Estimate solar panel cost, payback period, and 25-year savings using EIA rates, NREL solar data, and current IRS guidance. The model turns four simple inputs into a transparent baseline you can compare with installer quotes — no email, no lead capture, no installer affiliation.
Estimate a state-average solar planning baseline from published electricity-rate and solar-resource data. Not an installer quote, engineering assessment, tax determination or utility-specific savings forecast.
Fill in the four fields on the leftabove and we'll show payback, net cost, and a 25-year savings curve.
Computing your projection…
2.9%/yr electricity inflation · 0.5%/yr panel degradation · Curve crosses zero at payback.
Every formula and constant is published, sourced, and re-derivable in a spreadsheet.
A $180 bill at California's $0.31/kWh implies ~6,968 kWh/year — consistent with EIA's 6,500 kWh CA average.
The 0.80 is the industry "performance ratio" — losses from inverter, wiring, temperature, and soiling, per NREL PVWatts.
Berkeley Lab Tracking the Sun 2025: the median price cash purchasers actually paid, across 18,361 systems. Not a quote average — transactions.
IRS guidance says the Section 25D Residential Clean Energy Credit is not available for new expenditures after December 31, 2025.
Most "free solar calculators" exist to capture your contact details for installer leads. This one doesn't.
We don't capture your email or sell anything you type. There are no advertising or lead-generation trackers. Google Analytics is the one third-party script here and it does not load unless you allow it — see privacy. The only future revenue source is non-targeted display advertising via Google AdSense — and only after we earn a real audience.
EIA, NREL, IRS, DSIRE. No proprietary "secret sauce".
Audit our math line by line. CC BY-SA 4.0 license.
Most calculators give you a single payback number. Ours shows the full cumulative-savings curve, with electricity inflation and panel degradation modeled explicitly, so you can see what year three actually looks like.
Every constant change is dated and explained.
A complete inventory of every data point that touches our server when you run a calculation.
You've received one or more bids and want a defensible independent baseline for cost-per-watt and payback.
Cash, solar loan, or PPA — the 25-year cumulative curve is the right denominator. We show it explicitly.
Energy-economics students, policy analysts, and journalists who want a source-cited baseline for US residential solar.
The questions a knowledgeable reader actually asks.
A generalised, four-input model cannot reproduce the precision of a site-specific engineering study. These are explicitly outside our scope:
For any of these, the right next step is a licensed installer's site assessment plus an independent review against your utility's tariff sheet.
Every state guide links local electricity rates, peak sun hours, incentive notes, and the calculator workflow.
Four inputs. Sixty seconds. Every number traceable to a public source.
May we count this visit? If you allow it, Google Analytics counts calculator use among visitors who agree — so it measures that group, not our total traffic. It sets a cookie and Google receives your IP address. It is not loaded unless you agree, and the calculator works either way — we do not send it your bill, ZIP code or results. What we collect.