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Flexible Rooftop-Mounted Solar Panels for Hybrids

Solatec panels on the roof.

Solatec LLC has introduced flexible, rooftop-mounted solar panels for hybrid vehicles, starting with a kit for the 2004-2006 Toyota Prius. Panels for other hybrid models will follow.

Solatec’s photovoltaic kit adds two flexible, conformal panels that charge the hybrid automobile’s auxiliary battery through a proprietary charger/current-limiter system concealed behind interior trim panels. The self-adhesive, rooftop-mounted panels are only 0.6mm thick and cause no change in aerodynamic drag.

The solar panels augment the charging for the hybrid’s battery pack. A SolaPrius prototype averaged an overall 10% improvement in fuel economy.

The 18V panels—originally developed for solar aircraft research—output 30 watts of current.

The kits cost $2,195 and will be available nationwide through dealer franchises. Installation franchises are currently available in most areas.


Ivan Kirigin

"A SolaPrius prototype averaged an overall 10% improvement in fuel economy."


Solar in Mojave is very different than solar in MA. From the article:

"A prototype (pictured) has been operating in the Northeast for several months under mixed driving conditions. With Solatec panels installed on the roof, the prototype SolaPrius® averages 55 MPG city and 62 MPG highway - an overall 10 percent improvement over the pre-installation numbers.* All-season testing is in progress."

This means drivers in sunny areas have more to look forward to.


Very interesting.

Wonder how wll this would work with a plug in Hybrid?


Of course with the kit selling for $2195 without professional installation (i.e. assume you can do it yourself), it will take you 40 years worth of driving to reach a payback point.

Interesting...but obviously needs to get much cheaper.


Jake, I agree it needs to be cheaper.

But I also pose this question in response.

How long will it take for someones $2000 leather seats to pay them back?

And the answer is never, This is an upgrade option for someone who wants to make a statement about how we can use less foriegn oil and produce less emissions. It is definetly not currently for someone who only wants to save a little money. But... If the government added some tax incentives it would help.


How much cheaper could it be if it was a factory install option from Toyota? A few hundred maybe?


It would be interesting to calculate the saving of energy of these PV units verses the energy required to make and install them.


I don't think it is that cheap.. on the other hand, i'm just curious if that installation would void any manufacturer's warranty?

John McConnell

I strongly agree with Paul in regard to 'payback'. When someone buys $200 shoes, or extra-special car tire rims, or a fancy coat, or installs a pool in the backyard, there is never talk of 'payback'. But if someone actually wants to do something positive for the planet it somehow has have 'payback' and be worth it.

Nothing at all against you Jake, most people ask this question when it comes to energy use -- it would just be great if we got away from looking at the conservation of energy that way.


30 watts of solar power trickling into the 12v (auxiliary) battery is not going to do much of anything significant in terms of fuel consumption. The price is really high, probably due to the flexible type panels, but you can pick up normal 15 watt panels for under $150 CAD ($300 for 30 watts), plus a 12v 7-amp charge controller for another $30 and you've got the functional equivalent of this setup. Personally I think you need 200-300 watts hooked up to the traction battery to make a real difference in fuel consumption, like the earlier post on the gen 1 Prius with solar.


One must start somewhere and one must start now. While it is difficult to find many PV applications that show a reasonable payback period, we can't wait around until the perfect and cheap technology is here. The pioneers will help us reach the critical mass in technology and volume whereby PV will be economically viable. If the alternative is an unacceptable level of fossil fuel consumption, we must embark on many of these projects as a matter of faith.

We cannot be sure if a solar future is viable, but we will never know unless we start now. In any event, the payback will be greater than, say, the billions we've pissed away on the Iraq war. At least solar doesn't have a negative payback.


I like Patrick Benard's recent article in Car & Driver when he said you'll save enough money in maps and 50 cent phone calls to make back the money you spent on the $2,000 indash navigation system :P

I think it's a pretty neat idea, it would be nice to see Toyota offer some "accessories" like these for some of the ultra ______ (whatever you want to call them) who don't mind spending a little extra on things like these.


So if I could put up with an extra 2 watts I can get a $1870 rebate. Let's see, that would buy almost 900 gallons of gas these days. Well atleast some dealer can make a couple of Hummer payments with that money.


those little panels, producing just 30 watts....... causing a 10% increase in fuel economy?


John W.

Just a few observations/comments:

Konarka, and other companies who are producing the same technology (whose names elude me right now), are making flexible, ultra thin solar panels, primarily for the U.S. military at first, but also for consumer use ultimately. These companies boast much cheaper production costs (therefore cheaper consumer costs--we'll see if this actually happens) because they don't need to expend the huge amounts of energy to super heat silicone in the same way as rigid silicon cells need to be heated, as the PV cells/material with Konarka can be "painted" or applied to plastic, cloth or other flexible or solid surfaces. It probably won't be too long (a couple years?) until you can buy these types of flexible solar sheets yourself and stick them on the roof of your car/van.

You'd have to be a die-hard to want to paint the roof of your new hybrid this way, but I think I could live with the looks. It could be the new "carbon-fibre" look for exotic hybrids.

It also looks like half the roof is still not covered by solar cells in the picture: that's kind of weak considering it costs over 2 big ones! I would think in a couple years for sure you could fabricate a system something like this yourself for much cheaper.

Some people think this small wattage won't do anything, but remember the biggest fuel savings are to be had when the motor helps start the car off from a stop: once it's rolling the drain on the battery is much less of course. If this small system helps to just "top off" the battery enough to get even a few more starts from red lights, you can indeed expect to see small gains in fuel efficiency. Let's run with it!

little shop

This is almost a scam. When you press on the pedel on the Prius you are summoning up to 33,000 watts of power just for MG1. It does not always use 33,000 watts, but often 15,000. So in full sun 10 hours those panels will add 300w hours or you can run MG1 on them for about 1 min. Thats right one min power for MG1 at half load. I figured you would need a 1000w array to make much difference, and batteries to hold that charge similar to the 'edrive' system. This might give you 30 mins of electric driving .

Pricing: COMPLETE solar systems for RV's and boats run about $15 a watt, so why is this incomplete system $66 a watt?


Bah, added weight, reduced aerodynamics,.. And how much energy was expended making the panel in the first place? Did they use safe environmental practices in manufacture? Well if we're being all environmental about this might as well go all the way.

Wouldn't the whole concept be more practical if the solar panel was on the roof of your garrage to assist charging when you come home from work? Then the panel could afford to be big and cumbersome but very efficient, powerful and possibly much much cheaper?
Not to mention a static panel could be positioned to get maximum sun at various times of the day, which can't be said for the on-car one, especially if you park it under a tree or any shady spot. I don't know about you, but parking a new expensive car in full sun does not sound too appealing. Especially when you get into it at the end of the day and stew for a while until the damned aircon can cool the cabin (which by the way is a huge waste of energy)


It's a step in the right direction, but this particular kit is too expensive. Assuming, 55 vs. 50 mpg city, $2.50 per gallon of gas, and $1,000 installation cost, you would have to drive 773,000 miles to recoup the cost.

One thing, if you add larger batteries to the Prius (such as adding the plug-in option being developed by AND the unit charges the batteries while the car is parked (don't know if it does this as the company web site doesn't give much detail), the recoup mileage requirement would drop.

$2,195 plus $1,000 installation estimate = $3,195 total cost.
$3,195 / $2.50 per gallon of gas estimate = 1,278 gallons of gas equivalent
1,278 gallons of gas * 55 miles per gallon city = 70,290 more miles than at 50 MPG
70,290 miles / 5 mpg improved * 55 mpg actual = 773,190 total miles required to recoup cost


Users in more sunny areas aren't likely to see much more difference... Because it isn't charging the drive battery it is charging the 12v auxillary system... ie: the radio, vent fans, cooling fans for battery pack, cigarette lighter, etc.

But the above statement that it can't effect fuel milage is wrong. Hybrids d what many call "hidden charging" That is, they use the main generator to create electricity to charge the 12v system, this is an increased load... reducing this load gives a noticable gain.

If you don't belive that, check out some of the high-end drag cars that run with no altenator because that pulls too much HP away from the motor. (Even with 3000hp+)

This is a great idea; Many on hybrid forums have bee discussing this, and doing this mod on thier own for a long time now. It's already proven to work, the only question is whether the cost is too much :)


Adrian... the article above already stated that there is no change in aerodynamics. Additionally Solar panels and controlls aren't heavy, I doubt that the WHOLE rig is any more than 2Lbs total.

Some others who have done this mod add a 2nd 12V battery to hold the day-time charge longer; so that COULD add a good 15Lbs-30Lbs depending on batter used but isn't neccesary.


I agree, this setup is way too expensive for the nominal recoup of the investment. This is not a status item that we should just buy, as are a nice pair of shoes. And last I checked my shoes get better milege than that car anyway. afterall, we all have expenses to contend with in the rest of our lives. And those mocking us out there that we should do it for the environment, put up the money for us or shut up. I'm sure that there are other companies offering a cheaper setup that would love to help you apply thin film cells on your car, what you aren't paying of is the marketing. THis company is just an opportunist at heart. All in the name of money.

John W.

I thought I read somewhere that it takes roughly 748 watts to give the equivalent of one horsepower in an internal combustion engine. I'm not an engineer so I need to ask if I am in the ballpark? If this is so, then the 15000 watts that little shop said is often drained from the batt-pack would be around 20 horsepower's worth.

But a Prius with good hard tires, going 35 miles/hour on more or less flat ground could almost coast to where it's going once you got it rolling! (I'm exagerating a bit here, obviously). I find it hard to believe that once it's moving (flat ground assumed) it would take a continual 20 horsepower to sustain it at such low speeds. Accelerating, yes it would. But not at a steady slow speed.

I am not saying therefore this system is adequate. It's very small capacity and basically a rip off for 2200.00 dollars, but I hope no one writes off the whole idea because of this one particular system. Just phone the manufacturer and tell them to get real with the product and the price. It's still a good idea that has merit and proven (small) results.


I agree that it's too $ ... but it's not for the purpose of driving the car. the ONLY thing it dos is store power so that the AUXIALLRY electric devices can be run off solar power.

It would be the same idea as removing a car's altenator and using solar instead.

Aaron B

Ok. This would have a use as a way to keep the battery plates tickled so that they don't become sulfated. On the auxilliary battery I can see how a more effective battery would put less of a drag on the other systems trying to charge it. 2000 is way too much IMO. Go to pulse tech and see if you can find a very thin but efficient panel to replace pulsetech's panels and cut their heavier less powerful panels off.
Konarka is nice but the main reason the military is using them is because there is no difference in their panels if they have a camoflauge design or not. The efficiency on those plastic panels are way low right now. They've teamed up wtih some other Corp's with really good tech such as "quantum dot's" but right now it's very low. If you are going to go cheap and "way thin" then maybe you want to see if you can get LightFoil
although it's probably expensive right now.


Keep in mind that the Prius' alternator equivalent (DC-DC converter) can deliver 1000 watts to the 12v system, and when "on" there's probably an average of 300 watts of electric equipment in use. 30 watts of peak solar power (unlikely to deliver 30 watts very often) mitigates very little energy consumption, I seriously doubt it will be noticeable since I have seen NO drop in fuel consumption after installing two medium-size audio amplifiers with speakers and a PC with touchscreen in a Prius. Until independent study can confirm any of their claims I would remain extremely skeptical about this particular offering.

The idea has merit, the Prius I with ~300 watts of panels plugged into the HV system improved fuel consumption by .5 MPG in Canada. That seems more realistic and technically useful in terms of power offsetting anything significant.

little shop

Again, anything less then 300w is not going to be on the radar for mpg gains. Unless you are going to count .1mpg in a 50mpg car.

Putting solar systems on buildings and puting the power back into the grid for the same wattage helps the enviroment more. The panels if installed right produce more power and it does not get wasted. If this system was in the Prius there could be many times when the power is not needed so it will not be used. Panels feeding the grid will always offset something somewhere.

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