The quick answer
Most people who drive about 35 miles a day need about 6 to 11 solar panels (400 watts each) to cover their EV's charging; most cars need 6 to 8. An efficient car like a Tesla Model Y sits at the low end. A big electric pickup sits at the high end.
Where you live matters too. A panel in sunny California makes a lot more power than the same panel in cloudy Ohio. So use the numbers below as a starting point, then plug your own car and state into our calculator.
Step 1: Work out how much energy your car uses each day
EVs are rated in kilowatt-hours per 100 miles (kWh/100 mi). It's like miles per gallon, but backwards: a lower number is better.
To get your daily number, multiply your miles by the rating and divide by 100. A car rated at 30 kWh/100 mi that drives 35 miles uses about 10.5 kWh a day. You'll find your car's official rating on fueleconomy.gov.
Step 2: Work out what one panel makes where you live
A 400-watt panel doesn't make 400 watts all day. It only gets close at midday in full sun. That's why installers use peak sun hours: the number of hours of full-strength sunlight your area gets, on average, each day.
Some power is also lost along the way, in the inverter, the wiring and on hot days. Our calculator allows 18% for these losses. So in California, with about 6.08 peak sun hours (PVWatts data), one 400 W panel makes roughly:
0.4 kW × 6.08 hours × 0.82 = about 2.0 kWh a day
Step 3: Divide one by the other
Now divide your car's daily energy by what one panel makes, and round up. That's the whole method:
Panels needed = your car's daily kWh ÷ (0.4 kW × peak sun hours × 0.82)
Here's what that looks like for two very different cars, both driving 35 miles a day in California (6.08 peak sun hours, 400 W panels, 18% system losses; panel counts rounded up):
| Car | Energy use (EPA) | Energy for 35 miles | 400 W panels needed |
|---|---|---|---|
| 2024 Tesla Model Y Long Range | 29 kWh/100 mi | 10.2 kWh | 6 panels (2.4 kW) |
| 2024 Ford F-150 Lightning 4WD Extended Range | 48 kWh/100 mi | 16.8 kWh | 9 panels (3.6 kW) |
What the numbers mean
The Model Y needs about six panels. The Lightning uses so much more energy per mile that it needs about nine. Each panel takes up roughly 20 square feet, so that's about 120 square feet of roof for the Tesla and about 185 for the truck.
One note on the truck: Ford stopped building the all-electric F-150 Lightning in December 2025. We kept it here because many people still own one or are buying one used, and it shows clearly how much a bigger vehicle changes the answer.
What can push your number up or down: charging losses
Some energy is lost between your wall and your car's battery, usually around 10%. The EPA ratings used in this guide (and in our calculator) are measured at the wall, so they already include these losses; you don't need to add anything.
If you use the efficiency shown on your car's own screen instead, it usually leaves charging losses out. In that case, add about 10%. For the Model Y in California, that would mean about 5.6 panels' worth of energy instead of 5.1, which still rounds up to 6.
Winter
In winter, days are shorter and the sun is lower, so your panels make less. At the same time, your car uses more energy because it has to heat the cabin and battery. If you want solar to cover your charging even in January, you'll need a bigger system than the yearly average suggests. Our winter guide has the full numbers.
When you charge
If your car is at home in the daytime, it can soak up solar power as it's made. If you only charge at night, your panels send power to the grid during the day and you buy it back later. Whether that's a good deal depends on your utility. Some still credit you at the full price. Others, like California under NEM 3.0, pay only a few cents. In that case, a home battery or charging at home on weekends makes a big difference.
Tax credits
The 30% federal solar tax credit (Section 25D) ended for systems installed after December 31, 2025. All the costs in this guide assume you get no federal credit. Some states and utilities still offer rebates, and you can look yours up on DSIRE (dsireusa.org). Talk to a tax professional before counting any incentive in your budget.
An example: Maria in Austin, Texas
Maria drives a 2024 Hyundai Ioniq 5 Long Range RWD, rated at 30 kWh/100 mi. Between her commute and weekend errands, she averages about 40 miles a day. That's 12 kWh of electricity a day.
At Texas's average home electricity price of about 15.9 cents per kWh, charging from the grid costs her about $1.91 a day, or about $700 a year.
Texas gets around 5.22 peak sun hours, so one 400 W panel makes about 1.71 kWh a day for her. Twelve divided by 1.71 is just over seven, so she rounds up to eight panels (3.2 kW).
At about $3.00 per watt installed (close to the national average reported by SolarReviews), with no federal tax credit, those eight panels cost around $9,600. If they replace the roughly $700 a year she would spend on grid power, they pay for themselves in about 14 years.
Two things can change that. Maria works from home two days a week, so on those days she can plug in at midday and use her solar directly. That's the best case. On days she charges at night, her savings depend on how her electricity plan pays for the solar she sends to the grid, and many Texas plans pay less than the full retail price. On the other hand, if Maria compares solar with the gasoline she used to buy, not with grid power, the payback is much faster.
Maria is an example, not a real customer.