Rooftop solar pays back when the electricity it displaces is worth more than the loan-free cost of installing it — and the retail rate you avoid matters more than the price of the hardware. California, 30% federal credit Installed system cost, before incentives 18000 USD
Incentives and credits, share of cost 30 %
Retail electricity rate avoided 0.17 USD/kWh
Years to break even 7.79
Lifetime net savings 27,850
Panel lifetime: past here, no payback Ten years — typical inverter replacement Payback years Caveat Payback is computed in flat, undiscounted dollars: no financing cost, no rate escalation, and no panel degradation, which runs roughly 0.5% of output per year. It also assumes every kilowatt-hour produced offsets one bought at the full retail rate, which is generous wherever net metering has been replaced by an export tariff.Interactive artifact by Delineo