Why aren’t electric vehicles using solar panels integrated into the panoramic rooftops? Wouldn’t this eliminate the need for charging stations – to be able to collect a solar charge at most hours of the day and *during* the actual act of driving?


Why aren’t electric vehicles using solar panels integrated into the panoramic rooftops? Wouldn’t this eliminate the need for charging stations – to be able to collect a solar charge at most hours of the day and *during* the actual act of driving?

In: 1963

Not enough surface area and they’re not efficient enough yet.

ELI5: Not big enough and too slow.

There’s a recent Joe Rogan Experience episode with Elon Musk and they talk about this exact concept. The only vehicle that Musk believes this could work on is a sprinter van size vehicle, think moving/delivery van. The panels would need to unfold from the roof to triple their surface area to efficiently charge the vehicle.

They don’t deliver nearly the power required. A meter squared of solar panel delivers about 1 kW under peak conditions. Let’s assume you can fit a square meter of solar panels on your car. A chevy bolt with a 66 kWh battery would take 66 hours of peak sunlight. A Tesla Model S takes 100 hours.

Meaning you’re probably losing more energy due to the added weight of the panels than you’d ever get by charging. This is why “why don’t we put solar panels on <x>” pretty much never works unless <x> is something big and static like a building.

A solar panel produces ~0.8kWh/sq m per day and the average electric car uses around 15kWh for a 100km trip. Just from this you can see the problem, there is not enough area on a car and the panels are too low power to make any meaningful effect

They exist, but not in a state where regular comsumers can buy them, check out the world solar challenge its a race for solar vehicles that crosses australia.

Very basically, the energy captured by solar panels is…not really enough for a car. Panels will often operate at poor efficiency in many driving conditions. The panels themselves will be pretty costly and it’s also very likely that having them travel consistently at high speeds would lead to wear and tear, adding to repair costs.

Unlike other sources of “free” energy a car could make use of, like that captured by regenerative breaking, the energy of the sun hitting the car is just too expensive and cumbersome to make use of.

The Hyundai Sonata hybrid (gasoline-electric hybrid, no plug) has this exact feature. With six hours of sunlight, it can generate about two extra miles of range per day.

The solar panels aren’t strong enough, and some of the electricity generated is lost immediately because the car is heavier.

I was on the R&D team for an electrical vehicle company. My task was to research and report on all the current, up & coming and future technologies for electric and alternative power vehicles. Long story short, there is really no such thing a ‘free power’. Most things ‘consume’ more power than the generate (the weight of the panels are heavy, causing more drag therefore not efficient). Regenerative breaking, so far, is the best way to create instant power, but not long term…the battery is the weak link.

Not too many people realize the enormous negative impact mining for the minerals in the batteries have on the environment. Entire eco systems (forests, mountains, animals..) are destroyed digging out the ‘rare earth minerals’. Then the chemical waste to refine the minerals dumped back into the environment is very very bad (polluting water and land). Most of these rare earth minerals are mined from 3rd world countries and China which have little regards for the environment. “Clean Energy” is really not as clean as people think.

I know solar power is becoming a big thing. However, anyone who uses small devices soon learns how anemic they are with a tiny surface available. A solar panel on a car would be adequate for maintaining a battery in a parked vehicle if the parasitic losses were not great.

Electric cars use a lot of energy compared to how much you can get out of solar panels:

A solar panel can only put out about 20 Watts of power per square foot, and that’s only in direct sunlight.

The current Tesla Model 3 has a 62,000 Watt-hour battery.

Let’s assume you could fit 65 square feet of solar panels onto the hood, roof and trunk of a Tesla Model 3.

62000 Wh ÷ (20 W/sq.ft × 65 sq.ft) ≈ 48 h

So it would take 48 hours to fully charge the car’s battery.

That doesn’t sound ***too*** bad, right? Just two days? ***Nope.*** 48 hours ***of peak sunlight.*** Most of the US only gets about 4 hours of peak sunlight per day, so it would take more than a week. Probably more like 2 weeks when you account for bad weather.

Search for Lightyear One, a car that hits the road this year. It has a roof that is full of curved solar panels. Of course it doesn’t run eternally without charging, but if it’s a sunny day and your daily commute is not too far you should be fine.

Like everyone is saying: our current solar panels are not efficient enough to really provide enough energy for our current EVs. However, if we had much smaller and lighter EVs, then we could get there. Like this:

Claims it can go 40 miles per day just on solar and without any charging.

This is possible but probably impractical.

The available footprint of a normal car is about 6m2. At the Canadian border, you’d get about 1150 kwh/ rated kw in a year.

We’re just looking at technical plausibility, so assume thin film solar sold for drone wings. It’s 30% efficient and weighs 170 g/m2. So peak power of about 1.8kw and 1 kg of added weight.

You then get about 2000 kwh across the year, or an average of 5.6 kwh or so a day.

A typical EV will use 150 wh/km. So that’s 37km per day. The average driver only goes a little further than that per day.

The issues would be now the car has to be in an unshaded spot, and might still need to be plugged in seasonally. But if high efficiency thin film solar comes down in cost, maybe?

Btw one poster is claiming gasoline pollutes less than an EV. Not even close – EVs aren’t a static technology. The emissions and energy to make a kwh of battery have gone down steeply in recent years, along with cost.


The [Aptera](https://www.youtube.com/watch?v=HNjUdTJjiNk) does this. In sunny climates it’ll charge 40+ miles/day, and it’s got a 1000 mile battery for smoothing out irregularities in usage & weather.

The model 3 has a 75KWh battery. You could maybe fit one 400w panels on a large car. The car is rated at 240 Wh/mile. So in full sun with 100% efficient, it would add 1.5 miles per hour. Just not worth the cost and components.

What’s the point of putting solar panels on something that will (in most parts of America, for example) spend the vast majority of its life parked in a sunless garage?

I would rather have the option to invest that same money into home solar charging and profit from better electricity production capacity