Solar payback calculator
Your ZIP code, system size and quote. We estimate yearly output, savings and the payback year.
Enter a ZIP code or choose a state.
to pay for itself
- Electricity price
- Yearly output
- System cost after rebates
- Savings in year one
- Net gain over 25 years
How we work it out
- Sunlight: NASA POWER all-sky solar irradiance climatology (2001-2025), calibrated to NREL PVWatts v8 (fixed roof array, 20 degree tilt, south-facing, 14% losses). Our estimate was within about 6% of PVWatts at eight test locations from Honolulu to Anchorage. Shade, a roof that faces east or west, or a steeper or flatter roof all change the real figure.
- Electricity price: EIA Electric Power Monthly, Table 5.6.B, residential, year to date through August 2026 (cents per kWh). We assume it rises 2% a year, and the panels lose 0.5% of their output a year.
- Installed price: median of $3.60 per watt before incentives for homeowner-owned systems ($3.00 for cash purchases, $4.50 for loan-financed), and a median system size of 7.7 kW. Source: Berkeley Lab, U.S. Distributed Solar and Storage, 2026 data update (2025 installs, host-owned, before incentives).
- Tax credit: none. The 30% federal credit for homeowners (Section 25D) ended for systems installed after December 31, 2025. Leases and power purchase agreements are priced differently and are not modeled here.
- Net metering: "Full" values every kWh at your retail rate. "Partial" assumes you use 60% of the power at home and the rest is credited at half the rate; "Low" credits exports at a quarter. Your utility's rules decide which is closest.
- Not included: batteries, financing costs, insurance, inverter replacement (often needed once in 25 years), local permits or state rebates. Get at least two written quotes before you decide.