Is the 25-year figure profit?

It is net of everything the model knows about: the system, maintenance every year, and an inverter replacement in year twelve are all already subtracted. It is not net of tax on any incentive payment, of a roof replacement during those 25 years, or of the cost of borrowing if you finance. For the financed case, use the lease-versus-buy calculator instead.

Because that is the term of a typical panel performance warranty, so it is the period a manufacturer is willing to stand behind. Panels usually keep producing after it at a slowly declining output; the model stops there rather than claim savings from years nobody guarantees.

Why does the yearly saving grow?

Two forces pull against each other. The panels lose about half a percent of output a year, which shrinks the saving. Electricity prices rise, which grows it. At any plausible escalation rate the second wins comfortably, so the saving climbs — and the later years, the ones furthest from anything anyone can verify, carry the most weight in the total.

What escalation rate should I use?

Nobody knows, which is the honest answer and the reason it is a slider. Our default is 2.5% a year. Set it to zero and you get the savings if electricity never gets more expensive again; that is the floor, and it is the number worth looking at before signing anything.

Calculators / Solar savings calculator

How much will solar save me?

The saving is a bill you stop paying, so it grows with the price of electricity — which is the most contested assumption in any solar calculator, and a slider here.

A saving is a bill you stop paying

That is the whole model. Each year it computes the bill you would have paid without solar and the bill you pay with it, and takes the difference. The second bill is rarely zero: the utility's fixed monthly charge survives, and in most states so does some of the electricity you buy back after dark.

Because the saving tracks the price of electricity, it grows with it. That is what makes the total so sensitive to one assumption, and why the slider sits above the results rather than in a footnote. At our default of 2.5% a year, a kilowatt-hour avoided in year 25 is worth roughly 1.8 times one avoided today.

Read the first year first

The year-one saving is the only figure here that will be tested quickly. Everything beyond it compounds an assumption. If a calculator's headline is a 25-year total and its first year is not on the page, the total is doing work the evidence cannot support. The table above starts with year one for that reason.

What is not in the total

Resale value. Research suggests buyers pay more for a house with an owned system. We do not model it: the evidence varies too much by market to compute a number we would defend.
Outage protection. Solar alone does not keep the lights on in a blackout, and a battery that does is priced in the battery calculator on the electricity it shifts, not on the inconvenience it spares you.
Rate structure changes. Your utility can move you to time-of-use pricing or change the export rule after you install. Several states we publish have done exactly that to existing customers, with grandfathering periods that eventually end.
Tax on incentive payments. Where a state pays for production, the treatment of that income is a question for a tax professional and is not modelled here.

Savings are not the same as a good investment

A large 25-year total on a large system can still be a worse use of money than a smaller one that repays sooner. The payback calculator shows the crossing point, and is solar worth it in 2026 puts both side by side across the states we publish, on one identical house.

Questions

Is the 25-year figure profit?: It is net of everything the model knows about: the system, maintenance every year, and an inverter replacement in year twelve are all already subtracted. It is not net of tax on any incentive payment, of a roof replacement during those 25 years, or of the cost of borrowing if you finance. For the financed case, use the lease-versus-buy calculator instead.
Why 25 years?: Because that is the term of a typical panel performance warranty, so it is the period a manufacturer is willing to stand behind. Panels usually keep producing after it at a slowly declining output; the model stops there rather than claim savings from years nobody guarantees.
Why does the yearly saving grow?: Two forces pull against each other. The panels lose about half a percent of output a year, which shrinks the saving. Electricity prices rise, which grows it. At any plausible escalation rate the second wins comfortably, so the saving climbs — and the later years, the ones furthest from anything anyone can verify, carry the most weight in the total.
What escalation rate should I use?: Nobody knows, which is the honest answer and the reason it is a slider. Our default is 2.5% a year. Set it to zero and you get the savings if electricity never gets more expensive again; that is the floor, and it is the number worth looking at before signing anything.

The other calculators

All of them run the same engine on the same data, so two can never disagree. They differ in what they put first.

Solar panel size calculator
How many kilowatts, how many panels and how much roof, from your bill and your state.
Solar panel cost calculator
Installed price for your system on both price bases, and what is left after credits.
Solar payback calculator
The year your savings repay the system, and the curve that gets you there.
Lease vs buy solar calculator
Cash, loan and lease on the same house, with who keeps the federal credit.
Solar battery calculator
The same system with and without storage, side by side.
Solar incentives calculator
Federal, state and performance payments for your system, each with its source.

A screening estimate from published data, not a quote and not tax or financial advice. Every input is listed under the results with the source it came from and the date it was read; the formulas are on the methodology page. Confirm against real quotes, and with a professional, before relying on any figure here.

Published 6 September 2026. Data last verified 6 September 2026. Rates: EIA 2026-07. Found a figure that looks wrong? Tell us — we publish corrections.