full, so cheaper power cannot reach where it is needed and prices differ by location.

In practice

Congestion cuts the price at the project's node during sunny afternoons.

Also known as: Transmission congestion

What it means

Short-term debt that funds building the project and is repaid at completion by tax equity or term debt.

In practice

The construction loan is drawn monthly against EPC milestones.

What it means

Repairs made after something breaks. Response times are set in the O&M contract.

In practice

A tech replaces a blown fuse within the 24-hour corrective maintenance window.

Also known as: Reactive maintenance, CM

What it means

Splitting project costs into tax categories, such as credit-eligible equipment versus land work, for credits and depreciation.

In practice

Cost segregation separates the fence and access road from credit-eligible equipment.

Also known as: Cost seg

What it means

How likely a buyer or partner is to pay what they owe over the life of a contract. Weak offtaker credit can make a project hard to finance or force extra security.

In practice

A lender asks for a parent guarantee because the PPA buyer is a small private company.

Also known as: Credit quality

What it means

The sequence of tasks that sets the earliest finish date. A delay on any of them delays the whole project.

In practice

Transformer delivery is on the critical path, so a two-week delay moves COD.

What it means

A study that checks a site for historic or archaeological resources that must be protected. It is often part of state or federal review.

In practice

The survey finds an old farmstead foundation, and the layout avoids it.

Also known as: Archaeological survey

What it means

When a project is told to reduce output, usually because of grid limits or very low prices. It lowers revenue unless the contract pays for it.

In practice

The plant is curtailed on spring afternoons when solar floods the grid.

What it means

The wind speed at which a turbine starts producing power.

In practice

With a 3 m/s cut-in speed, the turbines start spinning on light breezes.

What it means

The number of full charge and discharge cycles a battery can complete before its capacity falls to a set level, often 70% or 80% of new. It drives warranty terms and how often the battery can be used each day.

In practice

A battery warranty allows one full cycle per day for 15 years before augmentation is needed.

What it means

The monitoring system that collects data from meters, inverters and weather sensors for performance tracking.

In practice

The DAS flags a string inverter that stopped reporting overnight.

Also known as: DAS, Monitoring

What it means

The wholesale market where power is bought and sold for each hour of the next day. Most volume clears here.

In practice

The battery bids its evening discharge in the day-ahead market.

Also known as: DA market

What it means

The ratio of DC module capacity to AC inverter capacity. A higher ratio adds energy in low light but causes more clipping at midday.

In practice

A 7 MWdc array on 5 MWac of inverters has a DC/AC ratio of 1.4.

Also known as: ILR, Inverter loading ratio

What it means

A battery setup where the battery and solar share an inverter and connect on the DC side. It can capture energy that would be clipped and loses less in conversion, but it is harder to add to an existing site.

In practice

A new solar plus storage project sends clipped midday solar into a DC-coupled battery instead of losing it.

Also known as: DC coupling

What it means

A small device attached to each module that tunes its output before sending power to a string inverter. It reduces losses from shading or mismatch and gives module-level monitoring.

In practice

A rooftop with vents and HVAC units uses optimizers so shaded modules do not drag down the whole string.

Also known as: Power optimizer

What it means

Cash available for debt payments divided by the debt payments due. Lenders size loans so DSCR stays above a minimum.

In practice

The lender sizes debt at a 1.30x DSCR on P50 cash flows.

Also known as: DSCR

What it means

Working out how much a lender will loan based on cash flows, DSCR and other limits.

In practice

Debt sizing shows the project can support $12 million of term debt.

What it means

Cutting carbon emissions from the power sector, buildings, transport and industry. For developers it shows up as demand from utilities and companies with climate targets.

In practice

A university's decarbonization plan leads it to request proposals for on-site solar and a long-term PPA.

What it means

Removing a project at the end of its life and restoring the site. Many leases and permits require a plan and financial security for it.

In practice

The county requires a decommissioning bond before issuing the building permit.

Also known as: Decommissioning plan

What it means

How much a module's output declines each year as it ages, usually shown as a percentage. It is built into the financial model and backed by the manufacturer's warranty.

In practice

A model assumes 0.5% annual degradation, so year 10 output is about 95% of year one.

What it means

A part of a commercial electric bill based on the highest power the customer draws in a short window during the month, not on total energy used. Solar alone often does not cut it much, but batteries can.

In practice

A cold storage warehouse adds a battery to trim its monthly peak and lower its demand charges.

What it means

Programs that pay customers to reduce or shift their electricity use when the grid is stressed. Batteries and flexible loads are well suited to it.

In practice

A school district enrolls its battery in a utility demand response program and earns payments for summer events.

Also known as: DR

What it means

The timetable for deducting a project's cost from taxable income over several years. Solar projects have used accelerated schedules, which make tax benefits a key part of project returns.

In practice

A tax equity model uses 5-year MACRS on eligible costs to size the investor's tax benefits.

Also known as: MACRS

What it means

How much of a battery's capacity is used in a cycle. Deeper cycles usually wear the battery faster.

In practice

Limiting DoD to 90% helps the battery meet its warranty life.

Also known as: DoD

What it means

The payment a developer earns for creating a project, often paid at financial close or on sale.

In practice

The buyer pays a developer fee of $0.10 per watt at NTP.

Also known as: Dev fee

What it means

The checkpoints a project passes as it moves from idea to construction, such as site control, interconnection, permits and financing.

In practice

The developer reviews each project at development milestones before spending more money.

Also known as: Stage gates

What it means

The rate used to convert future cash flows to today's value, reflecting the time value of money and risk.

In practice

Raising the discount rate from 7% to 9% cuts the project NPV by a third.

What it means

Smaller power projects connected to the local distribution grid or at a customer's site, rather than large plants on the transmission system. Rooftop, carport and community solar are common examples.

In practice

A 2 MW ground mount connects to a 13.2 kV distribution line as a DG project.

Also known as: DG

What it means

An extra federal tax credit amount for projects that use enough US-made steel, iron and manufactured parts.

In practice

The procurement team tracks module and tracker origin to support a domestic content claim.

Also known as: Domestic content adder

What it means

The review of a project's contracts, permits, technical design and finances by lenders, investors or buyers before they commit.

In practice

Lender due diligence finds a missing easement, which delays close by a month.

Also known as: DD

What it means

How long a battery can discharge at full power, equal to energy capacity divided by power capacity.

In practice

A 50 MW / 200 MWh battery has a 4-hour duration.

Also known as: Storage duration

What it means

A right to use part of someone else's land for a specific purpose, such as access roads or power lines. Projects often need easements to reach the grid.

In practice

The project secures a 50-foot easement across a neighbor's field for its collection line.

Also known as: Right of way

What it means

The share of incoming sunlight a solar module or cell turns into electricity. Higher efficiency means more power from the same area, which matters most on tight roofs.

In practice

A roof with limited space uses 22% efficient modules to fit the customer's target system size.

Also known as: Module efficiency

What it means

A way for tax-exempt groups, such as cities, schools and co-ops, to receive certain clean energy credits as a cash payment.

In practice

A school district uses elective pay to receive the value of its rooftop solar credit.

Also known as: Direct pay

What it means

Local approval for electrical work that ensures it meets the electrical code. Inspections happen during and after installation.

In practice

The inspector signs off on the electrical permit after checking the AC disconnect and grounding.

What it means

Buying or storing energy when prices are low and selling or using it when prices are high. It is a main revenue stream for many batteries.

In practice

A Texas battery charges overnight at low prices and discharges into a high-priced evening hour.

What it means

An extra federal tax credit amount for projects in areas tied to fossil fuel jobs, brownfields or certain economic conditions.

In practice

An originator targets a former coal county because it may qualify for the energy community bonus.

Also known as: Energy community adder

What it means

The software that decides when a battery charges and discharges to meet revenue or customer goals.

In practice

The EMS discharges ahead of the monthly peak to cut demand charges.

Also known as: EMS

What it means

A modeled estimate of how much energy a project will produce each year, based on weather, design and losses. It drives revenue in the financial model.

In practice

The independent engineer reviews the energy yield assessment and trims the P50 by 1%.

Also known as: Production estimate, EYA

What it means

The licensed engineer who stamps the design drawings and takes professional responsibility for them.

In practice

The EOR stamps the structural drawings for the carport before the permit submission.

Also known as: EOR

What it means

A contract where one contractor designs, buys equipment for and builds the project for a set price and schedule.

In practice

The developer signs a fixed-price EPC contract with guaranteed completion dates.

Also known as: EPC, Engineering, procurement and construction

What it means

Measures like silt fence, seeding and basins that keep soil from washing off a construction site. They are required by permits and inspected often.

In practice

After grading, crews seed the site and add a sediment basin to meet the E&S plan.

Also known as: E&S, ESCP

What it means

A set annual increase in a contract price, such as a PPA rate or lease payment. Small changes in the escalator have a big effect on long-term value.

In practice

The PPA starts at $0.09 per kWh with a 2% escalator each year.

Also known as: Annual escalator

What it means

A signed statement from a counterparty confirming that a contract is in effect and no one is in default. Lenders and buyers ask for them at closing.

In practice

The landowner signs an estoppel confirming the lease is current before the project sale closes.

Also known as: Estoppel

What it means

A promise that the landowner or customer will not deal with other developers for a set time. It protects the developer's spending on early studies.

In practice

A 120-day exclusivity clause keeps the roof owner from signing with a competitor while the developer runs interconnection studies.

Also known as: Exclusivity period

What it means

A filing with the Federal Aviation Administration for structures that might affect air navigation, such as tall equipment or projects near airports. Wind turbines almost always need it.

In practice

The wind developer files FAA notices for every turbine location.

Also known as: Form 7460-1

What it means

The final utility study that designs the required interconnection facilities and gives firmer cost and schedule estimates.

In practice

The facilities study firms the upgrade cost, and the interconnection agreement follows.

What it means

The price a project would sell for between a willing buyer and a willing seller. Tax credits are usually based on cost, but when a project changes hands, the price paid (and its FMV) can set the new owner's credit basis. An independent appraisal helps defend that value if the IRS questions it.

In practice

An appraisal supports the FMV used to calculate the ITC.

Also known as: FMV

What it means

An early utility study that gives a first look at whether a project can connect and roughly what upgrades it may need.

In practice

The feasibility study suggests a new breaker at the substation may be needed.

What it means

A payment added on top of the market price for each unit of renewable energy produced. It is more common in Europe than in the US.

In practice

A European wind farm sells at market and earns a fixed premium per MWh under a FiP scheme.

Also known as: FiP

What it means

A long-term contract that pays a fixed price for each unit of renewable power a project delivers. It gives very predictable revenue and was used to start many early solar markets.

In practice

A small solar project signs a 20-year FiT with a municipal utility at a set price per kWh.

Also known as: FiT

What it means

Federal rules from 2025 that deny clean electricity credits to owners that are, or are controlled by, a 'prohibited foreign entity' (mainly tied to China, Russia, North Korea or Iran). Projects beginning construction after 2025 must also keep enough of their equipment cost from non-prohibited sources: at least 40% for generation and 55% for storage in 2026, rising each year. IRS Notice 2026-15 gives interim safe harbors, and more guidance is expected.

In practice

Procurement adds supply chain certifications to supplier contracts to address FEOC rules.

Also known as: Prohibited foreign entity (PFE), Foreign entity of concern

What it means

A 2023 federal rule that reformed interconnection on the transmission system, moving regions toward cluster studies and stricter readiness rules.

In practice

Grid operators rewrite their queue procedures to comply with FERC Order 2023.

Also known as: Order 2023

What it means

The milestone when all work, including punch list items and documents, is finished and retainage can be released.

In practice

Final completion is reached after the as-builts and warranties are delivered.

Also known as: FC

What it means

The point when all financing documents are signed and funds are available. It usually comes just before or at NTP.

In practice

Financial close happens two days before full NTP to the EPC.

What it means

Solar arrays mounted on floats on reservoirs, ponds or other water bodies. It saves land and can cut evaporation, but anchoring and electrical safety need special design.

In practice

A water utility installs floating solar on a treatment pond to power its pumps.

Also known as: FPV, Floatovoltaics

What it means

Fast adjustments to power output to keep grid frequency at its target. Grid operators pay for it.

In practice

The battery follows a regulation signal every few seconds.

Also known as: Regulation

What it means

A project that connects directly to the grid and sells power to a utility or market, not to a single on-site customer. Community and utility-scale solar are FTM.

In practice

A 5 MW ground mount sells all output to the utility as a front-of-the-meter project.

Also known as: FTM, In-front-of-the-meter

What it means

The power line that connects a project's substation to the utility's point of interconnection. The project usually builds and owns it.

In practice

A two-mile gen-tie connects the solar farm to the utility substation.

Also known as: Generation tie line

What it means

Testing of soil and rock to design foundations, piles and roads. Poor soils or shallow rock can raise construction costs.

In practice

The geotech report finds rock at 4 feet, so the racking switches to pre-drilled piles.

Also known as: Geotech

What it means

An analysis of whether reflected sunlight from panels could affect pilots, drivers or neighbors. Airports and the FAA may require it.

In practice

A project near a regional airport runs a glare study and adjusts tilt to avoid the approach path.

Also known as: Glint and glare study

What it means

The point where solar or other renewable power costs the same or less than power bought from the grid. Past that point, projects can make sense without subsidies.

In practice

A developer shows a customer that rooftop solar is at grid parity with their retail rate even before incentives.

What it means

The grid's ability to keep voltage and frequency steady as supply and demand change. Inverter-based resources help or hurt it depending on how they are controlled.

In practice

Smart inverter settings help a feeder with lots of solar keep voltage within limits.

What it means

A solar system connected to the utility grid, so it can export extra power and draw power when needed. Most commercial and utility projects are grid-tied.

In practice

A warehouse's grid-tied system exports surplus on weekends under net metering.

Also known as: Grid-connected

What it means

The area covered by modules divided by the total ground area of the array. Higher GCR fits more capacity but adds row-to-row shading.

In practice

Moving from 0.35 to 0.40 GCR adds capacity but increases shading losses in winter.

Also known as: GCR

What it means

Equipment that detects current leaking to ground and shuts down the circuit to prevent fires and shocks. Inverters include it and codes require it.

In practice

An inverter trips on a ground fault after rain, and the O&M tech finds a damaged cable at a combiner.

Also known as: GFP, GFDI

What it means

A long-term contract to rent land for a project, usually covering construction, operations and removal. Rent, term, renewals and decommissioning are key terms.

In practice

A 35-year ground lease pays the farmer $1,000 per acre per year with a 2% escalator.

Also known as: Land lease

What it means

Solar arrays installed on racking fixed to the ground rather than on a roof. They can be fixed tilt or tracking and range from small to utility scale.

In practice

A 3 MW community solar project uses fixed-tilt ground mount racking on a former hay field.

Also known as: Ground-mounted solar

What it means

The latest date by which a project must reach COD under its contract, or face penalties or termination.

In practice

Missing the guaranteed COD would let the buyer collect delay damages under the PPA.

Also known as: GCOD

What it means

A utility map showing roughly how much new generation each part of the distribution grid can take without upgrades. It is a fast screening tool.

In practice

An originator screens 30 parcels against the hosting capacity map and keeps the five on strong feeders.

Also known as: Hosting capacity

What it means

A small area of a module that overheats, often from shading, cell cracks or bad connections. It can cut output and cause damage.

In practice

The IR scan shows a hot spot on a module with a cracked cell, and it is replaced.

What it means

The height of the turbine's rotor center above the ground. Taller hubs reach stronger wind but face more permitting limits.

In practice

Raising hub height from 90 to 110 meters boosts the energy estimate.

What it means

A project that combines two or more resources, most often solar and batteries, behind one interconnection. It can deliver power more steadily and capture more value than either alone.

In practice

A 50 MW solar plus 25 MW battery hybrid shares one point of interconnection.

Also known as: Solar plus storage

What it means

The US standard for how distributed energy resources connect to and interact with the grid, including ride-through and smart inverter functions.

In practice

The utility requires inverters listed to UL 1741 SB for IEEE 1547-2018.

What it means

A third-party engineer hired by lenders or investors to review design, energy estimates, contracts and construction.

In practice

The IE signs off that substantial completion was achieved before the loan converts.

Also known as: IE

What it means

A company that owns power plants and sells electricity to utilities or other buyers, but is not itself a utility. Many renewable developers and owners are IPPs.

In practice

An IPP buys a late-stage solar project and signs a 20-year PPA with the local utility.

Also known as: IPP

What it means

Using thermal cameras, often on drones, to find hot modules, connections or equipment that may be failing.

In practice

A drone IR scan finds 15 modules with hot spots across the site.

Also known as: IR scan, Thermal imaging

What it means

The process and physical connection that lets a project deliver power to the grid. It includes applications, utility studies, upgrade costs and agreements, and it is often the biggest schedule risk in development.

In practice

A developer learns that interconnection will need a $900,000 line upgrade, which changes the project economics.

Also known as: IX

What it means

The contract between the project owner and the utility or grid operator that sets the terms for connecting and operating. It lists required upgrades, costs, milestones and technical rules.

In practice

After the facilities study, the developer signs an interconnection agreement and posts security for the upgrades.

Also known as: IA, GIA, ISA

What it means

The formal request to connect a project to the grid, with site control, design and a deposit. Filing it starts the study process.

In practice

The developer files the interconnection application with a $50,000 deposit and a preliminary SLD.

Also known as: IX application

What it means

The list of projects waiting for a utility or grid operator to study and approve their connection. Queues are long in many regions and drive development timelines.

In practice

The project enters the queue in March and expects study results in about 18 months.

Also known as: Queue

What it means

The fact that solar and wind output changes with weather and time of day. Grid operators manage it with forecasting, flexible plants and storage.

In practice

A cloud bank cuts a solar plant's output by half for 20 minutes, and a nearby battery fills the gap.

Also known as: Variability

What it means

The discount rate at which a project's NPV equals zero. Investors compare it to their target return.

In practice

The sponsor targets a 9% after-tax unlevered IRR.

Also known as: IRR

What it means

A nonprofit that works on clean energy rules, interconnection standards and workforce training. Its model rules shape many state interconnection policies.

In practice

A state commission uses IREC model interconnection procedures as a starting point for new rules.

Also known as: IREC

What it means

The device that changes DC power from solar panels or batteries into AC power the grid can use. It also handles grid protection, monitoring and controls.

In practice

A 5 MWac project uses 40 string inverters of 125 kW each.

What it means

Energy lost when the array produces more DC power than the inverter can convert, so output is capped. Some clipping is normal and planned.

In practice

On clear summer days the plant flatlines at 5 MW from noon to 2 pm due to clipping.

Also known as: Clipping loss

What it means

A federal tax credit equal to a percentage of a project's eligible cost, claimed when the project is placed in service (Section 48E for most projects starting after 2024). Under the 2025 law, wind and solar projects qualify only if construction began by July 4, 2026, or the project is placed in service by the end of 2027; storage is not subject to that cutoff. The credit's value depends on labor rules, bonus adders and foreign-sourcing limits, so confirm it for each project.

In practice

A developer models a base ITC and treats any adders as upside until counsel confirms eligibility.

Also known as: ITC, Section 48E, Section 48 (projects started before 2025)

What it means

When a system keeps powering local loads while disconnected from the grid. It needs special equipment and controls, and normal grid-tied inverters must shut off during outages.

In practice

During a storm outage, a hospital microgrid switches to island mode and runs on solar and batteries.

Also known as: Islanding

What it means

The final approved drawing set that crews build from. It follows the issued for permit set and earlier design stages.

In practice

The EPC cannot start installing racking until the IFC drawings are released.

Also known as: IFC drawings

What it means

A test that measures the current and voltage of a string to spot problems like damaged modules or wiring faults.

In practice

IV curve tracing during commissioning finds two strings with a broken connector.

Also known as: IV curve

What it means

The small sealed box on the back of a module where the cell wiring meets the output cables. It houses the bypass diodes.

In practice

An IR scan finds a hot junction box, and the module is swapped under warranty.

Also known as: J-box

What it means

A unit of power equal to 1,000 watts. It describes how much power a system can make or use at a moment, not total energy over time.

In practice

A small business has a 150 kW rooftop system.

Also known as: kW

What it means

A unit of energy equal to using or producing 1 kW for one hour. Utility bills and most energy sales are priced per kWh.

In practice

A 150 kW system that runs at full power for one hour produces 150 kWh.

Also known as: kWh

What it means

A short, usually non-binding document that sets out the main deal terms before a full contract is drafted. It often includes binding exclusivity and confidentiality.

In practice

A developer signs an LOI with a landowner covering rent, term and a 90-day exclusivity period.

Also known as: LOI

What it means

The average cost to produce each unit of energy over a project's life, including build, operating and financing costs. It is a common way to compare technologies and projects.

In practice

A developer compares the LCOE of fixed tilt versus tracker designs before choosing racking.

Also known as: LCOE

What it means

A laser-based tool that measures wind speeds at many heights from the ground, often used with or instead of met towers.

In practice

A LiDAR unit supplements the met tower to measure wind at hub height.

What it means

A partial go-ahead that lets the EPC start some work, such as engineering or ordering long-lead equipment, before full NTP.

In practice

An LNTP lets the EPC order the transformer while financing closes.

Also known as: LNTP

What it means

Preset payments a contractor owes if it misses deadlines or performance targets. They replace arguing over actual losses.

In practice

The EPC owes delay LDs for each day past the guaranteed substantial completion date.

Also known as: LDs

What it means

A battery chemistry widely used in stationary storage because of its safety, cost and cycle life.

In practice

The project selects LFP cells for lower fire risk and longer life.

Also known as: LFP

What it means

A record of how a customer's electricity use changes through the day and year. It drives system sizing and whether storage makes sense.

In practice

An originator uses 12 months of interval data to build the load profile before proposing a system size.

Also known as: Load curve

What it means

Moving electricity use from expensive hours to cheaper ones, often using batteries or flexible equipment. It lowers bills under time-of-use rates.

In practice

A factory charges a battery at night and runs off it during afternoon peak pricing.

What it means

The wholesale price of power at a specific grid location and time, including energy, congestion and losses.

In practice

The plant's node has a lower LMP than the hub because of local congestion.

Also known as: LMP, Nodal price

What it means

A safety procedure that locks and tags equipment de-energized so no one can turn it on while work is underway.

In practice

The tech applies LOTO at the inverter before opening the combiner.

Also known as: LOTO

What it means

Equipment with long delivery times, such as transformers, switchgear and trackers, that must be ordered early.

In practice

The transformer has a 60-week lead time, so it is ordered under LNTP.

Also known as: Long-lead items

What it means

The large transformer that raises project voltage to grid voltage. It often has very long lead times.

In practice

The developer orders the MPT 18 months before COD to protect the schedule.

Also known as: MPT, GSU

What it means

Money set aside to pay for big future repairs, like replacing inverters.

In practice

The lender requires a reserve funded each year for year 12 inverter replacement.

Also known as: MMRA, Inverter reserve

What it means

The combination of voltage and current at which a module or string makes the most power. It shifts with sunlight and temperature.

In practice

On a cold sunny morning, the array's MPP voltage rises, which the designer checks against inverter limits.

Also known as: MPP

What it means

Inverter electronics that keep adjusting to hold a string at its maximum power point. Inverters with more MPPTs handle mixed orientations and shading better.

In practice

A rooftop with east and west arrays puts each face on a separate MPPT input.

Also known as: MPPT

What it means

The milestone when equipment is installed and ready for testing but not yet fully commissioned.

In practice

Mechanical completion triggers the start of commissioning tests.

Also known as: MC

What it means

Voltage levels, roughly 1 kV to 35 kV, used for collection systems and distribution lines.

In practice

Inverter output is stepped up to 34.5 kV for the collection system.

Also known as: MV

What it means

A unit of power equal to 1,000 kilowatts. Utility and community scale projects are usually described in MW, either AC or DC.

In practice

The project is 5 MWac and 7 MWdc, so the DC/AC ratio is 1.4.

Also known as: MW

What it means

A unit of energy equal to 1,000 kWh. Wholesale prices and battery energy capacity are usually stated per MWh.

In practice

A 100 MW battery that runs for 4 hours stores 400 MWh.

Also known as: MWh

What it means

A short public record of a lease that is filed with the county so others know it exists, without revealing private terms. Lenders usually require it.

In practice

After signing, the developer records a memorandum of lease to protect its rights if the land is sold.

Also known as: MOL

What it means

A solar project that sells power into the wholesale market at whatever the price is, without a long-term contract. It has more upside and more risk, and lenders treat it cautiously.

In practice

A Texas project sells half its output merchant and hedges the rest with a contract.

Also known as: Merchant project

What it means

The years after a project's contract ends when it sells power at market prices. Lenders give it little credit.

In practice

The model assumes a 10-year merchant tail after the 25-year PPA.

Also known as: Post-PPA revenue

What it means

A tower with instruments that measures wind speed and direction at a site to support the energy estimate.

In practice

The developer collects two years of met tower data before financing.

Also known as: Meteorological tower, Met mast

What it means

A local energy system with its own generation and controls that can run connected to the grid or on its own. Campuses, military bases and critical facilities use them for resilience.

In practice

A fire station microgrid pairs rooftop solar, a battery and a generator to stay powered in outages.

What it means

A small inverter mounted under each module that converts power to AC right at the panel. It is common on homes and small roofs with shading or many orientations.

In practice

A church roof with dormers uses microinverters so each panel works independently.

Also known as: Micro

What it means

Payments to the EPC tied to completing defined steps, like delivery of equipment or mechanical completion.

In practice

The EPC gets 20% on module delivery and 30% at mechanical completion.

What it means

Washing modules to remove dirt and recover lost output.

In practice

The O&M provider cleans modules twice a year at the desert site.

Also known as: Panel washing

What it means

Lost energy when modules in a string do not perform the same, so the weakest one limits the others. It comes from shading, soiling, manufacturing spread or damage.

In practice

Mixing two module batches with different currents adds a small mismatch loss in the energy model.

Also known as: Mismatch loss

What it means

A monthly report to the owner on production, availability, issues, finances and actions.

In practice

The MOR explains that low production came from snow cover, not equipment failure.

Also known as: MOR

What it means

The housing on top of a wind turbine tower that holds the gearbox, generator and controls.

In practice

Technicians climb to the nacelle for the annual gearbox inspection.

What it means

A federal law requiring environmental review of projects that need federal permits, funding or land. Reviews range from simple exclusions to full environmental impact statements. In 2025 the White House CEQ withdrew its NEPA rules, so each agency now uses its own procedures, and the Supreme Court's Seven County decision told courts to defer to agencies on how broad a review must be.

In practice

A project on federal land must complete NEPA review before construction.

Also known as: National Environmental Policy Act

What it means

A compensation rule where a customer is paid for exported solar at a set rate, often lower than the retail price they pay. It makes self-use and batteries more valuable than under classic net metering.

In practice

Under a state net billing rule, exports earn far less than retail, so the customer adds a battery.

Also known as: Net billing tariff

What it means

A rule that lets one solar system's credits be applied across several meters owned by the same customer. It helps farms, schools and campuses with many accounts.

In practice

A farm uses NEM aggregation to apply credits from one barn array to five other meters.

Also known as: NEMA, Aggregate net metering

What it means

A billing rule that credits customers for solar power they send to the grid, usually at or near the retail rate. Many states have changed or reduced it.

In practice

A homeowner's meter spins backward at midday, and credits offset their winter bills.

Also known as: NEM

What it means

The value today of all a project's future cash flows, after discounting them for time and risk and subtracting the investment. A positive NPV means the project beats the required return.

In practice

At an 8% discount rate the project shows an NPV of $1.2 million, so it clears the investment committee.

Also known as: NPV

What it means

Changes to the shared grid, like new lines or substation equipment, needed to connect a project safely. Costs can make or break a project.

In practice

The utility assigns $800,000 in network upgrades to the project.

What it means

The fire code standard for installing stationary energy storage, covering spacing, size limits and safety systems.

In practice

The battery layout follows NFPA 855 spacing as adopted by the local fire code.

What it means

The standard voltage rating used to describe a system or battery, such as 12 V or 480 V. Actual voltage moves around this value during operation.

In practice

The inverter connects to the building's 480 V nominal service.

What it means

The formal instruction to the EPC to start full work. It usually follows financial close and permits.

In practice

Full NTP is issued on May 1 and the 9-month construction clock starts.

Also known as: NTP, FNTP

What it means

The contract that sets the O&M provider's scope, response times, pricing and guarantees.

In practice

The O&M agreement includes quarterly inspections and a 99% availability guarantee.

Also known as: O&M contract

What it means

A power system that is not connected to the utility grid and relies on its own generation and batteries. It is used in remote places where a grid connection is too expensive.

In practice

A remote telecom tower runs on an off-grid solar and battery system.

Also known as: Standalone system

What it means

Wind farms built in the ocean, where winds are stronger and steadier but costs and permitting are complex.

In practice

An offshore wind project secures a lease area and a state offtake contract.

What it means

The party that buys a project's power, RECs or capacity under a contract. Its credit quality is one of the first things lenders and investors check.

In practice

A county government is the offtaker for a 2 MW solar project under a 25-year PPA.

Also known as: Buyer

What it means

The voltage a module makes in sunlight when nothing is connected. Designers use it, adjusted for cold weather, to make sure strings never exceed equipment voltage limits.

In practice

The designer limits strings to 26 modules so cold-morning Voc stays under 1,500 V.

Also known as: Voc

What it means

The ongoing costs of running a project, such as O&M, insurance, land lease, property tax and asset management. It reduces cash flow every year of operation.

In practice

A model assumes OpEx of $18 per kW per year with a 2% annual escalator.

Also known as: OpEx, OPEX

What it means

The day-to-day work that keeps a project running, including inspections, repairs, cleaning, vegetation control and monitoring. It is usually done by a contractor under an O&M agreement.

In practice

The O&M provider replaces a failed inverter fan within the 48-hour response time in its contract.

Also known as: Operations & Maintenance, O&M

What it means

A contract that gives the developer the right, but not the duty, to lease or buy land later, for a small payment now. It locks up the site while diligence and interconnection move forward.

In practice

A developer pays $5,000 a year for a three-year option before deciding whether to sign the full lease.

Also known as: Option to lease

What it means

Production estimates with a 50% or 90% chance of being exceeded in a year. Equity often uses P50; lenders size debt on P90 or P99.

In practice

Debt is sized on a P99 one-year case while equity returns use P50.

Also known as: P50, P90, P99

What it means

A tax equity structure where the investor gets most tax benefits until it hits a target return, then its share drops and the sponsor gets more.

In practice

The investor gets 99% of tax benefits until its target return, then flips to 5%.

Also known as: Flip

What it means

How long it takes for savings or income to repay the upfront cost. It is easy to explain to customers but ignores value after payback and the time value of money.

In practice

A rooftop system for a car dealer has a 6 year simple payback.

Also known as: Simple payback

What it means

The highest level of electricity use in a period, for a customer or the whole grid. It drives demand charges, capacity costs and grid planning.

In practice

A summer heat wave pushes the utility's peak demand to a new record at 6 pm.

Also known as: Peak load

What it means

Using a battery or other resource to cut a customer's highest demand and lower demand charges.

In practice

The battery shaves 300 kW off the factory's monthly peak.

What it means

The number of hours per day the sun would deliver 1,000 W per square meter if spread evenly. It is a quick way to estimate production at a site.

In practice

A site with 4.5 peak sun hours makes roughly 4.5 kWh per kW of panels on an average day before losses.

Also known as: PSH

What it means

A promise that a project will produce a set amount of energy or reach a set performance level, with payments if it falls short. EPCs, O&M providers and PPA sellers may give them.

In practice

The O&M contract guarantees 99% availability and pays the owner for lost revenue below that.

Also known as: Production guarantee

What it means

Actual energy produced divided by the energy expected from the sunlight that hit the array. It shows how well the system is working regardless of weather.

In practice

A month with low output but a normal PR tells the asset manager the cause was weather, not equipment.

Also known as: PR

What it means

The utility's written approval to start running the project and exporting power.

In practice

The project gets PTO two weeks after the witness test and begins earning revenue.

Also known as: PTO

What it means

A list of every permit a project needs, with the agency, timeline, cost and status. It keeps permitting on schedule.

In practice

The permitting matrix shows the stormwater permit is on the critical path for NTP.

Also known as: Permit matrix

What it means

A newer type of solar cell made from crystal materials that are cheap to make and can be very efficient. Long-term durability is still being proven, so it is mostly in research and pilot products.

In practice

A module maker tests perovskite on silicon tandem cells in a pilot line.

What it means

A desk and site review that looks for past contamination or environmental problems on a property. Lenders usually require it before closing.

In practice

The Phase I ESA flags an old fuel tank, so the developer orders a Phase II.

Also known as: Phase I Environmental Site Assessment

What it means

Sampling of soil or groundwater to confirm whether contamination found in a Phase I is real and how bad it is.

In practice

Soil samples near the old tank come back clean, clearing the site for construction.

Also known as: Phase II Environmental Site Assessment

What it means

The technology that turns sunlight directly into electricity using semiconductor cells. Solar panels are PV modules.

In practice

The project uses PV modules on single-axis trackers.

Also known as: PV

What it means

An agreement to pay a set amount to a local government instead of normal property taxes.

In practice

The county agrees to a 20-year PILOT at a fixed amount per MW.

Also known as: Payment in lieu of taxes

What it means

The date a project is ready and available to operate for tax purposes. It sets when credits and depreciation begin.

In practice

Tax counsel confirms the placed in service date matches the commissioning records.

Also known as: PIS

What it means

The exact location where a project connects to the utility grid. It sets where metering and ownership change hands.

In practice

The POI is a new breaker position at the utility's 69 kV substation.

Also known as: POI

What it means

Power loss caused by voltage differences between cells and the module frame, often worse in heat and humidity.

In practice

Output drops at the end of strings, and testing confirms PID.

Also known as: PID

What it means

The inverter equipment that converts battery DC power to AC and back again.

In practice

The PCS is sized at 50 MW to match the interconnection limit.

Also known as: PCS

What it means

A chart showing how much power a wind turbine makes at each wind speed. It is used to estimate production and test turbine performance.

In practice

An owner tests a turbine against its warranted power curve after output drops.

What it means

The ratio of real power to total power in an AC system. Grid rules often set a required range for projects.

In practice

The utility sets a fixed power factor setting that slightly reduces real power export.

Also known as: PF

What it means

A long-term contract where a buyer agrees to purchase power from a project at a set price. It is the main revenue contract that makes many projects financeable.

In practice

A school district signs a 20-year PPA at a fixed rate with a 2% escalator.

Also known as: PPA

What it means

A low-cost request to the utility for basic information about the grid near a site before filing a full application.

In practice

The pre-application report shows the feeder is near its limit, so the developer moves to another site.

Also known as: Pre-app

What it means

Labor rules that projects must meet to earn the full federal credit amount, covering wage rates and use of registered apprentices.

In practice

The EPC submits weekly payroll records to show prevailing wage compliance.

Also known as: PWA

What it means

Scheduled maintenance done to prevent failures, such as inspections, torque checks and filter changes.

In practice

The PM plan includes annual IR scans and inverter servicing.

Also known as: PM

What it means

A financial model projecting a project's revenue, costs and returns over its life.

In practice

The pro forma shows a 1.5% higher IRR with trackers instead of fixed tilt.

Also known as: Financial model

What it means

Buying major equipment and services for a project, including vendor selection, contracts, logistics and quality checks.

In practice

Procurement locks module pricing six months before delivery.

What it means

A federal tax credit paid for each unit of electricity a project produces during its first ten years of operation (Section 45Y for most projects starting after 2024). Wind and solar projects qualify only if construction began by July 4, 2026, or the project is placed in service by the end of 2027. It can beat the ITC at high-output sites, but labor rules and foreign-sourcing limits also affect its value.

In practice

A high-output wind farm elects the PTC because it produces more value than the ITC.

Also known as: PTC, Section 45, 45Y

What it means

Local tax on the project's land and equipment, often one of the biggest operating costs.

In practice

Property tax is the second-largest operating cost after O&M in the model.

What it means

A field test that pulls on driven piles to confirm they can hold the design loads. Results set pile depth and type.

In practice

Pull tests at 20 locations show piles need to go 2 feet deeper than planned.

Also known as: Pile load test

What it means

A list of small items still to fix or finish near the end of construction.

In practice

The punch list includes missing labels and a damaged fence post.

What it means

Widely used software for modeling solar energy production and losses. Banks and independent engineers expect a PVsyst report for most projects.

In practice

The bank's IE requests the PVsyst report and loss diagram with the financing package.

What it means

The checks that confirm work meets design and quality standards during construction.

In practice

QA/QC inspections catch loose module clamps before final torque checks.

Also known as: Quality assurance and quality control

What it means

A small renewable or efficient power plant (up to 80 MW for renewables) that qualifies under the federal PURPA law. QFs can often require the local utility to buy their power at its avoided cost. In organized markets, however, utilities may be excused from buying from QFs larger than 5 MW.

In practice

An 80 MW solar project qualifies as a QF and gets a contract at avoided cost.

Also known as: QF, PURPA

What it means

A project's place in the interconnection queue, which affects study order and who pays for upgrades.

In practice

A developer buys a project mainly for its early queue position.

What it means

The metal structure that holds solar modules on a roof or the ground at the right angle. It must handle wind, snow and the site's soil or roof conditions.

In practice

A flat-roof project uses ballasted racking to avoid roof penetrations.

Also known as: Racking, Mounting system

What it means

Power that supports grid voltage but does no useful work. Utilities often require projects to supply or absorb it.

In practice

The interconnection agreement requires the plant to operate between 0.95 leading and lagging power factor.

Also known as: VAR

What it means

The wholesale market that balances supply and demand within the operating day, often in 5-minute intervals. Prices can swing widely.

In practice

A sudden plant outage spikes real-time prices and the battery discharges.

Also known as: RT market

What it means

In regulated markets a single utility owns generation and sells power at approved rates. In deregulated markets generation competes and customers may choose suppliers.

In practice

Ohio's retail choice lets a business shop for power, while Georgia's utility sets regulated rates.

Also known as: Vertically integrated, Retail choice

What it means

A tradable certificate that represents the environmental benefits of 1 MWh of renewable power. RECs can be sold separately from the electricity and are often a meaningful revenue stream.

In practice

A project sells its RECs to a utility to meet that utility's RPS obligation.

Also known as: REC, SREC

What it means

A goal set by a government or company for how much energy will come from renewables by a certain date. Unlike an RPS, it may not be legally binding.

In practice

A city sets a renewable energy target and asks for proposals for local solar.

Also known as: RET

What it means

A credit used in the US Renewable Fuel Standard to track biofuel production and use. It is a fuels market tool and rarely touches solar or storage projects.

In practice

A biogas facility earns RINs for fuel it supplies to vehicle fleets.

Also known as: RIN

What it means

A state law requiring utilities to get a set percentage of their power from renewables by a target date. It creates demand for RECs and new projects.

In practice

A state RPS raises its solar carve-out, which lifts SREC prices.

Also known as: RPS

What it means

Replacing old turbines or equipment with newer technology at an existing site to boost output and extend life.

In practice

A 2005 wind farm is repowered with larger turbines on the same pads.

What it means

A formal question from the contractor to clarify drawings or specs. Slow answers can delay work.

In practice

The EPC issues an RFI on a conflict between the civil and electrical drawings.

Also known as: RFI

What it means

Having enough generation available to meet peak demand with a safety margin. Projects can earn payments for providing it.

In practice

A 4-hour battery signs an RA contract with a California utility.

Also known as: RA, Capacity

What it means

A share of each payment, often 5% to 10%, held back until the project is complete.

In practice

The owner holds 5% retainage until final completion and punch list closeout.

Also known as: Retention

What it means

The approval from a manufacturer to send back a failed part for repair or replacement.

In practice

The inverter maker issues an RMA and ships a replacement board.

Also known as: RMA

What it means

The total gain from an investment compared with its cost, shown as a percentage. It is simple but ignores timing, so investors also use IRR and NPV.

In practice

A customer's rooftop system shows a lifetime ROI of 180%.

Also known as: ROI

What it means

A high-accuracy meter that measures energy for billing and incentive payments.

In practice

REC production is reported from the revenue grade meter, not inverter data.

Also known as: RGM

What it means

Checking that payments received match energy delivered and contract terms.

In practice

Reconciliation finds the buyer used the wrong escalator for three months.

What it means

A strip of land used for roads, pipelines or power lines, either owned or held by easement. Crossing public or utility rights of way needs permits.

In practice

The gen-tie needs a permit to cross the county road right of way.

Also known as: ROW

What it means

A review of a roof's age, condition, structure and electrical setup to see if it can host solar.

In practice

The roof assessment shows only 5 years of warranty left, so the owner replaces the roof first.

Also known as: Roof survey

What it means

A contract to rent roof space for a solar system, including access, roof repairs and what happens if the roof must be replaced. It must line up with the building's own leases and mortgage.

In practice

A rooftop lease requires the owner to give 60 days notice before any roof work so panels can be removed safely.

Also known as: Roof lease

What it means

The width of the circle swept by the blades. Bigger rotors capture more energy, especially at low wind speeds.

In practice

The newer turbine model has a larger rotor diameter for the low-wind site.

What it means

The share of energy put into a battery that comes back out. The rest is lost as heat and to equipment.

In practice

With 85% RTE, a battery charged with 100 MWh delivers about 85 MWh.

Also known as: RTE

What it means

Independent organizations that run the wholesale power market and transmission grid in a region, such as PJM, ERCOT, CAISO and MISO.

In practice

The project sells into PJM, which runs the regional market and the interconnection queue.

Also known as: RTO, ISO

What it means

A structure where the developer sells the project to an investor and leases it back to operate it. The investor takes the tax benefits.

In practice

The developer closes a sale-leaseback at COD and pays rent to the investor for 20 years.

Also known as: SLB

What it means

The system that monitors and controls plant equipment remotely and lets the utility send commands.

In practice

The utility uses SCADA to curtail the plant during a grid event.

Also known as: Supervisory control and data acquisition

What it means

The document listing exactly what a contractor will and will not do. Gaps cause change orders.

In practice

The SOW makes the EPC responsible for utility coordination up to the POI.

Also known as: SOW

What it means

Shorthand for the federal investment credit (Section 48, now Section 48E) and production credit (Section 45, now Section 45Y) for clean power; the older sections cover projects that began construction before 2025. Owners choose one or the other for each project. Wind and solar face a 2025-law cutoff: construction must have begun by July 4, 2026, or the project must be placed in service by the end of 2027.

In practice

A developer runs both credit cases in the model before choosing ITC or PTC.

Also known as: 48E, 45Y, ITC, PTC

What it means

The minimum distance a project must stay from property lines, roads, homes or other features under local rules. Setbacks can shrink the usable area a lot.

In practice

A 100-foot setback from neighboring homes cuts the array size from 6 MW to 5 MW.

What it means

A study of how trees, buildings, terrain or other rows will shade the array during the year and how much energy that costs.

In practice

A shading analysis shows a tree line costs 4% of output, so the developer negotiates clearing rights.

What it means

The flickering shadow from moving turbine blades on nearby homes. Local rules may limit hours of exposure.

In practice

The model shows shadow flicker at two homes, so turbines are curtailed at sunrise.

What it means

The current a module makes in sunlight when its terminals are shorted. Designers use it to size wires, fuses and inverter inputs.

In practice

The engineer sizes combiner fuses using module Isc times the code safety factor.

Also known as: Isc

What it means

The state office that reviews how projects might affect historic and cultural sites. Its sign-off may be needed for permits or federal approvals.

In practice

The developer submits the cultural survey to SHPO and gets a no-effect letter.

Also known as: State Historic Preservation Office

What it means

A simplified drawing of a project's electrical system showing major equipment and how it connects. Utilities, permit offices and engineers all use it.

In practice

The utility asks for an updated single-line diagram showing the new recloser.

Also known as: SLD, One-line

What it means

The legal right to build and operate a project on a piece of land or roof, through a lease, option, easement or ownership. Utilities and investors want proof of it early.

In practice

The interconnection application asks for evidence of site control, so the developer submits a signed option.

What it means

Practices that keep workers and visitors safe during construction and operation.

In practice

Site safety rules require arc flash PPE for anyone opening the switchgear.

What it means

An inverter that can actively support the grid, for example by adjusting voltage, riding through disturbances or following utility commands. Many utilities now require these functions.

In practice

The utility requires smart inverter volt-var settings as a condition of interconnection.

Also known as: Advanced inverter

What it means

An agreement with the landowner's lender that the project can stay in place even if the lender forecloses on the property. Financiers usually require it for leased sites.

In practice

Before financing, the developer gets an SNDA from the bank that holds the warehouse mortgage.

Also known as: Subordination, Non-Disturbance and Attornment Agreement

What it means

Lost energy from dust, pollen, bird droppings or snow on modules. Cleaning is scheduled when the gain beats the cost.

In practice

A dry summer shows 4% soiling loss, so the owner orders a module wash.

Also known as: Soiling

What it means

The basic unit of a solar module that turns light into electricity. Cells are wired together and sealed behind glass to make a module.

In practice

A 144 half-cut cell module has its cells arranged in two halves to reduce losses.

Also known as: PV cell

What it means

Energy from sunlight, used to make electricity with PV or to make heat. It is the fastest-growing source of new power in many markets.

In practice

A utility's resource plan adds more solar energy than any other source.

What it means

A large ground-mounted solar installation that sells power to the grid or a buyer. The term usually means community or utility scale projects.

In practice

A 20 MW solar farm sells its output to a cooperative utility.

Also known as: Solar park

What it means

The total solar energy that reaches a surface over time, usually in kWh per square meter per day or year. It is a key input for production estimates.

In practice

Annual insolation data from a weather file feeds the PVsyst model.

Also known as: Insolation

What it means

The power of sunlight hitting a surface at a moment, measured in watts per square meter. Plants measure it on site to judge performance.

In practice

A pyranometer reading of 950 W/m2 helps confirm the plant is producing as expected.

Also known as: GHI, POA

What it means

An arrangement where a customer pays a fixed monthly fee to use a solar system owned by someone else. The owner keeps tax benefits and handles maintenance.

In practice

A homeowner pays a fixed lease payment for 20 years and the leasing company maintains the system.

What it means

The share of a customer's annual electricity use that a solar system is expected to cover. It guides system sizing and net metering limits.

In practice

A proposal sizes the system for a 70% offset to stay within the utility's net metering cap.

Also known as: Offset

What it means

A framed, sealed group of solar cells that makes DC power. Modules are rated in watts and are the main equipment purchase in a project.

In practice

The project buys 9,000 modules rated at 580 W each.

Also known as: Module, Panel

What it means

The range of light wavelengths from the sun, from ultraviolet to infrared. Different cell types capture different parts of it.

In practice

Researchers stack two cell types to capture more of the solar spectrum.

What it means

The energy a system produces per unit of installed capacity, often kWh per kWp per year. It lets you compare sites of different sizes.

In practice

A site with a specific yield of 1,400 kWh/kWp outperforms another at 1,200.

Also known as: Specific yield

What it means

A table showing where a project's money comes from and what it pays for. Both sides must balance.

In practice

Sources and uses shows tax equity, debt and sponsor equity covering EPC, interconnection and fees.

Also known as: S&U

What it means

Replacement equipment kept on hand to cut downtime, such as modules, fuses and inverter boards.

In practice

Keeping a spare inverter on site saves two weeks of downtime.

Also known as: Spares inventory

What it means

The cash the project owner invests, which is paid last and takes the most risk.

In practice

The sponsor contributes 15% of project cost and holds the long-term upside.

Also known as: Developer equity

What it means

How full a battery is, shown as a percentage of its usable capacity. Operators manage it to meet commitments and protect battery life.

In practice

The battery holds 90% SOC before the evening peak to be ready for a capacity call.

Also known as: SOC

What it means

A permit that covers stormwater runoff from construction, usually under the federal NPDES program run by the state.

In practice

The project files a notice of intent for stormwater coverage before clearing begins.

Also known as: NPDES construction permit

What it means

How modules are wired in series into strings and how strings connect to inverters. It must keep voltage and current within equipment limits in all weather.

In practice

The engineer sets 28 modules per string and 18 strings per inverter.

Also known as: Stringing

What it means

A mid-size inverter that takes power from several strings of modules. It is the most common choice for commercial and many utility projects.

In practice

A 3 MWac carport project uses 24 string inverters mounted on the canopy columns.

What it means

An engineering check that a roof, carport or ground structure can carry the weight and wind loads of the solar system.

In practice

The structural analysis shows the roof needs reinforcing in two bays.

Also known as: Structural review

What it means

A customer who signs up for a share of a community solar project and receives bill credits. Subscriber management is an ongoing cost.

In practice

The subscription manager replaces 40 subscribers who moved out of the area.

Also known as: Community solar subscriber

What it means

The milestone when the project is complete enough to operate as intended, with only minor items left. It often ends delay LDs.

In practice

The IE confirms substantial completion once the capacity test passes.

Also known as: SC

What it means

A facility with transformers and switching equipment that steps up voltage and connects the project to the grid.

In practice

The project substation steps 34.5 kV up to 138 kV.

Also known as: Project substation

What it means

A plan that shows how a construction site will control erosion and keep sediment out of waterways. Sites that disturb an acre or more generally need one.

In practice

The EPC posts the SWPPP on site and inspects silt fences after every major rain.

Also known as: Stormwater Pollution Prevention Plan

What it means

A detailed utility study of how a project would affect the grid, identifying needed upgrades and their rough costs.

In practice

The SIS identifies $1.2 million of network upgrades, so the developer reconsiders the project size.

Also known as: SIS

What it means

Investment from a company that can use a project's tax credits and depreciation, in exchange for a share of cash and tax benefits. It is a core part of many capital stacks.

In practice

A bank invests tax equity for most of the project's tax benefits and a small cash share.

Also known as: TE

What it means

How much a module's power or voltage changes for each degree of temperature change. Lower power coefficients mean less loss in hot weather.

In practice

A desert project picks modules with a better temperature coefficient to reduce summer losses.

What it means

Long-term debt repaid from project cash flows over many years. It may sit at the project or holding company level.

In practice

A 18-year term loan replaces the construction loan at COD.

Also known as: Back leverage

What it means

A summary of the key commercial terms of a financing, sale or contract that the parties use to negotiate the final documents. Most terms are non-binding.

In practice

A tax equity investor sends a term sheet with its pricing, flip date and conditions to close.

What it means

A chain reaction where a battery cell overheats and spreads heat to nearby cells, which can lead to fire.

In practice

Spacing and fire testing are used to show thermal runaway will not spread between enclosures.

What it means

When a company other than the site owner owns the solar system and sells its power or leases it to the customer. It lets customers go solar with no upfront cost.

In practice

A nonprofit hospital uses TPO through a PPA so the owner can use the tax credits.

Also known as: TPO

What it means

A label for module makers judged bankable by a widely used industry ranking. It speaks to financial strength, not product quality.

In practice

The lender requires Tier 1 modules in the EPC contract.

Also known as: Tier 1

What it means

The angle of the modules from horizontal. Designers balance energy, row spacing, wind load and snow shedding when picking it.

In practice

A flat roof uses a 10 degree tilt to fit more rows and reduce wind loads.

Also known as: Tilt

What it means

A utility rate where the price of electricity changes by time of day and season. It rewards using or storing energy for high-price hours.

In practice

Under a TOU rate, a battery charged from midday solar saves more by discharging from 4 to 9 pm.

Also known as: TOU

What it means

A report from a title company showing who owns the land and what liens, easements or restrictions affect it. It is reviewed alongside the survey before financing.

In practice

The title commitment reveals an old pipeline easement, so the layout is shifted.

Also known as: Title report

What it means

Racking that rotates modules to follow the sun during the day, adding energy compared with fixed tilt. Single-axis trackers are standard on many utility projects.

In practice

A Texas project picks single-axis trackers for about 15 to 20% more energy than fixed tilt in the model.

Also known as: Single-axis tracker, SAT

What it means

The option to sell federal clean energy tax credits to an unrelated buyer for cash. It simplifies financing for owners without tax appetite.

In practice

The sponsor sells its ITC to a corporate buyer at a discount to face value.

Also known as: Tax credit transfer

What it means

The documents the EPC hands to the owner at the end of construction, such as as-builts, manuals, warranties and test reports.

In practice

The O&M team uses the turnover package to set up its maintenance plan.

Also known as: Handover package

What it means

A weather data set that represents typical conditions at a site, built from many years of history. It is the standard input for energy models.

In practice

The designer loads a TMY file from a nearby station into PVsyst.

Also known as: TMY

What it means

Safety standards for PV modules covering electrical and fire safety. UL 61730 has replaced UL 1703 for new listings, so check which applies to your equipment.

In practice

The AHJ asks for proof that the modules are listed to UL 61730.

Also known as: UL 61730

What it means

Safety standards for energy storage systems. UL 9540 certifies the system, and UL 9540A tests how fire spreads.

In practice

The fire marshal asks for UL 9540A test results before approving the battery layout.

Also known as: UL 9540A

What it means

Large solar projects, often 20 MW and up, that sell power to utilities or the wholesale market and connect to transmission or high voltage lines.

In practice

A 200 MW utility-scale project connects to a 230 kV substation.

Also known as: Utility solar

What it means

The approved price list and rules a utility uses to bill customers or pay generators. Tariffs set the savings or revenue a project can earn.

In practice

An originator reviews the customer's commercial tariff to see how much of the bill is demand charges.

Also known as: Rate schedule

What it means

Controlling grass and weeds at a site so they do not shade panels, create fire risk or block access.

In practice

The site switches from mowing to sheep grazing to cut vegetation costs.

Also known as: Mowing

What it means

Many small energy resources, such as home batteries and smart thermostats, controlled together to act like one power plant. It can supply capacity or grid services.

In practice

A utility pays 5,000 homeowners to let it dispatch their batteries as a VPP during heat waves.

Also known as: VPP

What it means

A financial contract where a buyer and project settle the difference between a fixed price and the market price, without the buyer taking physical power. Corporations use it to claim RECs from distant projects.

In practice

A tech company signs a VPPA with a Texas solar farm and receives the RECs while settling against the hub price.

Also known as: VPPA, Financial PPA, Contract for differences

What it means

Energy lost when turbines downwind sit in the slower, turbulent air left by upwind turbines.

In practice

The layout spaces turbines farther apart to reduce wake losses.

Also known as: Wake effect

What it means

A request to an equipment maker to repair or replace failed equipment under its warranty.

In practice

The asset manager files a warranty claim for 30 modules with cracked glass.

What it means

The watt is the basic unit of power, and a kilowatt is 1,000 watts. Module ratings are in watts and system sizes are in kW or MW.

In practice

A 400 W module is 0.4 kW, so 250 of them make a 100 kW system.

Also known as: W, kW

What it means

Comparing actual output to what the plant should have made given the real weather, to separate equipment problems from weather.

In practice

Weather-adjusted performance shows the plant at 98% of expected despite low production.

Also known as: Expected vs actual

What it means

The blended cost of all the money funding a project, weighted by each source's share. It is often used as the discount rate.

In practice

The model uses a 7.5% WACC to value the portfolio.

Also known as: WACC

What it means

A field study that maps where wetlands are on a site so the project can avoid them or get permits. Wetland impacts can add months of permitting.

In practice

The wetland delineation shrinks the buildable area by 8 acres.

What it means

A permit needed to fill or disturb wetlands or waters, often from the Army Corps of Engineers under the Clean Water Act.

In practice

A road crossing a small stream needs a wetland permit.

Also known as: Section 404 permit

What it means

A machine that turns wind into electricity using a rotor, gearbox or direct drive generator and a tower.

In practice

The project installs 30 turbines rated at 4.5 MW each.

Also known as: WTG

What it means

A test of the project's protection and controls observed by the utility before it allows full operation.

In practice

The utility witnesses the trip test on the recloser before granting PTO.

What it means

Local rules that set what can be built where. Projects may be allowed by right, need a special permit, or be banned in a zoning district.

In practice

The parcel is zoned agricultural, so the developer applies for a conditional use permit.

Also known as: Land use approval