Assumes $900 to install one 325 W panel — hardware, mounting, microinverter, electrical work, labour and permitting — repaid only by the electricity it avoids buying. No subsidies, tax credits, net-metering premium, financing cost or future price rises are counted, and the figure is undiscounted. Electricity price is the CA residential average (EIA, May 2026). A single panel is unusually expensive per watt because it carries a whole array's fixed costs, which is why these numbers look worse than rooftop solar generally does.
| Buildings with roofs | 13,184,204 |
| × Panel rating | 325 W |
| × Annual yield per panel here | 557.4 kWh |
| Annual generation | 7,349,342,131 kWh |