GuaranteeCheckDefinition
A solar production guarantee is your lease or PPA's promise that the system will produce at least a stated amount of electricity. A true-up is the periodic comparison of what the system actually produced against what was guaranteed. If production came up short, the agreement calls for a shortfall credit at a stated rate per kilowatt-hour (kWh).
The cycle
Timing depends on your agreement. Our research found that SunPower-era leases true up on a fixed cycle, commonly every 24 months. Sunrun's BrightBuy with Protection Plus agreement ties its refund to each in-service anniversary instead. Because true-ups come this rarely, a claim only comes up every year or two, and it is easy to miss.
Surplus carryover
If your system produced more than the guarantee in one period, that surplus generally carries forward and offsets a shortfall in a later period. It is not paid out on its own. So a shortfall this period only counts to the extent it is bigger than any surplus you carried in.
Worked example (HYPOTHETICAL)
This example is made up to show the arithmetic. It is not anyone's real contract, and your numbers will differ. Assume a lease guarantees 8,000 kWh per year, trues up every 24 months, and pays $0.20 per kWh of shortfall.
Hypothetical figures only. Most true-up periods show no shortfall at all, and our research expects a typical payout, when one exists, to be in the low hundreds of dollars.
What to do with this
Find your annual guaranteed production, the true-up cycle and the per-kWh rate in your own agreement, then follow how to check whether your guarantee was met. The exact formula GuaranteeCheck uses is on the methodology page.
Want the math run for you? See how the free diagnostic works, or see pricing. Common questions are answered on the FAQ.