Putting solar panels on the roof of an electric car might seem to make sense, but in reality it may not be as efficient as you’d think.

As it turns out, solar panels don’t generate power quite as quickly or easily as we might have hoped. YouTube’s The Tech of Tech put solar panels on the roof of his Tesla Model 3 to see exactly how much extra range he could get from the sun.

The system is a little janky, and the host is the first to admit it. But it does give a rough idea of how much power a Model 3’s roof could gather if it were covered in solar panels, something that Toyota has tested on the Prius Prime.

The host claims that panels are among the best on the market and although he needs some chunky equipment to trick the system into working, it could be made much smaller if it were all integrated into the car.

After about an hour and a half of charging, he gets 7 miles of extra charge. At the sun’s height, Tech of Tech’s setup manages to recharge at the same rate as a standard wall socket. Others with different setups have found that it would take as many as 10 days to fully charge a Tesla.

Also Read: YouTuber Finds Solar Panel Trailer Would Take 10 Days To Charge His Model 3

That may not sound all that impressive, but as power that’s just being generated passively, it’s pretty cool. And seven miles could easily be the difference between calling a tow truck and getting to the nearest plug.

The host points out, though, his setup costs more than several tows, so you probably aren’t going to run out to buy it any time soon. Moreover, you’re constantly being forced to contend with shade from trees and buildings and clouds. In the end, in something that uses as much power as a modern passenger car, the power might be best spent on running auxiliaries.

The host does point out, though, that in something like the Aptera 3, a three-wheel EV which looks a bit like a solar racer, it could generate as much as 40 miles a day. That could easily cover most of your daily commuting, which makes solar panels look more interesting.