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Solar cost calculator

Independent estimate of system size, installed cost, payback period, and 25-year ROI. No email. No sales call.

Methodology: EnergySage cost/watt data · NREL solar irradiance · US EIA electricity rates · Last updated March 2026
Methodology: System size estimated from your monthly bill and state electricity rate (EIA data). Install cost from EnergySage quarterly cost-per-watt averages, adjusted for roof type. Savings calculated at 90% bill offset with 3% annual electricity inflation. 25-year ROI compounds savings against net cost after ITC, with 0.5%/yr panel degradation.

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Your estimate
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System size — kW Estimated solar array
Gross install cost — Before any incentives
Net cost (after 30% ITC) — Federal tax credit applied
Annual savings — Year 1 electricity savings
Payback period — Years to break even
25-year ROI — Estimated total return

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How this works

Calculation methodology

System size

We estimate your monthly electricity consumption (kWh) from your bill using state average electricity rates from US EIA monthly data. We then divide annual consumption by the product of state peak sun hours (from NREL's PVWatts state database) times 365 times a 0.8 efficiency factor to arrive at the required array size in kW.

Install cost

Based on EnergySage's quarterly state-by-state cost-per-watt averages, derived from their installer quote marketplace. A multiplier is applied for non-standard roof types (tile, metal, flat) based on industry-reported install complexity premiums.

Annual savings

We assume the system offsets 90% of your annual electricity consumption, accounting for system losses. Savings are calculated at your state's current electricity rate with a 3% annual escalator, consistent with EIA long-term electricity price projections.

25-year ROI

Net cost after the federal ITC (30%) is subtracted from cumulative savings over 25 years. Savings are escalated at 3% per year for electricity price inflation and reduced at 0.5% per year for panel degradation, consistent with industry-standard assumptions.