The same 6kW system, the same roof, the same sun — but a very different payback period depending purely on who bills you for electricity.
Higher rates mean faster payback, all else equal
Every kWh your system produces is worth more when your utility charges more for it — which is why a system in San Diego Gas & Electric's territory, with among the highest rates in the country, tends to pay back faster than the identical system on a utility charging half as much. See our SDG&E versus NV Energy rate pages for a concrete sense of how different two real utilities can be.
Net metering terms compound the effect
A utility offering full retail-rate net metering credits every exported kWh at full value; a utility with a lower export rate or tiered structure pays less for the same exported energy. Combined with the base rate difference, two utilities can produce genuinely different payback periods for identical systems — see how net metering varies by state for the policy side of this.
Municipal utilities can differ sharply from investor-owned ones nearby
Sacramento's SMUD, LADWP in Los Angeles, and Salt River Project in the Phoenix area are all municipal or public utilities with rate structures genuinely different from the investor-owned utility serving the surrounding region — worth checking specifically which utility serves your address, not just assuming a general area rate applies.
Run your specific numbers, not a national average
A national average payback figure smooths over all of this real variation. Use your specific utility's rate (check the rate tracker for a starting point, then your actual bill for precision) in the solar payback calculator for a number that actually reflects your situation.
Frequently asked questions
Which matters more for payback — electricity rate or sun hours?
Both matter, but rate differences between utilities can be larger in percentage terms than sun-hour differences between reasonably sunny regions — a high-rate, moderate-sun area can outperform a low-rate, high-sun area on payback speed.
How do I find out exactly which utility serves my address?
Check a recent electric bill, which will show the utility name directly — in areas with multiple utilities serving nearby but distinct territories (like Phoenix or Los Angeles), don't assume based on the general region alone.