Solar + EV ROI Calculator

See how adding an electric vehicle changes your solar payback: EV charging cost, fuel savings vs gas, and the combined solar + EV payback period for your state.

How this calculator works

  • Add an electric vehicle to your solar math: enter your EV miles/year, efficiency, and how much of the charging your solar covers (daytime charging = more).
  • We compare your EV charging cost against fueling the same miles in a 28 mpg gasoline car at current gas prices.
  • The combined payback period adds your EV fuel savings to your solar savings — EVs make solar pay back faster.
Disclaimer: All figures are estimates based on public 2026 data (EIA, NREL PVWatts, DSIRE) and your inputs — not a quote, tax advice, or financial advice. The federal residential solar credit (Section 25D) expired December 31, 2025. Verify with your utility, a licensed installer, and a tax professional before signing anything.

Example scenarios

12,000 mi/yr, 70% solar charging: ~4,000 kWh of EV energy, ~$1,350/yr vs gas — typical.

High-mileage driver (20,000 mi): Fuel savings ~$2,200/yr — EVs can nearly pay for solar by themselves.

Data & algorithm

  • EV energy = miles ÷ mi/kWh. EV charge cost = energy × state rate.
  • Fuel comparison = (miles ÷ 28 mpg) × gas price.
  • Combined payback = net system cost ÷ (solar savings + EV fuel saving + solar-covered EV energy).

Official data sources

  • EIA (rates, gas price 2026), EPA (EV efficiency, 28 mpg fleet average), NREL PVWatts.

All figures dated 2026. Incentives and rates change — verify current values with your utility and the administering authority before making decisions.

Frequently asked questions

Is charging an EV with solar worth it?

Almost always — the marginal cost of solar electricity (0–5¢/kWh vs 15–30¢ grid) makes EV charging the highest-value use of your solar production. Combined payback is typically 1–3 years shorter than solar alone.

How many solar panels do I need for an EV?

An EV adds roughly 3,500–4,500 kWh/year (12,000 mi at 3.5 mi/kWh) — about 2.5–3.5 kW, or 7–9 extra 400W panels.

EV vs gas: how much do I save?

At $3.20/gal and 28 mpg, gas costs ~11.4¢/mile. At 3.5 mi/kWh and 20¢/kWh, EV costs ~5.7¢/mile — roughly half, and far less when solar covers the charge.