For leases and PPAs

Production guarantee check: are you owed money?

Most solar leases and PPAs promise the system will make a minimum amount of power, and pay you back if it doesn't. Enter the numbers from your contract and your monitoring app to see whether you're owed a refund, and get a letter to claim it.

How production guarantees work

• The promise. The contract lists the power the system is expected to make each year. The guarantee covers a share of it: Sunrun's recent disclosures, for example, promise 90% of the estimate, and some of its PPAs promise 100%. If the system falls short, the company pays you for the difference.
• The period. Shortfalls are usually measured over a set period, often one or two years, not month by month. A bad month can be made up later in the same period, so check the dates in your contract.
• The rate. Some contracts list a refund rate per kWh. SunPower's, for example, divides your payments over the period by the estimated production for that period; for a prepaid lease, the prepayment divided by the production expected over the whole term.
• Is it automatic? Some companies monitor every system and credit shortfalls on their own; others wait for you to ask. If a period has ended and you've heard nothing, ask in writing.

What can cancel a guarantee

• Monitoring offline. SunPower's guarantee, for example, depends on its monitoring staying connected: being offline for more than a month affects it. Keep the gateway on your Wi-Fi, and fix it as soon as the app stops updating.
• Changes at your home. New shade (a tree you planted, an addition) or work on the roof can void the guarantee for the lost power. Sunrun's disclosure says so plainly.
• Your share of the problem. Switching the system off, or letting someone other than the company work on it, can count against you.

If you're owed money

1. Write down the numbers: the guarantee period's dates, the estimate, the guaranteed share and the production for exactly those dates (a screenshot of the app helps).
2. Send the claim in writing to the address in the "Notices" section of your contract, and keep a copy. The letter in the result above has the numbers filled in.
3. Ask for a repair too. A refund pays for the lost power, but the company that owns the system is also responsible for fixing it.
4. No answer? See what to do when the leasing company won't answer.

Not sure the system is underperforming? Check it against what it should make, by year or for a single month.

Sources: SunPower: lease performance guarantee FAQ; Sunrun: example solar disclosure document (90% performance guarantee); Sunrun: example PPA with a 100% performance guarantee; Tesla: how leasing solar panels works.