Understanding regional payback differences
Why California beats sunnier regions
California, despite only moderate sun hours, produces the fastest typical payback of the six regions here, about 7.0 years for a 6.5 kW system with no federal tax credit, the accurate 2026 default. With the historical 30% credit, that drops to about 4.9 years. The reason is rate, not sun: California's utility rates run around $0.30 per kWh, more than double the Southwest's roughly $0.14, so each kWh of production is worth significantly more even with somewhat less sunshine. If you have not sized the system yet, start with the system size by monthly kwh usage and bring its kilowatt figure back here.
Sun hours alone don't determine payback
The Southwest gets the most sun of any region here, at 6.2 peak hours a day, yet its payback of about 13.4 years at the current 0% federal credit default trails California by a wide margin. Savings depend on production multiplied by rate, and a high rate can outweigh a sun hours advantage, or the reverse. The Pacific Northwest combines both lower sun and lower rates, landing at the slowest payback of roughly 25.4 years. With the historical 30% credit, those figures fall to about 9.3 and 17.8 years respectively. The production figure behind this estimate comes from the peak sun hours calculator, which models output for your location and roof.
These are averages, not your exact numbers
Regional figures smooth over real variation within each region. Your specific utility, rate plan, roof orientation, and shading all affect your actual numbers. Use this tool to get a general sense of how your part of the country compares, then run your specific address details through the solar savings calculator for a more precise figure, or check time of use rate savings if your utility bills by time of day. For the official overview, the US Department of Energy's homeowner's guide to going solar covers buying, leasing, and system sizing.
State incentives beyond the federal credit
This tool defaults to 0% for the federal tax credit, since the 30% residential credit expired for systems placed in service after December 31, 2025. You can still model the historical 30% rate if your system was installed by that date. Many states layer additional rebates or incentives on top of either scenario, which would shorten payback further in those states specifically. Check the savings with ITC applied calculator to see the federal credit's effect in isolation, then research your state's specific programs separately. The DSIRE database of state incentives lists the incentives that apply in your state, with links to each program's rules.