Solar Savings Calculator: Your Payback, Year by Year
Enter the numbers from your quote and utility bill, and the ledger does the rest: net cost after whatever incentives your purchase year still qualifies for, compounding savings, and the exact year the balance flips positive. Current defaults are set — no federal credit unless your system went in during 2025.
Planning estimate only - not tax, legal or financial advice. Confirm installed cost and current incentives with a licensed installer and the official IRS and Energy.gov sources.
How the ledger reads your inputs
Annual generation comes from your system size, your local peak-sun hours and a performance ratio that discounts for shading, wiring and inverter losses. First-year savings are that generation priced at your electricity rate, scaled by your utility’s export credit — a kilowatt-hour you push to the grid is only worth what the tariff sheet says it is. Net cost subtracts the federal treatment your purchase year qualifies for, plus any state incentive, from the gross quote. The ledger then projects 25 years, compounding your assumed rate rise, and marks the year cumulative savings pass the net cost.
Three inputs move the answer far more than the rest: the installed price in dollars per watt, your electricity rate, and the export credit on your utility’s solar tariff sheet. If you only measure three things, measure those.
Defensible defaults, so you can start anywhere
Every field ships with a neutral default: five peak-sun hours near the U.S. average, $2.80 per watt near the national installation range of 2.6–3.2, a 0.85 performance ratio typical of real roofs, and an 85% export credit between full retail and a weakened tariff. Load your state’s typical values from the state table for a sharper first look, then replace them with your quote — your numbers always beat the defaults.
Savings calculator questions
How accurate is a solar savings estimate?
It is a planning model, not a quote. The ledger uses your inputs and stated assumptions honestly, but two homes on the same street can see different results because of roof angle, shading and the exact utility rate schedule. Treat the break-even year as a first filter for the quotes you collect, not as a final number.
What do I need before running the numbers?
Three numbers carry most of the weight: the installed price on your quote in dollars per watt, your electricity rate from a recent bill, and your utility’s export credit from its solar tariff sheet. Everything else has a defensible default you can refine later.
Does this calculator include a home battery?
Battery cost is not a separate field. If your quote includes one, enter the full installed price and treat the battery as part of the package; a battery no longer changes the federal treatment, so its value shows up only in how much of your own generation you can use instead of export.
Are my numbers saved anywhere?
No server receives anything. The math runs in your browser, and your inputs stay in your own browser’s local storage so a page reload does not wipe them. Clearing site data removes them completely.