Start from your yearly mileage
Most people know roughly how many miles they drive a year. So here's the simplest way to size solar for your EV: start from your yearly mileage.
For a typical electric SUV like the Tesla Model Y, in a place with average US sunshine, you'll need about 5 panels for 10,000 miles, 8 panels for 15,000 miles and 10 panels for 20,000 miles. Here's how we got there, what it costs, and how to adjust it for your own car and roof.
The quick answer
This uses the same assumptions as our calculator: a 2024 Tesla Model Y Long Range (29 kWh per 100 miles, EPA), 400-watt panels, the US average of about 4.98 peak sun hours a day with 18% system losses (about 600 kWh per panel per year), and $3.00 per watt installed. Panel counts are rounded up.
| Miles a year | Energy the car needs | 400 W panels needed | Cost, no tax credit |
|---|---|---|---|
| 10,000 | about 2,900 kWh | 5 panels (2.0 kW) | about $6,000 |
| 15,000 | about 4,350 kWh | 8 panels (3.2 kW) | about $9,600 |
| 20,000 | about 5,800 kWh | 10 panels (4.0 kW) | about $12,000 |
What these costs include
These costs are what you'd actually pay. The 30% federal solar tax credit (Section 25D) ended for home systems installed after December 31, 2025, so there's no federal discount to subtract anymore. Some states and utilities still offer rebates; check DSIRE (dsireusa.org) for yours.
Our $3.00 per watt is a slightly cautious national average: SolarReviews puts the 2026 average at about $3.03 per watt, and EnergySage at about $2.60. Small systems often cost more per watt.
How the math works
It only takes three steps, so you can do it for your own car:
1. Work out your car's yearly energy. Multiply your yearly miles by your car's rating in kWh per 100 miles, then divide by 100. A Model Y driving 10,000 miles uses about 10,000 × 29 ÷ 100 = 2,900 kWh a year.
2. Work out what one panel makes in a year. A 400 W panel with 4.98 peak sun hours and 18% losses makes about 0.4 × 4.98 × 0.82 × 365 = about 600 kWh a year.
3. Divide and round up. 2,900 ÷ 596 = 4.9, so you need 5 panels.
You'll find your car's official rating on fueleconomy.gov. Our calculator does all of this for you, using your own state's sunshine.
Your car changes the answer more than anything
Here's the same mileage for four different EVs, with the same assumptions as above. Efficiency figures are EPA ratings for the versions listed; yours may differ.
| Car (EPA energy use) | 10,000 mi | 15,000 mi | 20,000 mi | vs Model Y |
|---|---|---|---|---|
| Tesla Model 3 Long Range (26 kWh/100 mi) | 5 panels | 7 panels | 9 panels | a bit fewer |
| Tesla Model Y Long Range (29 kWh/100 mi) | 5 panels | 8 panels | 10 panels | baseline |
| Hyundai Ioniq 5 Long Range RWD (30 kWh/100 mi) | 6 panels | 8 panels | 11 panels | about the same |
| Ford F-150 Lightning ER (48 kWh/100 mi) | 9 panels | 13 panels | 17 panels | about 1.7 times as many |
What the numbers mean
Efficient cars like the Model 3, Model Y and Ioniq 5 land close together. A big electric truck is a different story. At about 48 kWh per 100 miles, the F-150 Lightning needs about 1.7 times as many panels to cover the same miles. Ford stopped building the electric Lightning in December 2025, but many are still on the road.
Other things that change your panel count
How much sun you get: our numbers assume the US average of about 4.98 peak sun hours a day. In a cloudier state like Washington (about 3.95 hours), you'd need roughly 25% more panels. In a very sunny state like Arizona (about 6.5 hours), you'd need about 25% fewer. Shade from trees or nearby buildings also cuts output, so a sunny, unshaded roof matters a lot.
Lots of fast highway driving: EVs are most efficient in town, where they get energy back when braking. Long stretches at 75–80 mph use noticeably more energy per mile than the EPA rating suggests. If most of your miles are fast highway miles, adding 10% to 20% to your system is a sensible cushion.
Panels slowly lose power: solar panels lose a little output each year. NREL research found a median of about 0.5% per year, a bit more in hot climates. Over 20 years, that adds up to roughly 10%. If you want your system to cover your driving for the long haul, add one extra panel at the start.
When you charge: these numbers tell you how much solar you need to make as much energy as your car uses over a year. Whether that actually zeroes out your charging bill depends on how your utility credits the solar you export, and when you plug in. See our guides on net metering and day vs. night charging.
An example: Jason in Georgia
Jason is a regional sales manager in Georgia who drives about 20,000 miles a year visiting clients in a 2024 Hyundai Ioniq 5 (30 kWh per 100 miles). That's about 6,000 kWh a year.
Using our calculator with Georgia's sunshine (about 5.17 peak sun hours), he worked out he'd need about 10 panels (4.0 kW) to cover his driving. At $3.00 per watt with no tax credit, that's about $12,000.
Here's where Jason had to be honest with himself. Switching from his gas sedan to the EV was already saving him a lot: at about 32 MPG and Georgia's gas price, he used to spend about $2,400 a year on gas. But that saving came from the EV, not the solar. The solar only replaces the electricity he'd otherwise buy from the grid. At Georgia's average price of about 16 cents per kWh, that's about $960 a year, so the panels take roughly 12 to 13 years to pay for themselves.
That's still within the 20 to 25 years most panels are warrantied for. But it's not the five-year payback a salesperson might suggest by comparing solar with gasoline. Jason went ahead because he planned to stay in his home long-term and liked locking in his "fuel" cost.
(Jason is an example, not a real customer. His real savings also depend on how Georgia Power credits the solar he exports.)