“Best Practices for Operation and Maintenance of Photovoltaic and Energy Storage Systems, 3rd Edition” is the standing reference for PV and storage O&M, published through the National Renewable Energy Laboratory and available free from OSTI.
Its stated purpose is to reduce the cost and improve the effectiveness of O&M while making those costs more predictable. Scope covers maintenance planning, technical improvements in system design, equipment specifications, quality management standards, and strategies for improving financing predictability by mitigating performance risk.
How it gets used on a real project
This is the document to reach for when writing or reviewing an O&M scope of work. Most disputes between owners and service providers come from a scope that never specified frequency, method or acceptance criteria clearly enough, and this guide is where those definitions already exist in language both sides will accept.
The financing angle is the part people underrate. O&M assumptions feed directly into the operating expense line that sizes debt, and a documented practice backed by a recognised guide is materially easier to defend in diligence than a number someone carried forward from the last deal.