Estimate your rooftop solar production, savings, and payback before you talk to an installer
Run your solar estimate
Pick a state preset, adjust sun hours and rate to match your bill, enter a quoted system size and cost, and see estimated production, savings, net cost, payback, and 25-year savings instantly.
Solar Savings Calculator
Estimate what rooftop solar could produce and save at your home. All figures below are estimates based on the values you enter and state-average preset data.
Estimates only, based on state-average sun hours and electricity rates. Actual production and savings vary by roof, shading, equipment and utility rules.
Get your results by email
Want to keep a copy of your numbers? After you run the calculation, use the "Email me my results" button on this page to have your results sent to your inbox. When you request your results by email, we may also follow up with a short consultation about your situation and how the numbers could be improved — no obligation, and you can ignore or decline the follow-up at any time.
About this tool
Going solar sounds simple until the quotes arrive: one installer recommends a 7 kW system, another pushes 10 kW, and both promise savings that are hard to check. This Solar Savings Calculator gives you an independent estimate first, before any sales conversation, using the same basic physics every proposal relies on. Pick your state to load a state-average estimate for peak sun hours and residential electricity price, then adjust those numbers to match your actual utility bill and roof. Enter the system size in kilowatts and the quoted cost, and choose whether to apply the 30 percent federal tax credit as a current-law assumption. The calculator then estimates annual production with a standard 0.85 derate for inverter losses, heat, wiring, and soiling, multiplies that production by your rate to estimate annual savings, and works out net cost, simple payback in years, and estimated savings over 25 years. High-rate states can pay back surprisingly fast even with modest sun, while low-rate states with excellent sun may take longer than brochures suggest, which is exactly why seeing both inputs side by side matters. Use the result to compare quotes on equal terms, question outliers, and decide whether a site visit and detailed shade analysis are worth your time.
How it works
- Choose your state preset or enter your own peak sun hours per day and electricity rate in dollars per kWh from a recent utility bill.
- Enter the proposed system size in kW and its total cost before credits, then toggle the 30 percent federal tax credit assumption on or off.
- The engine estimates annual production as system kW times sun hours times 365 times a 0.85 derate factor, then multiplies production by your rate to estimate annual savings.
- Read the estimated net cost, simple payback period, and 25-year savings, and re-run the numbers for each installer quote to compare them fairly.
Frequently asked questions
How accurate is this solar estimate?
It is a planning estimate, not a production guarantee. It uses state-average sun hours and the rate you enter with a standard 0.85 derate, but it does not model your roof angle, azimuth, shading from trees or chimneys, panel degradation, net metering rules, or future rate changes. A detailed installer design with shade analysis will be more precise for your specific roof.
What does the 0.85 derate factor mean?
Nameplate kW assumes ideal laboratory conditions. In real operation, inverters, wiring, heat, dust, and mismatch lose some energy, so this calculator multiplies ideal production by 0.85. That is a common planning assumption for an estimate; your actual system losses could be higher or lower depending on equipment and installation quality.
Does the calculator give tax advice about the federal credit?
No. The checkbox simply applies a 30 percent reduction to system cost as a current-law assumption so you can see its effect on payback. Eligibility, timing, and how the credit applies to your taxes depend on your personal situation and current law, so confirm details with a qualified tax professional before relying on it.
Why do payback results differ so much by state?
Payback depends on both sunshine and price. A state with fewer sun hours but very high electricity rates can save more per kWh produced than a sunny state with cheap power. That is why the preset table pairs each state sun-hours estimate with a state-average rate estimate, and why entering the rate from your own bill improves the estimate.
What system size should I enter?
Start with the size or sizes installers have quoted you, or estimate from your annual electricity use: divide your yearly kWh by the estimated production per kW shown for your state. Oversizing beyond what your utility credits you for may not improve savings, so check your utility net metering or export rules.