All calculators
Audit your solar proposal — one tool at a time.
Six calculators that test the math the salesperson didn't bring to the kitchen table. Start with the quote calculator if you have a proposal in hand. Start with the panel calculator if you don't.
Start here
Have a quote? Run the full quote calculator first. No quote yet? Size the system first. Confused by monthly payment? Use the loan calculator before the payback calculator — the loan structure can change every other number.
Updated May 16, 2026.
Solar quote calculator
Type in the numbers on your proposal. Every line benchmarked against NREL, LBNL, EIA, and IRS public data. Flags the math that doesn't survive scrutiny.
Solar panel calculator
How many panels you actually need for your roof and your annual usage — not how many the salesperson can fit.
Solar payback calculator
Year-by-year payback math with the four assumptions visible. Move the escalator. Watch the year shift.
Solar loan calculator
Strip the financing markup out of the cash price. Find out what the loan really costs, against LBNL's 5-50% documented range.
Solar tax credit checker
The federal credit ended for systems placed in service after Dec 31, 2025. This checker resolves whether your specific install year + ownership model qualifies.
Solar battery calculator
Decompose battery value into TOU arbitrage savings and outage-resilience value. Most proposals stack both. We separate them.