Solar Payback Period Explained: What Sets the Number
Solar payback depends on cost, output, price, export credit and self-use. See real examples by state and why a bigger system is not always better.
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Official data: EIA · DOE · IRS · how we check
In this article · 10 sections
Short answer
Solar payback period is the number of years it takes for your bill savings to equal what you paid for the system. Five things set that number: what the system costs, how much it produces, what your electricity costs, what your utility pays for power you send back, and how much of your solar power you use yourself.
Price per kWh (kilowatt-hour, the unit your bill uses) matters most. In our example home, payback runs from 4.1 years in Hawaii to 17.2 years in Washington. Your own quote and your own utility rules decide where you land.
The example home we use
All numbers below come from one example home, so the comparisons are fair:
- 7 kW system, installed cost $3000 per kW ($21000 total)
- 10500 kWh of use per year, with 40% of that use while the sun is up
- No incentives, $100 per year maintenance
- Electricity price rising 2.5% per year, panels losing 0.5% of output per year
- 25-year horizon
- Export credits capped at a year of grid purchases (annual true-up)
Output comes from PVWatts, a free solar estimator from the U.S. Department of Energy's National Laboratory of the Rockies (formerly NREL). We use a south-facing roof, 20° pitch and 14% system losses, with one reference city per state. See our methodology for details.
Factor 1: Cost
Payback is simple division: cost divided by yearly savings. If the price goes up and savings stay the same, payback gets longer. Cost per kW is the number to compare when you read quotes.
Incentives change this a lot. The 30% federal Residential Clean Energy Credit (Section 25D) is not available for property placed in service after December 31, 2025. Our example uses no incentives. State and utility programs vary, and DSIRE (programs.dsireusa.org) keeps a database of current ones. Our guide on solar without the tax credit goes deeper.
Factor 2: Output
The same panels make more power in sunny places. Yearly output per kW in our data:
| State (city) | Output per kW per year |
|---|---|
| Arizona (Phoenix) | 1755 kWh |
| California (Los Angeles) | 1677 kWh |
| Texas (Houston) | 1421 kWh |
| Illinois (Chicago) | 1308 kWh |
| Washington (Seattle) | 1088 kWh |
More output means a smaller system can cover your use. To produce 10500 kWh per year, you need about 6 kW in Arizona, 7.4 kW in Texas and 9.7 kW in Washington. Our guide on how many solar panels you need explains the sizing step by step.
Factor 3: Electricity price
Every kWh your panels make saves you the price you would have paid. A higher price shortens payback, even where the sun is weaker. The U.S. average residential price was 18.31¢/kWh in July 2026, against 17.45¢ a year earlier (EIA).
Look at how price beats sunshine:
| State (city) | Output per kW | Price | Payback (full credit) |
|---|---|---|---|
| Hawaii (Honolulu) | 1622 kWh | 48¢/kWh | 4.1 years |
| California (Los Angeles) | 1677 kWh | 33.61¢/kWh | 5.8 years |
| Massachusetts (Boston) | 1302 kWh | 30.49¢/kWh | 7.3 years |
| Arizona (Phoenix) | 1755 kWh | 15.38¢/kWh | 12 years |
| Nevada (Las Vegas) | 1753 kWh | 12.77¢/kWh | 14.1 years |
| Washington (Seattle) | 1088 kWh | 14.71¢/kWh | 17.2 years |
Boston gets less sun than Phoenix, yet its payback is much shorter because power costs about twice as much there. Check electricity prices by state and see electricity prices and solar payback for more. The EIA publishes these prices monthly in the Electric Power Monthly, Table 5.6.A. Recent months are preliminary.
Factor 4: Export credit
When your panels make more than your home uses, extra power goes to the grid. What you get for it depends on your utility. Under net metering, you often get a credit close to the retail price. Under net billing, the credit can be lower. Rules vary by state and utility.
We test three cases. "Full credit" means exports earn the full retail price. "Half credit" and "quarter credit" mean exports earn half or a quarter of it.
| State (city) | Full credit | Half credit | Quarter credit |
|---|---|---|---|
| California (Los Angeles) | 5.8 years | 7.6 years | 9.7 years |
| Texas (Houston) | 12.5 years | 17 years | 20.5 years |
| New York (New York City) | 7.5 years | 10.1 years | 12.1 years |
| Illinois (Chicago) | 11.3 years | 15 years | 17.9 years |
| Washington (Seattle) | 17.2 years | 21.8 years | 25 years |
Texas moves from 12.5 years to 20.5 years just by changing the credit. That is a bigger swing than most differences in panel brand. Read net metering vs net billing and ask your utility how it credits exports.
Factor 5: Self-consumption
Self-consumption means using your solar power in your home as it is made. In our example, 40% of use happens while the sun is up. That share is power you offset directly, at full retail price. The rest depends on export credits.
You can raise your share by running the dishwasher, laundry or EV charging during the day. A home that is empty all day, with a large system, exports more and depends more on the credit rule.
Why a bigger system is not always better
Our model caps export credits at a year of grid purchases. Once your system covers your yearly use, extra panels earn nothing more, but they still cost money. Look at Texas:
| System size | Cost | Year-1 savings | Payback |
|---|---|---|---|
| 3 kW | $9000 | $677 | 13.5 years |
| 5 kW | $15000 | $1129 | 12.8 years |
| 7 kW | $21000 | $1580 | 12.5 years |
| 9 kW | $27000 | $1667 | 14.4 years |
| 12 kW | $36000 | $1667 | 18.2 years |
Past 7 kW, savings barely rise but cost keeps climbing. California shows the same shape: 5.3 years at 5 kW, 5.8 years at 7 kW and 9.4 years at 12 kW. The 25-year gain in Texas peaks around 9 kW at $27455, with 7 kW close behind at $27028. Match your system to your yearly use, not to your roof size.
How to estimate your own payback
- Get your yearly kWh use from your bill.
- Find your price per kWh, including fees if you can.
- Ask your utility how it credits exported power.
- Get a written quote, then divide cost by estimated yearly savings.
- Try the solar calculator with your numbers, and compare with our state pages.
Payback is only an estimate. Roof shade, direction, rate plans and future price changes can all move it. Treat any single number, ours included, as a starting point.
Bottom line
Payback is not set by sunshine alone. Electricity price and export credit often matter more than location. In our example, it runs from 4.1 years in Hawaii to 17.2 years in Washington, and from 12.5 to 20.5 years in Texas depending on the credit. Size the system to your use, ask your utility about export rules, and compare quotes per kW. Then run your own numbers in the solar calculator.
Sources
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