Home solar
How much of your EV charging can come from your own roof?
Pick your car and an array size. We use the model’s verified efficiency to calculate how many kWh of charging the panels cover, what that saves at your tariff, and how long the system takes to pay for itself.
Reference values: 4.2 US average, 3.3 northern France, 4.3 Portugal, 4.6 Brazil. Peak sun hours are not daylight hours.
- Solar-covered driving
- 3,780 mi
- Annual generation
- 7,910 kWh
- Annual saving
- $1,096
- Simple payback
- 11.0 years
- Net saving over 25 years
- $15,389
- Panels (400 W)
- 15
- CO₂ avoided per year
- 2,769 kg
- For 100% daytime coverage
- 1.2 kWp
Assumes 86% system yield, 90% charging efficiency, 400 W panels and a 25-year life. Savings are not indexed to energy prices and no subsidy is added beyond the cost you enter, so they stay conservative.
Estimate only. Roof orientation, shading, tariffs and installation costs vary — get a site survey before buying.
How the maths works
- 1 EV energy need = annual distance ÷ verified efficiency ÷ 90% charging efficiency.
- 2 Generation = array size × peak sun hours × 365 × 86% system yield.
- 3 On-site solar = generation × the share used at home; the car takes the smaller of daytime charging and that share.
- 4 Savings = on-site kWh × retail price + exported kWh × export rate.
- 5 Payback = installed cost ÷ annual saving; the 25-year net subtracts the capex.
Solar and EV questions
How many solar panels do I need to charge an electric car?
An EV driving 15,000 km a year needs about 2,600 kWh at the meter. At 4 peak sun hours a day, roughly 2 kWp — five 400 W panels — covers that in theory; in practice most homes install 6–10 kWp and use the surplus for the house.
Can I charge my EV from solar at night?
Not directly. Night charging comes from the grid or a home battery. Without a battery, the solar share depends on how often the car is plugged in during daylight.
Does a bigger array always pay back faster?
No. Past the point where generation exceeds daytime charging and household use, extra kWh are exported at a lower rate, which lengthens payback.
Is this calculator specific to my car?
Yes — efficiency comes from the same verified dataset used on the car pages, so a Model Y and a Rivian R1S get different answers for the same mileage.
Check your car’s charging numbers
The same verified efficiency powers the charging time and cost calculator on every car page.