Panasonic Pushing For Solar Roof EVs, Could Add 6 Miles Of Range Per Day

JUN 24 2017 BY MARK KANE 131

The concept of having a solar roof on an electric vehicle is pretty neat one (albeit not terribly practical), especially in an EV that, in theory ,could drive on its own.  To that end, Panasonic is pushing to make that option a more compelling value proposition – no easy task to be sure.

Still, even if the company can make the added cost reasonable, the “green cred factor” goes off the chart, so we feel many would opt for the feature.

Solar roof…not just for houses anymore?

Originally, the Toyota Prius hybrid in 2009 and Nissan LEAF in 2010 had small solar module options, but only for auxiliary/12V battery charging purposes.

In the past, placing solar modules on the roof of a car was difficult from technical point of view, as the installation was relatively expensive, and didn’t provide much power.

However technology advances, and in 2017 we welcome the first series produced car, the Toyota Prius Plug-In (aka Prime) with Panasonic’s 180 W solar array on the roof for traction battery charging. Today’s 180 W is more than three times the original 56 W unit found in Prius from 2009.

Shingo Okamoto, the general manager at Panasonic who was in charge of developing the technology said:

“Car roofs have the potential to become a new market for solar panels. We made history in the auto industry and in the solar industry with the sun powering mass-produced cars for the first time in the world.”

Six hours of full power, would give over 1 kWh of energy, which is not bad at all.

2017 Karma Revero with solar roof to charge HV batttery

We should note that there has been (and still is) another, longer running plug-in model that has an integrated solar roof powering the HV battery – the Karma Revero (formerly the Fisker Karma), which just re-started deliveries last month.   The solar roof on that car is rated at 200 W, with the company conservatively noting:

The solar roof can generate up to 1.5 miles of electric range per day, depending on weather conditions”

…so who was “first” we supposed depends on one’s definition of what constitutes “mass-production”.

The New Toyota Prius Plug-in aka Prius Prime

According to Panasonic, when using rooftop space on an EV, solar could help to cover up to about 10% of the total mileage via its own generation.

“The latest Prius is the first mass-produced model to be outfitted with solar panels that provide juice for the car’s main battery, according to Toyota. Because of seasonal variations in sunlight, the amount of charge will fluctuate, meaning the average distance traveled on a single charge will range from an average of 2.9 kilometers (1.8 miles) to 6.1 kilometers  (3.7 miles) depending on the time of year.

“That means you get about 10 percent of annual mileage from solar just by letting your car sit,” Okamoto said in an interview in Tokyo.”

Shoichi Kaneko, chief engineer for Prius noted future advancements can take the solar ‘added range’ even higher:

“We are aware that the panels are supplying only a small amount of electricity. But this system is still a breakthrough as we are making use of the energy we would be wasting otherwise. By filling all available space with cells, it is possible to extend the range easily to 10 kilometers (6.2 miles).”

Using solar roof was also considered for the Tesla Model 3, and as we know Panasonic is partnering with Tesla in batteries, solar modules and home solar roofs, so we suspect the option will be coming to future Tesla offerings at some point.

Colin McKerracher, an analyst at Bloomberg New Energy Finance said:

“You’ll see panels become more common as an option, particularly on high-end electric sedans and SUVs. But the range benefits are always going to be limited. This is mostly about feeling smug.”

source: Bloomberg

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131 Comments on "Panasonic Pushing For Solar Roof EVs, Could Add 6 Miles Of Range Per Day"

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Solar is suntimes practical! Add in some wind generation, and this story gets even better, when you start driving faster!?

That wind-thing is a joke, right?

For anyone not getting the joke: Energy can’t be created, it can just be transformed. A windmill on your car would transform your cars speed into electric energy (with losses!). When you drive fast, it isn’t wind you are feeling, it is your car moving fast through the air around it.

Yes, an old joke.

The roof area is just so small. But perhaps a big rig trailer topped with panels could help charge the Tesla Tractor trailer combo. To help charge for motive power or help with refrigeration needs.

I wonder if the Japanese are starting to just punk American consumers because they know how many stupid people live amongst us. If they just painted the roof with reflective paint, the added benefit of reduced air conditioning would far outweigh anything we can do after 2 state changes from that energy to solar to electric and back to mechanical.

On average my AC reduces range by about 3-7 miles daily. Painting reflective paint won’t erase the need for AC, but if it did it would be 3-7 miles. Then only in the extreme case would it save more, one mile. Reflective paint won’t eliminate the need for AC 100% either. Plus it would just increase heating power needed in the winter.

Already built. The InVentus Ventomobile!

A vehicle that can drive against the wind. Powered by wind energy only! Designed and built by students at the University of Stuttgart.

I love Solar, but this is pretty close to ridiculous. 6mpd! That’s not going to really change anything. First, if I’m needing charged, I’m going to have to plug in, 6 miles won’t make a difference. And if I have to plug in, then the time to add the 6 miles isn’t much, and the AC charging is going to fill it up before the solar will.
And then for those of us that park in garages, it really doesn’t help at all.

It’s definitely a Panasonic marketing gimmick. There’s no value to the end user at all. To be useful, I’d probably need to get 20 miles in about 3 hours, about 1.5 kW charging per hour.

My question to you: if a person can afford to add it and the decision isn’t made based on monetary factors, why not do it? Even if it is a few kilometers per day, it’s something that wasn’t being taken advantage of before. Outside of reasons based on cost, I don’t see why someone wouldn’t add it… Also, as costs come down, it makes more and more economic sense to add solar to car roofs.

People are idiots, but the cynical corporations that feed them misinformation and snake oil are aholes!

I don’t believe for one second that a solar panel on the roof of a car is going to deliver anywhere near six miles per day. Is it even conceivable it could do so for one car on the equator on a single day? Barely. Even expensive, high-efficiency panels would give less than 200 watts on average from a square meter. That’s if the panel is always oriented directly towards the sun. At the equator. With the car never in any shade. With no clouds during the day.

It’s simply a stupid gimmick for people who don’t like to think beyond the immediate associations set off by the words “solar panel”.

Me likey Solar, solar good.

Shiny car!


Thinking they figure the 200W panel is parked in the sun for more than an hour. Many locales could have 4-6 hours of full sun on the panel and therefore produce over 1kWh of electricity. That’s enough to go over 4 miles. Especially since the power is DC, and so does not have the burden of AC to DC conversion losses the way the energy ratings of EPA do.

And you can’t just ignore cost. One reason is enough if it’s a good one.

There are other spaces where solar panels can be more cheaply integrated and produce more energy. Even if you don’t move the panels to track the sun you can do much better than on a car roof simply by tilting the panel. The sun is directly overhead only at the equator, so having the panel horizontally is a waste of sun.

If panels become dirt cheap and we’re running low on better places to put them, by all means. But I suspect before then we’d be making more electricity than we’d know what to do with.

Every time someone buys a Model S they are ignoring costs. It is only logical to assume those same purchasers would opt in for solar roof panels.

Today if a car is left parked for an extended period of time, there is a risk that the battery will fall to very low levels (and possibly damage itself). Preventing this with a solar panel is more interesting to me than a few miles per day.

And that, in my opinion, is the only valid argument in favor of putting solar cells on the roof of a car. If someone is going to invest in solar cells, far better to put them on the roof of your house or apartment building, where they will generate energy every day.

I think it’s ridiculous to encourage people to leave their car outside baking in the sun all day, just to add a few miles to the range. Cars should be sheltered properly, as much as possible, in a garage or at least in the shade, and not left in direct sunlight.

Absolutely. Sun degradation of paintwork, seals etc will out weigh this minuscule benefit.
Although, would that output be any use in assisting the car’s aircon whilst driving?
Also this roof will be very susceptible to damage both in crashes and from falling objects.
It’s a crap idea.

Do you guys even have jobs or know anyone with a job? 10s of millions of people park outside at work every day for at least 8 hours during prime solar generation periods. They are already letting their vehicle bake in the sun. Might as well put the car to work while it sits there.

Thank you – I was also wondering if I was the only one that worked for a living. My i3 is out in the parking lot right now baking in the So. Cal. sun.

If I could really get 6mi/day, 5/days per week, that would give me 30 mi/week – or 1-day free commute. Over the course of the year that would be about 40-days of free commutes (taking onto account rain [limited, but does occur]and vacation) – about 1-month of driving.

Bah! You might as well point out that a car left parked for “an extended period” might erode away! We’re not talking about geological time here… Li-ion holds its charge quite well. Losses are less than one percent per month. And that’s not percentage points either. So if you have 10% SoC now and just leave the battery alone you’ll have more than 8.8% one year later. The issue with SOME cars (Tesla anyone?) is that they don’t leave the battery alone. But vampire losses are just crappy engineering. A smartphone that’s turned on but not used can last well over a week even though it’s communicating frequently with base stations, receiving push notifications, downloading and installing updates and so on. My iPhone 6+ did, although I only discovered this when I got another phone and decided to test the standby capability on the one I no longer used. So a car could do the same. A smartphone battery is a single lithium cell with capacity typically about 3 Ah, so it stores just 3.7 V * 3 Ah = 0.0111 kWh… There’s nothing the parked car needs to do that your cellphone doesn’t. And your phone needs to do… Read more »

Adrian is right, having a solar panel on the car will prevent any vampire consumption problem when you leave your car parked for a long duration at an airport while on a foreign trip. It happend to me after 2 weeks and the car was not able to start, on a sunday at 22 h!

I just don’t understand that others don’t understand the interest of a car solar panel.

My thoughts exactly.
I remember a case where a fellow left his car at the long term parking area while he was traveling for an extended period, and when he returned, the battery was flat.

All it does is offset the vampireic drain, and doesn’t weigh too much more, I’d call it a win.

My Ford ranger gets a flat battery after about a month of non-use, and then it won’t start. Its a serious issue since we have two BEVs. The ranger is my backup car. I solved the issue with a solar panel charger, so this would seem to be an argument for putting solar roofs on all cars, including gas ones.

Not to mention that the battery on a gas car will take about 2-3 run flats before it needs replacing.

If I could park this car in a parking lot and go work for eight and half hours that would be fairly useful if I could get six miles of range considering I only live six miles from work.

Also if the car sits around almost all day in the drive way with the sun pounding down on it I would love to collect a other wise wasted resource.

Technically if the car had a 100 mile range and I had some days where I didn’t leave the house the car could in theory collect all the miles I drive on sunlight or at least 60% of them if the car ended up collecting 6 miles a day on sunlight.

If the car sits around all day in the driveway with the sun pounding down on it, you would do better to install a carport, and put solar panels on top of it. The carport cover is 100% guaranteed to sit there all day, with the sun pounding down on it. Furthermore, you can tilt the panels correctly.

Forgot to mention, the other obvious benefit of the carport approach is instead of having your car heat up, and suffer various UV-induced aging effects, it gets sheltered. Also from snow, if you live in an area with snow.

You can do both. It is not mutually exclusive. When your car is parked on the street it gets energy and your car port as well. Your car can’t always be under a car port.
Then there is another interest in car solar, it is a forcing function for ultra high efficiency panels because the surface is limited and small, so you need to look at the highest yield possible. Price is not important because it is a limited surface but increasing the yield to the max is important. Only satellites provide a similar case but that is not a mass market and the panels are under different constrains, so you really create a new specific technology development area which is always a good thing.

Well, the car port thing was specifically in response to Ocean Railroader’s hypothetical. Sure, you can always pose a hypothetical where car roof solar has some utility — the question is how narrowly you have to craft it.

If people want to buy solar panel car roofs, and manufacturers want to take their money, all good as far as I’m concerned. But I know for a fact that the value to me, based on how I use my car, would be very close to nil. I suspect this is typical of EV owners, since at present it’s not very practical to own an EV unless you have dedicated parking you can charge at, which usually means garage or driveway (see: solar car port) at home. Many of those not covered in this group will be city dwellers whose street parking is heavily shaded by tall buildings, or who park indoors (but not in dedicated parking, poor devils). I fully acknowledge you can come up with a hypothetical case where this doesn’t apply, nor can I offer a study to prove my case. But I’d bet money on it.

By all means, do buy a solar car roof and drive the market.

Per “This is mostly about feeling smug.”, actually, for myself, I disagree!

For you, and others in your situation, you are probably right, but thus would mean, on a Tesla Model 3, that I could cover my daily commute, and part of my weekend jaunts, too!

So that would mean even less need for me to plug in at home, and since I park in the Sun, anyway, might as well make it work for me!

On a good week, it could even put more charge in the car than I started the week with, after a weekend drive! – Yes, my commute is very short!

No Robert, it wouldn’t. The six miles is a fabrication and completely unrealistic unless you’re at the equator and mad enough to still wish to park the car always in the sun, never in shade or a garage. Far better to either put the panel on your house, or pay someone else (for example a utility) to put one on a patch of otherwise unused land, where the same money can buy much more panel and produce more energy per square meter of panel, and use that electricity to charge your car. It is categorically a stupid idea in every way, possibly expect as a business move. As you and several others here prove, there’s plenty of people who simply want to believe that the snake oil is a wonderful product. I think the people who take your money are unethical, but ultimately it is your unwillingness to accept that this really is just plain stupid that’s to blame. Therefore you’re also a part of the problem, and more gullible folks will be fooled to buy this senseless gimmick rather than simply but solar electricity – which will power not only their car, but their heating, warm water, appliances and… Read more »

Given the current weight and efficiency of solar cells this isnt practical for most. But it is a cool option for those who like the idea and in 5 or 6 years the cells may be light and efficient enough to make it worthwhile.

It is not the Solar Cells that weigh so much, in a typical panel, most of the weight is the Glass Face, Wires, and the Frame!

Buy some individual Solar Cells, you will see how light bare cells are!

Tesla is going Glass Roof, anyway, so might as well lighten the tint, and add cells under that glass!

It’s not a “cool option” for those that “like the idea”! It’s a stupid gimmick for people ignorant enough to advertise their own ignorance!

Tera, I want 6.6 kW charging for my Volt. I am tired of getting just 10 miles of additional AER over lunch time, then having the genset kick on just a couple miles before I get home in the evening. Do I need it? No. But it would be fun to have faster charging so the genset would stay even more of the time.

Would getting 4, 5 or maybe 6 additional miles of AER when I leave my car in a sunny spot be worthwhile? Maybe, maybe not. Depends on price and how it actually performs. But if I was coming home with the genset on for the last 2 or 3 miles nearly every day, it would definitely be worth it.

Would it pay for itself financially? Maybe, maybe not. But it would make driving more pleasant.

Would it be as useful for a BEV where you come home with plenty of AER still in the pack most days? Less so, but let the buyer be the judge of what they like in a vehicle. Who are we to judge? It is their car, not ours.

Well, it depends on the people because that is rather what I would say of putting wood or leather seats in a car. You are better off putting that in your living room than in your car, although even there I prefer modern materials instead.
What matters is giving people options according to their own desires so that they can all find their own pleasure without judgment. Making people happy by giving them choice is a great way to increase general well being.

6 miles a day is almost 2200m per year which is very significant. If the ev is povered from the grid, in my area that will mean that the solar on the car will save about $100/year in electric costs….so the big question is how much the option add-on costs? I saw a $3000 price tag for the option being tossed around on the web….if that’s the case then there is no way you can ever recover that during ownership so it will be a hard sell. It’s much cheaper to install solar on your hous and charge from there.

They pretty much admitted, that due to value added, versus cost, this is – for most, or for many, not a Positve ROI, hiwever, I have not seen many vehicles increase in value themselves, so most vehicles are Negative ROI anyway (Return On Investment).

For the most part 6-10 Km per day adds value at present for a narrow spectrum of potential EV buyers: Very Short Commutes, Condo or Apartment Living, No Home Charging Access, Full Sun Parking at Home or At Work, during the day! For the rest, it is a nice talking feature!

Probably Solar costs less $ than adding Ludicrous Mode to a Tesla! (That upgrade used to cost $10,000!)

“…I have not seen many vehicles increase in value themselves, so most vehicles are Negative ROI anyway (Return On Investment).”

I’m not a “financial guy”, but I certainly agree with those who are when they say a car is an expense, not an investment.

Unless you can invest in a limited production, collectible hypercar- & never drive it.

There is no roi on a car unless classic or limited but that’s not the point. This is an added option that is unnecessary so it has to make sense financially in order to be added in…in a logical world.

“6 miles a day is almost 2200m “

You forgot the magic marketing words “up to”. Meaning the car being parked all day in the blazing sun in the ideal direction.

Thank you for that reality check!

Rather few people live where there are nearly zero cloudy days per year, and for those who do, many are going to choose to park their car where it will be in the shade (or even under a roof) for at least part of the day.

I admit that it’s a pet peeve of mine that solar power advocates are always citing numbers as if the sun was directly overhead for 12 hours a day, and there was never any shade.

At least with a car you can move it and orient it towards the sun. Many of us with solar home systems dont have the luxury of moving away from the neighbors shade tree

I get so exasperated by folks like you. 🙂 I’m sorry, but you can’t simply take a marketing claim at face value. You have to find a critical cell somewhere in your brain and engage it before trying to work out the implications. Marketers are banking on people doing exactly what you just did: generalize the claim, as humans are prove to, and set off a chain reaction about what it means. Consider a shampoo that makes a person “up to 100% dandruff free”. What’s actually said here is “cannot remove more than 100%”. It is true of every shampoo ever made, and of every other thing that’s ever existed. It literally has zero content! So when someone says it “could” provide “up to” six miles it doesn’t tell you anything more than “can’t provide more than six”. Even in the latter form humans would tend to anchor their estimate to the stated number, but they would regard six as less than when the phrase “up to six” is used. Welcome to the world of modern marketing. A bunch of pretty much trained hypnotists are at work 40 hours a week to design the wording, imagery and so on to… Read more »

It was stated in the original post that this will not make sense financially with 6 miles. I gave them the benefit of the doubt because I don’t care about conspiracies. When you see the detailed numbers posted by the manufacturer then we can talk about what really is there until then we can imagine what could be there. Don’t confuse critical thinking with lack of vision.

How about a “solar panel” that blocks the windows when the car is parked. That would save more energy via less ac on startup than a real solar panel roof. Maybe combine that with insulating the body for winter heater savings.

No, instead of that go with solar glass on all windows….look it up. We could have all the windows and roof and even the hood and trunk of the car covered with different types of solar cells.

Yes, going global with glass and metal surfaces will probably increase the 6 miles further. Global photovoltaic cover could be a color choice like any other. It would not be stranger than matte black or chromium and would generate more. Straubel is a former Solar Challenge participant, so he knows about photovoltaic body already. With completely black photovoltaics perhaps it would not even be noticed just like Tesla solar tiles.

I think it is cool. It is pointless, but still cool. And 6 miles per day could equal a lot more than 10% for some people. I drive less than 6 miles per day which means my car could be almost entirely solar powered.

Perhaps a solar roof on a PHEV would make sense… Just saying…

ROFLCOPTER!! See, I see what you did there!

“Nissan LEAF with small solar module for boasting its 12V battery”
Yes, it boasts that it still needs a 12v battery. Think that should be “boost”.
Can’t wait until they get rid of the 12v battery. I got fricken 24kWh battery just sitting there 80%, or more of the time, why the hell should I need a 12v battery? The cost to put the charging equipment should be well and truly offset by the cost to convert some of the drive battery to 12V. It’s not like I need to crank an engine anymore, while is really why the 12v is there in the first place.

Thanks Jason, fixed. First mainstream 12V-less EV is likely from Tesla in late 2019 (its actually a fairly complicated ask past just the removal of the 12V battery itself)…so they are coming. Scale makes all things possible (and practical).

I thought the Hyundai Ioniq ditched the 12V battery already?

Heeh, your technically/kinda right…hard call. Guess it depends on one’s definition in the case of the Ioniqs. The Ioniqs (hybrid/BEV/PHEV) have a separate lithium starter module contained inside the full HV pack. Although, I’m not sure if one really considers that a removal of the 12V…it is I suppose if you consider the absence of the classic 12V lead acid type under the hood. There still is two packs, and they have functionally separate circuits inside the larger pack, with components still run off the smaller 12V lithium battery independent of the main pack. If something goes awry, there is actually a “12V battery reset” button on the side/lower dash (weirdest thing ever imo), that “jumps” the secondary battery from the HV pack in case of failure (in lieu of the old school save)…but the car/alternator (hybrid/phev) is still charging that 12V battery while in operation as per the norm. The thinking is the lithium battery inside the pack is “nails” so it won’t ever have to be replaced/doesn’t have to be an auxiliary thing….and because it is not a separate lead acid unit, it also saves a couple dozen pounds/is cheaper to integrate into the cars. As it is… Read more »

Not specific to any EV, but since EV’s have no Engine Diven Alternator, they use a DC-DC Converter, to supply power from the main battery, to the 12V ‘Accessory’ system, for Cabin Lights, Heater/Air Conditioning Fan, Wipers, Brake Lights, Headlights, Turn Signals, Clearance/Marker Lights, battery charging/maintaining, etc. If the main battery is dead, you can still power the 4-Way/Emergency Flashers for some time on that Lead Acid Battery! And, charge your phone from an accessory socket, too!

I just wish they would make that 12V lump out of a Li-Ion package instead! Nissan and others have said, it is more usable in very low temps, easier to get a replacement if needed, and a few other, technical and inventory excuses (Explanations?)

Yes good point, I should have noted the alternator 12V charging is specific to the hybrid/PHEV. Will add a bit in a about that.

Lithium packs are not more usable at very low temps than lead-acid packs. Below around 0C the lead-acid is the clear winner on retained functional capacity percentage.

Even if lead-acid batteries have larger capacity ratings below 0 F. that should not deter a company from replacing them with something less toxic in a pure electric car. Large amounts of electricity are required to crank a cold piston engine. An electric car does not have a large, frozen engine to turn over. A well-designed lithium battery should suffice for all pure electric vehicles.

Excellent reply, thx for that.

> there is actually a “12V battery reset” button on the side/lower dash (weirdest thing ever imo)

The number one reason for needing roadside assistance is a dead 12V battery (in all cars, even ICE where so much else can go wrong!) and this simple fix means significantly fewer Ioniqs will ever need it. Everyone will follow suit.

If you must know, the 12v battery is there to close the contactors for the HV traction battery. The Leaf has a 100 amp 12v (14.1) output from its HV dc to 12vdc convertor. But first you must close the hv contactors with 12vdc so the 400vdc can flow to the dc to dc convertor and motor controller ( AC invertor). It does not have to be a crappy lead acid battery, it could easily be a lithium battery the size if a motorcycle battery. The lead acid battery was chosen to save money and its one of the few things that go wrong with a Leaf unfortunately.

Yeah. It’s really annoying that lead us still allowed, because hardly anything else is as insanely toxic even in miniscule quantities and it really is utterly unnecessary. But competent government isn’t exactly on the rise at the moment.

I honestly would want the hood and the truck of the car along with the side doors covered in panels due to my inner cheapskate not wanting that sun power to go to waste.

If there was a way to get ten miles a day from solar it would wreak gas cars. Or I could own a 200 mile range EV and then top it off at the dealership every few weeks and I won’t need to wire in a home charging station.

And, if your ’10 miles of range by Solar Power Alone’ EV, was a Tesla, you can charge from more sources than any other when you need to! So you could charge when you go grocery shopping, to a Movie, at the Mall, etc.

I’m so surprised that nobody here in the comments has mentioned this yet, but the Sion Solar Car by Sono Motors of Munich Germany is coming next year and boasts 18 miles of range from the 1,144 watts of solar cells on the whole body of the car.
Grand reveal of the prototype car that was made this spring is going to be on July 27th in Munich.

Btw, it’s an all electric car with a 30 kWh battery that’ll be priced around $23k USD (€16k plus the battery)

If you covered your whole roof you could maybe get 6 miles a day.

Still dumb. Put your panels somewhere where they will be consistently exposed and better angled. Like a roof.

How would a Condo dweller put Solar Panels on his or hers 1.5% of the roof they pay maintenance for (Remember, Elon Mentioned we build Accommodation up in 3 dimensions, but build roads in mostly 2 dimensions); also, Apartment Dwellers need every bit of help they can get, not everone works a day shift (I usually Work Midnight shift, myself!), and not every workplace has got their act together for workplace charging, even just some of their on site parking!

Obviously renters can’t usually install their own rooftop solar power, but we can hope that it soon will become commonplace for apartment buildings owners to participate in offsite shared solar projects (see link below).

Also, solar panels can be installed on any flat surface that gets plenty of sun; it doesn’t have to be the roof of a building.

There could be a double advantage to putting a roof or canopy over apartment parking stalls; keep the sun/rain/snow off your car and provide a place to install solar panels.

I live in a condo building that was built in the 1970’s and our management has been trying for years to find someone who can install a solar array on the roof of our condo. It is 8 stories up so no blockage of the light, but the vents in each kitchen and bathroom go straight up and out. That means that every solar company has taken one look at our roof and told us they can’t do it.
It is a pity, our buildings primary orientation is southern so the roof area would be perfect but the vents have, so far, caused every solar company to tell us they can’t do it.

Only Elon musk has real powerful visions it seams! “Up to 10% of the driving distance”? Come on. Dream a little higher!

Average solar irradiation is around 1500kWh/m^2 on average in the world. Say they can cover 2m(width)*1,5m(length) = 3m^2 of solar at 20% efficiency for the system that would result in 900kWh/year. If the car uses 1,2kwh/10km (hyundai ioniq) the car can go 7500km/year from electricity only, 20km/day. In Sweden average driving of a car power year is 12000km so the solar could produce more than half of the electricity needed. Add solar on the hood and trunk and the car is almost selfsustainable!!!


Your numbers are wildly off. Solar power at maximum normal at sea level is about 1000 W/m^2 (about 1350 before atmospheric absorption which you neglected). Normal means mid-day peak. As the sun hits the panel at an angle, you get less power. Average power depends on your latitude, but it’s roughly 70% of daylight hours, about 700 W on average. Daylight varies, but assume about 10 hours. Roof on cars more like 1 m^2. If you also use the hood and trunk, it might be 2 m^2. For covering the entire top of a van or Tesla, it might approach 3 m^2, but that’s not typical. 750 W for 10 hours at 20% cell efficiency, = 1.5 kWh/day. SparkEV at 24 MPH of 7.3 mi/kWh would be good for about 11 miles. At 5.3 mi/kWh my 20K miles average efficiency (and 85% charging efficiency), it would be 6.8 miles per day. That sounds great, except you don’t always park at optimal solar spot. Sometimes (or often times), you park in under shade, garage, or shadow from the buildings block the sun. It might be half the time (or less) that you park under ideal solar case, which is good for… Read more »

The only thing that differs here is the roof area and that you make it difficult for yourself and more inaccurate by estimating hours of sun and using power in watts. I went directly to kwh/yr.

As i said I’m dreaming big here. Take a look at the volvo xc90 for example. Put solar on that!

Thank you for your comments, and quick back-of-the-envelope calculations! Good stuff!

The Ioniq EV is rated at 1.7kWh per 10km. You didn’t scale down for conversion losses. And who has a roof that large?

Finally, Sweden doesn’t get an average amount of insolation. Especially on a flat horizontal surface.

I have driven the ioniq a lot. It can easily go down to 1.2kwh/10km. The epa range that is easily beaten is at 124 miles which at a energy use of 27kwh on a full charge corresponds to 1.36kwh/10km.

As i said I’m dreaming big here. The pvs are almost at 25 percent today, after some conversion losses 20 percent seems fair.

In Sweden average is about 1100kwh/m^2/year yes but on average where people are living i think 1500 is low, more like 2000 is probably more close to reality!

“Average solar irradiation is around 1500kWh/m^2 on average in the world.”

For real-world solar power purposes, your figure is off by more than three orders of magnitude. Congratulations; it’s hard to get a number that wrong! 😉

You would be well advised to learn something about a subject before posting about it, especially if it’s a technical subject like solar power. For example, did you possibly confuse kW (power) with kWh (energy)?

Here’s what someone who actually knows what he’s talking about on the subject has to say:

A typical location within the U.S. gets an annual average of 5 full-sun-equivalent hours per day. This means that the 1000 W/m² solar flux reaching the ground when the sun is straight overhead is effectively available for 5 hours each day. Each square meter of panel is therefore exposed to 5 kWh of solar energy per day. At 15% efficiency, our square meter captures and delivers 0.75 kWh of energy to the house.

That’s from a 2011 article. One written today might assume 21% efficiency, which would improve the performance to 1.05 kWh per day per m².

Full article here:

Yeah, but even that paints far too rosy a picture. On average the car-roof panel will be horizontal (it may have some tilt and/or curvy shape, but since there’s no conventional orientation of parking spaces, e.g. always on the North-South axis, it averages out as it was flat and horizontal) and therefore not ideally positioned anywhere except the equator at noon.

Real people also sometimes park under a roof or in a garage or otherwise in the shade, especially on the equator at noon, further reducing the real output.

The question of how much energy it could harvest aside, the bigger issue is simply that less money spent would lead to more solar power bring produced, and useable by your fridge and heater and cooker and lighting and so on in addition to your car if instead the panel gets to live in a solar utility.

My parents have a parking spot at home at an angle perfectly tilted towards the south! The people that get these pvs must of course know that they have the right conditions for it. Stupid to buy it if you park inside.

1500kwh/m^2/yr is The irradiation, not what the solar cell actually produces. Check my numbers again. I have a masters within sustainable energy utilization so i do know what I’m talking about.

The calculation you’re talking about says 5kwh/day right? That’s around 1800kwh/m^2/year. Pretty close to my 1500… stop being a wise ass.

how about the tesla semi? thats alot of realestate! most trailers are 53 feet long and 102 inches wide. not all trucks change trailers every stop

We are told by someone actually in the industry that trucking fleets typically have 5-7 trailers per tractor.

So whatever the cost, multiply it by 5-7 to get the amount of investment a trucking company would need to provide its BEV semi tractors with solar power from the trailer.

Probably not gonna happen. Semi trailers are built to be cheap and interchangeable. Putting solar panels on the top of some would largely eliminate that advantage.

The “amount of energy harvested” perspective improved a lot in this case, because many more trailers than tractors implies the trailers are parked a much bigger part of the time than the tractors.

But it’s still stupid because a solar utility would make much better use of the panels. Unlike trailers a solar utility can be specifically located somewhere that’s really sunny and actively track the sun. It’s output can be used for a gazillion things besides driving. And we wouldn’t ask have to be blinded by the reflections from trailers covered (roof and sides) in poorly utilized solar panels!

The panel can be on the trailer but it is also conceivable to have the panel attached to the tractor but able to expand above the trailer with a special articulation included to allow turns. That would solve the one tractor many trailer problem.

Boy do I get tired of hearing “I can’t tow my boat or drive 1000 miles a day with an electric car so therefore they are useless”. I’m hearing the same thing here, “because it’s not a full charge it’s useless”. Whatever happened to “the right tool for the job”? When we retire we will need our Leaf to take us to the store every day. Two miles round trip. For SOME people this could be useful. Still a lot of ICE mentality around.

Your Grocer must love you! Mine usually only sees me on the Weekend!

However, my daily Work Commute could be less than yours, but at present, I typically do a few other things on the way home that add an extra 3-4 blocks to the drive, so, yes, this 6-10 Kms per day in the Summer, would mean little need for me to plug in, even on 120V, to top up, until Winter comes, or I head out on my usual multi-day Road Trips!

The issue here is that if you’re going to put a solar cell somewhere, you should put it somewhere where it will be more effective.

Solar cells aren’t free. Why spend the money to put one where it won’t get consistent sun when I can put it in a place where it will?

What happens when I park in a parking garage? Or my home garage? Or what happens when parking lots around me put up solar trees covering the spots to harvest the sun (as they are doing)?

Just put the panel where it can be more effective and then put it in your car with a cord.

^^ This.

It’s not about whether or not solar cells on the roof of a vehicle might possibly do some good at certain times. It’s about where resources are best spent.

Well, we do have solar on our home. And we buy fresh local from the butcher every day, we are not the weekly Costco trip household. When we lived in the center of the city and parked on the street, sometimes we didn’t drive for days, a small amount of charge everyday would have been useful. I pick a car for my specific use, just like people that buy a huge truck for some specific heavy duty weekend use. It’s all about the right tool for the job.

A solar roof would be good for Auxiliary Power Units for police cars, work trucks, and tailgate parties (when you want to run the stereo for hours). Add solar to the trunk, hood/frunk for even more power. Replace the rear window with a see-through panel, too. While you’re at it, figure out a way to make the windshield solar, too.

If a guy can figure out how to land a rocket on its feet, this should be a piece of cake.

After tire-pressure-gate forced manufacturers to include TPMS in every car to boost efficiency by 2-3 percent, why not add solar PV?

The primary use I see for a solar roof is to run the air conditioner once an hour or so to keep the battery pack cool in hundred+ degree heat. That would extend battery life by years.

It could also heat the battery on sub-freezing days, or circulate air to keep cabin temperature from getting too hot. All the stuff you couldn’t afford to use battery power for over multiple days.

Only when there is no better use for power would you charge the batteries.

It’s not a good match for heating your pack. It’s not enough energy even in summer. And your pack would need heating in winter when the days are short.

If the entire roof of your car can produce 6 miles (1.5kWh) in summer it’ll produce 750Wh in the winter. Applied over a night (8 hours) to heat the pack that’s only 90W available. Tesla warns they can need more than 1.2kW to heat your pack at night in the winter.

You could use this to circulate air to keep the cabin cooler in summer. But then again you can just use power in the pack to do that. And in fact Tesla does.

Maybe Elon could have Tesla & Panasonic work on making a complete Solar Car Port to simply drop into a standard Parking Space: Voila! Instant Solar ‘Garage’ for Apartment& Condo dwellers!

The thing is that all BEV car use energy even when not used.
1 kW per 24 hours could make up for that loss.
Standing at airport for some weeks and not plugged in you would be happy to have a solarroof.

This is a much bigger problem on gas cars. They also run down when you park them and they have much less battery capacity.

Shouldn’t those be the first to get solar roofs?

Wouldn’t it defeat the object somewhat if you parked the car in the sun for hours in order to regain a small amount of energy only to have to use the air con in order to cool the car down before you can drive off ? Even if it regained some whilst driving or it was not a sunny day it still wouldn’t be practical.

Whilst I appreciate the concept, the practicality & expense of this has always made this a non starter. They would be better off improving battery tech and other areas of a car’s electrical energy use than this.

Musk estimated 2-4% of the car’s yearly power from a solar roof on the Tesla. Using Tesla solar glass would be the way to go and get the maximum area. It also fixes the problem with Tesla’s glass roofs of heating up and having to waste range energy cooling the car off. So the solar roof, being opaque gives and every greater energy boost considering it cuts energy use by the car while supplying energy to the car.

If we said we could cut green house gases by 2-4% that would be huge, that’s why it is huge on the EV’s.

Park it in the sun all day. Have the internal cooling system come on so that the battery doesn’t over heat. Probably net loss of KWh on your EV battery.

If guess that’s why they call it a sun roof.

But if you are parking it in the sun all day because you have to at home and/or work, it will be able to generate enough power to cool the internal system (or heat it in winter) without reducing the batter range.

SolarWindow™ modules are created by applying ultra-thin layers of liquid coatings on to glass, flexible plastics, all surfaces. These liquid coatings produce ultra-small solar cells and form groups called ‘arrays’. Because of the family of materials we use and the way in which we architect our design, the final product is generically referred to as a all ‘surface photovoltaic solar array’ (SPV).


As increasing range, this does not make sense, but you could almost reduce the vampire draining of the car it is about 1-2 kWh a day

Cars are usually standing more around than driving. Actually I’m always trying to park my car in a way that the sun doesn’t reach it as good as possible because it heats up the car very much. Of course, that’s the worst case for a solar roof, also because trees and their “residents” (birds, vine fretters(?), …) are tending to make cars quite dirty.

So with a solar roof you have two choices:
– In the sun: Car becomes more hot = more energy needed for cooling.
– Outside the sun: Solar roof makes much less sense and becomes more dirty = less effective even when you’re in the sun again later.

Of course, while driving you’re usually in the sun. But like I said, that’s usually only a short time period per day.


No one saw the Martian movie? A solar panel like that means no more range anxiety! You can go virtually anywhere and have an emergency backup.

I really want to have a small solar panel on the car just so that the 12 Volt battery doesn’t die after a week because of the onboard telematics which suck it dry. It’s fine if you drive it every day or every other day, but when I came back after a week the 12 V battery was just 9 Volts. And then the car wouldn’t charge because it couldn’t trigger the contactor on the main pack 🙁

A small 12 Volt power supply was enough to get the the contactor to go and the 80A DC/DC took over and charged the battery. Luckily I left the car at 80% before I left so it had a few hours to charge the 12 Volt.

When[!] solar panel efficiency exceeds 90%, on-car panels MIGHT be viable… specially if they are flexible.


Regardless that it’s physically impossible, even 100% efficient panels cannot save this gimmick from the gravitation of the supermassive stupidity at its center.

It will always be much better to let the panels live in a solar utility, which unlike cars can be specially located in the sunniest places and actively track the sun as it moves across the sky. It will also be cheaper to put panels in big arrays than on cars pretty much regardless what technological miracle is invented next. And much more practical to use that electricity for other things than driving.

It’s an old idea: do something that sparks off a particular association, in this case “green”, in people’s minds, and sell it to the kind of non-thinking people who never get beyond that feeling something gives them.

You don’t like it that’s clear but that doesn’t give you the right to bar access to others. Don’t be so intolerant, at worst its a waste of money so what? Or at best it improves further and cover 30% of energy needs in 2050 models.

A scenario for the future: What if during a traffic jam on a California freeway which involves maybe a 100,000 cars or more the solar roofs on a number of vehicles prevents just six cars from running out of power to move and an entire city of cars keeps moving? I can remember reading articles about people who bought solar roof add-on kits for their Prius were able to run their air conditioning and listen to the radio without running their battery down during hour-long Los Angeles traffic backups.

Calling visionaries “stupid” repeatedly in this forum is of no value.

Lots of negativity here. What happened to the EV community? First of all, regarding the “perfect angle”, putting the panels at the optimal angle make about a 20% difference in output. That’s why people put solar panels on their roofs, even if they’re not at the optimal angle for the sun. In any case, the optimal angle changes throughout the year, so according to the most negative people on this thread, you shouldn’t even bother putting solar panels on your roof. Secondly, solar cells are very light. Even an entire solar panel with the frame and glass is fairly light. If they were as heavy as suggested here, you would need to reinforce your roof to handle the weight. You don’t. Plus, if integrated into a car roof, you don’t need the frame, and the glass would offset the weight of the sheet metal that would be up there anyways. Thirdly, six miles isn’t nothing. That’s a quarter of my daily commute. That has the same effect of increasing the efficiency of an electric car from 100MPGe to 125MPGe (or is it 133?). Certainly nobody would be complaining about that. Fourthly, this is electricity that is directly being used by… Read more »

Multiple cars covered with solar panels have made the journey across this entire country powered only by the sun. This same achievement is also duplicated regularly in Australia. Speeds of up to 50 MPH are possible. While these vehicles are not as spacious as Ford F150’s the engineering concepts are valid.

In my opinion we have to be prepared for the advent of the electric vehicle. Solar roofs on cars would appear to be better than having massive helicopters pick up stalled cars with depleted batteries from the freeway as they do now in South Korea.

Looks like things are not looking good for Panasonic….the solar pv division that is..

I should mention that the best idea is for companies and individuals to use the parking space cover for solar panels. As shown elsewhere, that is about what is needed to completely cover the needs of an EV for average commute. Here in Silicon valley that is exactly what my company, and several others do. It is also, unfortunately, illegal to do at home, since the government of the city of San Jose has its head firmly stuck up their hindquarters.

An affordable solar carport would fit us well. This latest heatwave and I have seven temp bars when I come out to the car in the morning, and I’ve certainly had a DCQC session end five minutes in because the heat just builds during the day.

I am sort of amazed to see such vicious attacks on this idea on InsideEVs.

All I really see are advantages. PV is cheaper than you think.

How many people park their cars outside all day when at work? Most. Some may actually have a commute short enough that this is all they need on a daily basis.

What’s wrong with integrating (admittedly less efficient) amorphous silicon PV into the vehicle’s coating? Ever see amorphous silicon kick out the current in pea soup fog or pouring rain? Apparently most haven’t.

What’s wrong with gaining a few miles range while traveling down the interstate on a sunny day?

I did this to a friends golf car 20 yrs. ago that was used for getting around a gated community. It was always full and ready to go..

Also attached flexible amorphous silicon to the handle of a friend’s battery-powered lawnmower. It sat outside facing south all year. Mowed the lawn for three years without ever being plugged in.

Anyone ever hear of solar race cars? Jeez Louise!

Just the opinion of another “stupid” and “ignorant” person.

Like you, I am surprised by the negative commentary of many on this thread. Did InsideEV’s suddenly morph into CarandDriver/Motortrend? Many of these comments sound like the ones made on those websites when the first hybrids and fully electric vehicles came out. I can only imagine what would have happened at Nissan, BMW or Tesla had these type of comments won the day during the decision making process around the first LEAF, i3 or Tesla Roadster? They would never have been given the green light: “The battery weighs how much?! Energy density is what?!”, “The payback period on these things is how many years?!”, “Maximum range is going to be less than 100 miles? Dude, forget it, it’ll never sell.” Also a good thing they weren’t part of the teams building the first solar panels in the late 1970s, when prices were around $80/Watt (we’re hitting $0.8/Watt, and under, today). Isn’t most engineering about incremental change? 1-2% here, 5% over there, and maybe 10% if an engineering team gets lucky, all contributing to a constant drive towards improved efficiency. Solar cell efficiency improves roughly 0.5% a year, costs drop between 5-10% a year. I wonder where this idea will be… Read more »

Thanks Pacpost!

Even if it proves to be a technologically useless idea (not), The seed that it plants in the minds of the Joe Sixpaks of the world have substantial value in changing the energy paradigm. It’s been many years since off-the-shelf technology could take humanity off of the fossil fuel teat. It’s simply political and economic will that needs to change. It’s people’s minds and not technology that needs to rapidly evolve.

The bottom line is cost for the majority of people, and we’re getting there with solar and EVs. In 8 years from now the cost decline of batteries and mass vehicle production will have impacted EVs to the point that they are cost competitive with ICE vehicles.

Check this out:

Basically now in 2017 we are at $41k, and by 2020 it will be $35k, and in 2025 twill be $30k for a new electric vehicle.

As I mentioned in a comment upstream, I’m surprised NO ONE has piped up about the worlds first production solar car!!! The Sion by Sono Motors of Munich.

Here’s the specs:
30 kWh EV with 250 km range.
Probably around 100 miles real world.
Production in 2019
Targeted price €16,000 (around $23k USD including the battery)

30 km per day gained from the solar.
7.5 sq meters of panels
A total of 349 SunPower cells are producing 1,144 watts peak at an efficiency of 22%. Modules are produced by Ertex Solartechnik GmbH.

Great write up here:

Reveal of the prototype is July 27th!!


The Sono Motors is awesome, hope they showcase it soon and become successful. Please post about it here on 2017-07-27 if the media miss it.

Will do!! More than that I’ll be sure to give Jay a heads up so that maybe there can be an article here.

Thanks for your kind words Brandon

At 6 miles / day and 300 days / year (250 work days + another 50 shopping days) leads to 1,800 miles of Solar powered electric drive. This is 15% for a person who drives 12,000 miles / year.

Awesome, other solar companies like First Solar, Canadian Solar, Jinko Solar should jump into the bandwagon.

Meet Stella-

Better is this…. an actual usable vehicle that’s going into production in 2019:

“I love Solar, but this is pretty close to ridiculous. 6mpd!”

Average miles per day per car is 32.877. 6 miles of that on free non-polluting (the reason for EV’s) power would be 18% of the car’s miles per day.

An 18% reduction in green house gas emissions is significant.

It’s odd to see people who advocate for EV’s dismiss the solar power potential in same thoughtless manner that many ICE drivers dismiss EV’s.

If this were about practicality or price nobody on earth would buy a BMW or other luxury brand. We’d all drive Toyotas. Why are posters on this forum so stuck with their heads up their arses on this issue. Don’t like the solar panel option? Don’t buy it. Nobody goes on useless rants about the impracticalities and expense of an ordinary sunroof? Why go on about some other accessory being offered?

In short, it’s basically dumb to flail against a solar roof. Go on with your lives and quit being the ‘stop liking what I don’t like’ crowd.

i would be sooo happy not to have any more phantom drain…

also imagine the winter benefits.

For the life of me I can never understand why every time an auto manufacturer showcases a new solar roof idea it’s only 100 or 200 watts??! I find this confuses the public into thinking that’s the maximum you can really fit on the roof of a car, which is obviously not true. At least put 600 or 750 watts. Give the freakin idea a living chance for pete’s sake.

Should be: “Panasonic demonstrates the complete uselessness of solar roof EVs in a single headline”

Please. The last thing we need is to make EVs even marginally more expensive. Real engineers don’t do this.