Hyundai Put A Solar Panel On An Electric Car But It's False Green

Once again, we see great buzz around the idea of an electric car with a solar panel on it, in this case a new Hyundai Sonata (not yet available in the USA.) Sadly, it is necessary to point out the realities behind this, because it's a pretty poor idea.

Hyundai says their solar panel will provide enough electricity to power 808 miles of driving per year, or 2.2 per day -- if you leave the car out in the sun. That's not nothing, but it's close to nothing, so close as to not justify the cost. You also give up the opportunity for things like Tesla's panoramic roof or sunroofs. This low amount of energy is shown in the history of cars with solar panels. An early Prius with a solar panel only used it to power a fan to keep the car cool on hot days.  808 miles of electricity at home prices is worth about $22 or 6 cents/day.

The question of hot days is an important one. You only drive 1-2 hours/day typically. To gain this power, you must park the car in the sun. Not everybody can do that and not everybody wants to do that, for in warm places it means the car is baking, and could easily consume all the power it generated from sitting out in the sun for a short time, and sometimes more, with the extra air conditioning needed to cool the sun-baked car down. (The AC draws about 1kw and would use up a hour of solar power if it runs for 5 extra minutes.) The panels will also add a small amount of weight.

Putting solar panels on cars can actually be anti-green. That's because if you're going to spend some money on solar panels, you want to use their full potential. That means mounting them in a sunny place, tilted at an angle to best catch the sun, and most importantly, connected to the power grid. Leaving them flat can lose 30% of the energy they generate. Parking in the shade, of course, loses almost all of it.

In fact, like the older Prius, it could be the best use of the solar panel could be to keep the car cool when you're forced to park in the sun, not to have you deliberately park in the sun to charge. The reality is that a car solar panel, which has to be shaped to the car roof, protected and robust against vibration, is much more expensive than a household or grid-solar panel. If want 2 miles of extra range a day, your best bet would be to (if you could) buy a slightly bigger battery, and pay for solar power from your electric company.