Solar Payback Calculator by State
Pick your state and the tool fills in typical sun, electric rates, installed price and net metering for you. Size the system from your bill, see the panels on a 3D roof, then read your payback years and 25-year savings. Every number can be edited.
- System—
- Year-1 power—
- Payback—
- 25-year net—
Panels sit on the south slope at about 400 W each · yellow arcs show the summer, spring/fall and winter sun for your state · drag to turn, scroll or pinch to zoom
Cash-flow chart when the system has paid for itself
The line starts at what you pay after incentives and climbs by each year's savings. It crosses zero at payback.
How this solar calculator works
Production: yearly kWh = system kW × the kWh per kW for your state × roof direction (south 100%, southeast or southwest 95%, east or west 85%, flat roof with tilted racks 90%) × roof steepness (typical 100%, low 97%, steep 95%) × shade (none 100%, light 92%, moderate 80%, heavy 65%). The state values come from NREL PVWatts and the NSRDB sunshine database for one representative city per state, for a south-facing roof at 25 degrees with 14% system losses. Your own roof, shade and tilt change this, so run your address through PVWatts or ask installers for a shade-adjusted model.
Savings: with full net metering, each kWh you make offsets one you would buy, up to your yearly use. With a reduced credit or buyback, power you use as it is made saves your full rate and power you send out earns the lower export rate. Rates rise by your yearly escalation, and panel output drops by your yearly loss. The tool adds the savings year by year, subtracts them from what you paid, and reports where the running total crosses zero (simple payback) and where it stands at year 25.
Sizing: choose "Size it from my bill" and the tool picks the kW that makes year-1 production cover the share of your use you ask for (100% by default), then rounds up to whole panels. Panel count is the system size divided by the panel watts. Roof area is about 21 sq ft per 400 W panel plus 12% for spacing and walkways. Avoided CO2 uses 0.37 kg per kWh, roughly the U.S. grid average.
Loan: the optional loan box shows the monthly payment and total interest for what you borrow after the down payment. The payback and chart stay on a cash basis so you can compare quotes fairly.
Panels in 3D: the panels are laid out in rows on the south slope with rails and standoffs, and the inverter is on the wall. The sun arcs use the latitude of your state's representative city. A bigger system makes the house wider or the roof taller so the panels fit.
Federal tax credit and state rules
- Federal credit: the 30% Residential Clean Energy Credit (Section 25D) was ended by the 2025 budget law (Public Law 119-21, section 70506). By the statute it does not apply to any expenditures made after December 31, 2025, and the IRS says it is not available for property placed in service after that date. For a system you buy and own, that means one finished in 2026 or later gets no 25D credit, so this tool defaults to none. You can still type your own percentage or dollar incentive.
- Leases and power-purchase agreements: the company that owns the panels may still claim a business tax credit and pass part of it to you as a lower price. This tool does not model that, so get the numbers in writing and ask a tax professional about your own case.
- Net metering: each state is tagged with one of three levels: full retail net metering, a reduced export credit (net billing or an avoided-cost credit), or no statewide rule where the utility decides. The tags follow the NC Clean Energy Technology Center's 50 States of Solar and DSIRE. Utilities inside a state often differ and rules change every year, so use the tag as a starting point and ask your utility for its current export rate.
- Permits and the utility: you will need an electrical permit and your utility's approval to connect before turning the system on. Ask your building department and your utility.
This tool is a planning estimate, not a quote or tax advice. Real savings depend on your roof, shade, usage pattern, rate plan and equipment.
State data used sun, price, cost, policy for every state
Starting values for every state, all editable above. Yield is first-year kWh per kW on a south roof; rate is the average residential price, January to July 2026; cost is the average quoted price per watt before incentives.
| State | City used for sun | kWh per kW | Rate ¢/kWh | $ per watt | Export policy |
|---|
Yield: NREL/NLR PVWatts v8 (AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL) and the EU JRC PVGIS 5.2 tool using the same NSRDB sunshine data (all other states), both for a 25 degree south-facing roof with 14% system losses; the two matched within about 4% where both were run. Rate: EIA Electric Power Monthly Table 5.6.B (July 2026 year to date). Cost: EnergySage marketplace data updated September 25, 2026; Alaska is our estimate. Policy tags: NC Clean Energy Technology Center, 50 States of Solar, and DSIRE.
Sources
- IRS, Residential Clean Energy Credit (not available for property placed in service after December 31, 2025)
- 26 U.S. Code § 25D, Residential clean energy credit (subsection (h): no credit for expenditures made after December 31, 2025)
- NREL / NLR PVWatts Calculator (kWh per kW per year; 14% default system losses)
- European Commission JRC, PVGIS 5.2 (NSRDB radiation database for the Americas)
- NREL National Solar Radiation Database (NSRDB)
- EIA, Electric Power Monthly, Table 5.6.B, average price of electricity by state, year to date through July 2026
- EIA, Electric Power Monthly, Table 5.6.A (monthly)
- EnergySage, solar panel cost by state (updated September 25, 2026)
- Lawrence Berkeley National Laboratory, Tracking the Sun (U.S. median installed price about $4.00 per watt in 2024)
- NC Clean Energy Technology Center, The 50 States of Solar, Q2 2026
- DSIRE, Database of State Incentives for Renewables and Efficiency
- Public Utility Commission of Texas, Thinking about solar panels for your home? (net metering and buyback)
- U.S. EPA, eGRID (grid emission rates used for CO2 avoided)
- U.S. Census Bureau Geocoder (optional address to state lookup)
Estimates only — not engineering, legal or code advice. Check requirements with your local building department and a licensed professional before you build.
Common questions
Is there still a federal tax credit for home solar?
Not for a system you buy. The 30% Residential Clean Energy Credit (Section 25D) was ended by the 2025 budget law (Public Law 119-21). The statute says it does not apply to expenditures made after December 31, 2025, and the IRS says it is not available for property placed in service after that date. A system finished in 2026 or later gets no 25D credit, so this tool starts at no federal credit. Leases and power-purchase agreements are different: the company that owns the panels may still claim a business credit and pass part of it on. Ask a tax professional about your own case.
How does the tool use my state?
Each state sets four starting values you can edit: yearly output per kW of panels from NREL PVWatts and NSRDB sunshine data for one representative city (for example 1,450 kWh per kW in Texas, 1,780 in Arizona and 1,140 in Washington), the average residential electric price from the U.S. Energy Information Administration (16.06 cents per kWh in Texas, 33.25 in California, 14.40 in Washington), the average quoted installed price from EnergySage ($2.25 per watt in Texas, $2.52 in California, $2.51 in Washington), and the state's net metering type. A big state has more than one climate, so change the yearly output if your area differs.
What is net metering, and does my state have it?
Net metering means the utility credits the extra power your panels send to the grid at or near the price you pay for power. Many states, such as New York and Washington, still use full retail net metering. Others, such as California and Arizona, pay a lower export credit. Texas has no statewide rule, so your electric provider decides what it pays, often around 7 cents per kWh. The tool tags each state with one of those three levels from the NC Clean Energy Technology Center and DSIRE, but utilities in the same state can differ, so ask yours.
How long will solar take to pay for itself?
With the starting values and a $180 monthly bill, the tool sizes the system to match your use. In Texas that is 24 panels (9.6 kW) at $21,600 with no federal credit, saving about $1,605 in year 1 for a payback of about 12.3 years. In New York the same bill buys 15 panels (6.0 kW) for $16,500 with a payback of about 6.9 years, because power there costs 29.38 cents per kWh and net metering credits your extra power in full. Your roof, shade, rate plan and quotes will change this.
How many panels do I need, and how much roof?
Divide the system size by the panel watts. A 9.6 kW system is 24 panels of 400 W. To size from your bill, the tool turns the bill and your rate into yearly kWh, then divides by the yearly output per kW for your state, adjusted for roof direction, steepness and shade. It also shows roof area, about 21 sq ft per panel plus 12% for spacing, so 24 panels need about 567 sq ft of usable roof.
How much do solar panels lose each year?
This tool assumes the panels produce 0.5% less each year, a common warranty and planning value. Over 25 years that is about an 11% drop from year one, and the tool applies it before it adds up your savings. You can change it.
Does a battery make solar pay back faster?
Usually not. Where extra power earns a low export credit, a battery lets you use more of your own solar at your full rate, but a home battery typically costs $700 to $1,300 per kWh installed, so the extra savings often do not cover its cost. People buy batteries mostly for backup power in outages, which this tool does not price.