Solar Payback Calculator
Work out the system size your bill actually needs, what it costs, what it saves each year, and the year it breaks even.
Estimates, not a quote. Real output depends on your roof pitch, orientation, shading and local weather, and savings depend heavily on your utility's net metering terms — which vary by state and have been getting less generous. Get quotes from installers and confirm your utility's current tariff before committing.
Average across the year, not a summer peak.
Residential commonly runs $2.50–$3.50 per watt before incentives.
The residential solar credit (Section 25D) expired. The One Big Beautiful Bill Act ended it for systems placed in service after December 31, 2025 — with no phase-down. A 2026 cash or loan purchase gets $0 federal credit. If your system was completed in 2025 you can still claim it on that year's return. State and utility incentives still exist — enter yours below.
Payback in
Enter your bill
| Detail | Amount |
|---|---|
| System size | — |
| Annual production | — |
| Cost before incentives | — |
| Net cost after credit | — |
| Annual savings | — |
| 25-year net position | — |
How Solar Payback Is Calculated
- Your usage. Monthly bill ÷ rate × 12 = kilowatt-hours per year.
- System size. Annual kWh ÷ your region's production factor = kW needed. That factor is how many kWh each installed kW produces in a year where you live — about 1,100 in the cloudy Northeast, up to 1,600 in the desert Southwest.
- Cost. kW × 1,000 × price per watt, then subtract any state or utility rebate. The 30% federal credit no longer applies to systems placed in service after December 31, 2025.
- Payback. Net cost ÷ annual savings. The 25-year figure assumes roughly 0.5% annual panel degradation against ~2.5% annual utility rate inflation.
Worked example — $180/month bill at $0.17/kWh, average sun, $3.00/watt: 12,706 kWh/yr → about a 9.8 kW system, $29,321 gross, $20,525 after the credit, saving ~$2,160 in year one → payback around year 8.8, and roughly +$48,500 over 25 years.
Simple division would say 9.5 years. The calculator returns 8.8 because it models each year separately — utility rates historically rise faster (~2.5%/yr) than panels lose output (~0.5%/yr), so later years save more than the first one.
What Moves the Number Most
| Factor | Effect on payback |
|---|---|
| High electricity rates | Biggest single lever. Expensive power is what makes solar pay |
| Full retail net metering | Large improvement; wholesale-only export rates can add years |
| Regional sunshine | Southwest vs Northeast is roughly a 45% swing in output |
| Roof orientation & shade | South-facing unshaded is the benchmark; east/west costs 10–20% |
| Adding a heat pump or EV | Raises usage — size the array for future load, not today's bill |
The Honest Caveats
- Net metering is the variable nobody mentions. Where utilities pay full retail for exported power, the math above holds. Where they pay wholesale, savings can drop by a third or more. Check your utility's current tariff, not last year's blog post.
- The federal credit is gone for 2026 purchases. Section 25D ended December 31, 2025 with no phase-down, so budget the full installed price. If a salesperson still quotes you a 30% federal credit on a 2026 install, that is a red flag worth pushing back on.
- Leases and PPAs are a different rule. Third-party-owned systems fall under a separate business credit (48E) that runs longer, which is why some installers now push leasing. A lease is not ownership — compare the lifetime numbers, not just the monthly payment.
- Payback ≠ the whole story. Solar has the longest payback of the common efficiency upgrades — 6–10 years versus 3–6 for attic insulation — but the largest cumulative savings over 25+ years.
- Do the cheap things first. Insulation and air sealing reduce the load you're about to buy panels to cover. Shrinking the bill before sizing the array is almost always the better order.
- Leases and PPAs are different products. This calculator models buying. Third-party ownership changes the economics and complicates selling the house.
Frequently Asked Questions
How long does solar take to pay off?
Typically 6–10 years, with the biggest cumulative savings across a 25-year life.
What size system do I need?
Annual kWh ÷ your region's production factor (1,100 cloudy → 1,600 desert). A 12,000 kWh home needs roughly 9–11 kW.
What does home solar cost?
$25,000–$40,000 installed before incentives, about $2.50–$3.50 per watt. A $30,000 system nets near $21,000 after the credit.
Is the 30% solar credit still available in 2026?
No. Section 25D expired December 31, 2025 under the One Big Beautiful Bill Act, with no phase-down — a 2026 purchase gets $0 federal credit. Systems placed in service by the end of 2025 can still be claimed on that year's return. State and utility incentives still apply.
Does solar pair with a heat pump?
Very well — but size the array against your post-heat-pump usage or it'll be undersized immediately.
What is net metering?
Credit for power you export. Full retail is great; wholesale-only export rates lengthen payback significantly. It's set state by state.
References
- PVWatts (National Laboratory of the Rockies, formerly NREL) — modeled solar production by location: pvwatts.nlr.gov
- US Department of Energy — homeowner's guide to going solar: energy.gov
- ENERGY STAR — federal tax credits including the solar ITC: energystar.gov
- DSIRE — state incentives and net metering policy by state: dsireusa.org