 Panel Decision (click to enlarge) Solar Panels NeededTo Drive On Sunshine Mark D Larsen

When chatting with people about my Tesla Model 3 and rooftop solar, they often want to know how many panels it takes to drive on sunshine. The answer, of course, depends on the energy efficiency of the electric vehicle and the average number of miles one drives per day. Beyond that, we can use fairly reasonable assumptions to estimate the answer:

• The EPA states that there are 33.7 kWh per gallon of gasoline.

• One can calculate an EV’s miles-per-kWh by dividing its MPGe by that estimate. For example, the EPA rates the “combined” fuel economy of my Tesla Model 3 Long Range RWD at 130 MPGe: 130 ÷ 33.7 = 3.86 miles-per-kWh

• Typical solar panels generate approximately 250 watts per hour.

• To account for short winter days, long summer days, clear days, rainy days, installers usually estimate an average of only 5 hours of sunshine per day.

• One panel should therefore produce about... 1.25 kWh per day. Ergo, it would generate enough electricity to drive a Tesla Model 3... 4.825 miles.

Using these assumptions, here is a table with rows for various electric vehicles and columns for the distances driven per day. The results in the intersecting cells are how many solar panels one would likely need in those instances: As you can see, to drive only 10 miles per day with the most efficient vehicle (Hyundai Ioniq EV), one would need only 2 solar panels. At the other extreme, to drive 100 miles per day with the least efficient vehicle (Audi e-Tron), one would need... 36 panels! Perhaps it would be more helpful, however, to point out that the average commute in the USA is 37 miles per day, so the yellow column (40 miles) likely answers the question for most drivers.

Of course, the above calculations are simply to “fuel” an electric vehicle. Also powering one’s home would require many more panels depending upon the average number of kWh it uses per day. Nonetheless, the same assumptions up above (250 watts per panel, 5 hours per day) can help generate those estimates.