Methodology

Estimates combine average residential electricity prices (U.S. EIA), solar production per kW at each city's coordinates (NREL PVWatts), typical installed cost per watt, and each state's export-credit rules. Savings assume 90% bill offset, 3% annual rate increases and 0.5% panel degradation per year.

Formula

• Annual use = monthly bill ÷ rate × 12. System size = annual use × 0.9 ÷ production per kW.
• Self-consumed share (60%) is valued at retail. Exported share (40%) is valued at retail × the state's export-credit factor (full 1.0, partial 0.6, varies 0.5, low 0.25).
• Payback is the first year that cumulative savings exceed cost before incentives. State incentives are listed but not subtracted.

Sources

• EIA electricity data by state
• NREL PVWatts v8
• DSIRE incentive database

Independence

We are paid by installers when you ask us to connect you with them. That never changes the numbers. Rankings and estimates are not sold.