☀SolarSavingsMath

Solar + EV Charging Calculator

How much extra solar capacity do you need to power your EV from sunlight — and how much does it save vs charging from the grid or paying for gas? Real math for 2026 vehicles.

For sun hours, grid electricity rate, and install cost.
US average is 12,000-14,000 mi/yr per vehicle.
Average real-world efficiency, mixed driving.
Only home-charged kWh benefits from your solar.
If you have solar already, we'll size only the additional capacity needed for EV.
For grid charging comparison.
US avg ~$3.80 in 2026.
Vehicle you'd otherwise drive.
Pick your state to see how much solar you need for your EV.
Annual EV electricity needed (at home)—
Additional solar needed—
Extra panels (400W each)—
Additional solar install cost—
Net cost after 30% federal credit—

Annual driving cost comparison

⛽ Gas car

—
per year

🔌 EV on grid

—
per year

☀ EV on solar

—
per year (amortized)
Lifetime savings vs gas:

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How much solar does an EV actually need?

An electric vehicle adds significant load to your home electricity usage — but it's not as much as most people expect. The average EV driven 12,000 miles per year uses about 3,500 kWh annually. For context: that's roughly 30-35% of the typical US home's total electricity use.

To produce 3,500 kWh per year from solar requires:

The math behind it

Two simple formulas:

  1. Annual EV kWh needed = annual miles ÷ vehicle efficiency (mi/kWh)
  2. Solar capacity needed = annual kWh ÷ (daily sun hours × 365 × 0.80 efficiency)

Example for a Tesla Model Y driven 14,000 mi/yr in Texas: 14,000 ÷ 4.0 = 3,500 kWh/yr ÷ (5.3 × 365 × 0.80) = 2.3 kW solar = ~6 panels at 400W each.

Cost: solar vs grid vs gas (real numbers)

For a typical EV driving 12,000 miles/year (3,500 kWh consumed):

Energy SourceCost/kWh equivAnnual Cost
Gas car (28 MPG, $3.80/gal)~$0.45/kWh equiv$1,630
EV on grid (US avg $0.17/kWh)$0.17/kWh$595
EV on grid (CA IOU $0.36/kWh)$0.36/kWh$1,260
EV on solar (amortized over 25 yrs)~$0.04/kWh$140

The solar amortized cost is calculated by dividing the net cost of the additional solar capacity (after 30% federal credit) by the total kWh it produces over 25 years.

FAQ

How many solar panels do I need to charge an EV?

A typical EV (12,000 mi/yr, 3.5 mi/kWh) needs about 3,500 kWh/yr from your solar. At US-average sun hours that's 2-3 kW (5-8 panels). Sunny states need fewer; low-sun states need more.

Is it cheaper to charge an EV from solar or the grid?

Solar charging is 70-90% cheaper than grid charging in most states. Grid charging costs about $0.17/kWh on US average. Solar effectively costs $0.03-$0.06/kWh after amortizing the panel cost over their 25-year lifespan.

How much money does a solar-charged EV save vs a gas car?

$1,400-$1,500 per year for typical driving, plus you avoid oil changes, transmission service, and other maintenance. Over 10 years that's $14,000-$15,000 in fuel + maintenance savings, before you consider the federal $7,500 EV tax credit on the purchase.

Should I oversize my solar system when buying solar now if I'll get an EV later?

Yes. Adding panels later costs nearly as much per panel as the original install due to fixed labor, permit, and electrical interconnection costs. Sizing 2-3 kW larger now saves $2,000-$3,000 vs adding panels later.

What about charging an EV from solar at night?

Most EVs charge overnight, but solar produces during the day. Two paths: (1) you charge during the day if you work from home or have a workplace charger, OR (2) excess daytime solar exports to the grid under net metering, and you "borrow back" that energy from the grid at night. In full retail NEM states, this is 1:1 — totally cost-neutral. In NEM 3.0 (CA IOUs), this loses 75% of the value, making a home battery economically attractive.

Primary sources