DO GEN III SOLAR PANELS HELP MPGs?

I realize this won't be the technical answer you want, but since you're unlikely to find someone with two other wise identical cars to drive to all three locals to test this for you, I'll just throw in my engineer's gut and personal experience from having the panels.

They have some minimal effect on fuel usage by reducing AC usage on hot days. But Prius AC is already very efficient, so not a big effect. They do keep the interior quite tolerable though, even on hot days, so I would say they are more than just "marketing cache".

 

Now see, having lived in both Elko NV (where it snows ten months a year) and Greenwood MS, my question would be "Does it cool the car when off as well where it is humid as it does at the same temperature when it is arid?"

Since solar only runs when the car is off, driver comfort is the only mileage effect.

 

By exhausting some unwanted heat when the car is off and keeping the interior cooler, the panel undoubtedly reduces the load on the AC somewhat, since much less
AC needs to be used to be used to bring the cabin down to a tolerable temperature. Small effect though, in the grand scheme, and I doubt you could even control the other variables in the experiment well enough to measure the effect.

 

Add weight to your car and what is the effect on fuel consumption?
Add that weight to the roof and what happens to cornering speeds and body roll?
Add both effects and you have a heavier car with more body roll so you need to go slower around corners and accelerate for longer after each corner.

It is my belief that any gains from reduced AC use are well and truly offset by the added weight on the roof. I suspect the sunroof raises fuel consumption.

 

Don't forget to check out the way cool (IMO) moon roof that comes with the solar package. It's much more versatile than the one I used to have on my Honda Accord, so I tend to use it quite a bit.

BTW, from what I've read on these forums I'm doing just fine with my MPG as compared to others. I average 48 mpg and I'm certainly not a conservative driver. When my husband drives my car he usually gets about 52 mpg, and harrasses me constantly about it.

 

Do a search, this question was beat to death 2 months ago. And to answer your question the solar roof does not very much weight to the car maybe 40-50lbs if that. So leave one 7 yr old at home and it comes out even.

Or take the hit of a couple of tenths MPG year round.

To me the bigger savings or advantage is being able to drive with the roof open and getting fresh air during the more moderate seasons without having to run the AC at all while driving. Yes the cooling while the car is closed is nice too but not as beneficial as having a moon roof to open and enjoy esthetically.

 

There are two offsetting factors in play:

1) The solar panels help reduce the interior temperature of the car, which reduces the initial load on the air conditioning.

2) The solar panels add weight and create a slightly less aerodynamic roof surface.

Both of these factors are small. No matter how you factor it, the gain or loss will be minimal. Whether you gain or lose will depend on climate and your driving profile. A Prius driven mostly at low speeds and parked in the hot sun will benefit. Drive at higher speeds in a cold climate and the panels are a complete loss.

The solar panels are mostly a gimmick. It's a fun gimmick, which I personally like, but you would have a hard time justifying them on any rational basis.

Tom

 

I actually agree with this but I love the moon roof.

 

That's okay. If we had to justify everything life would be pretty boring.

Tom

 

I always forget about the panels until i come back to my car on a particularly hot day and think, "the car is not blazingly hot...sweet!"

i haven't had great luck with MPG even driving conservatively, but i don't know to what extent the solar panel/moon roof attributes to it. I like the look, i like the functionality and think it's only a gimmick on cloudy days....

 

I'd really like one, but don't want the nav system that you have to buy to get it. By forcing this toyota has moved it from a nice to have, to a slimy sales gimmick to sell overpriced and quickly outdated nav systems.

I have to agree with the bulk of people, this should not change mpg very much, but living in a very hot place it would be nice to have a cooler car to get into. So not a gimmick, but really not a usefull package. I'd love a hybrid that plugs in and has fans in its sunroof that doesn't require needless nav packages. I'm sure the solar panels are a gimmick to distract us from the fact toyota won't sell us a plug in for a while.

 

I should probably qualify my previous response by saying I don't really think the solar panels are just a gimmick but I do think their impact is minimal, at least in my light-colored car.

This Summer I honestly couldn't tell whether the solar panel had been working until one day when I wanted to sit in my car and check e-mail before going into a business meeting. (BTW I think I read somewhere you shouldn't do this) In any case, the solar ventilation system kicked in after a couple of minutes and it did push the hot air around but it doesn't cool it so I became pretty uncomfortable and didn't sit there very long. That said, if I had it to do all over again I would still buy the solar package because, as I said before, the moonroof is awesome.

 

The solar package will have no real impact in increasing mileage in itself, it only powers fans that bring draw air out of the vehicle. If a non solar car was parked in the summer with windows down, the interior temp would be similar. So saving fuel by not running AC is not a real point. I not having solar may choose to roll down the windows and not run the AC. Compare weight of the solar package vehicle vs one without and that could have a small impact.

We are talking about vehicle that get between 48 to 62 mpg depending on many factors, mainly how you drive. Other factors are tire inflation, where you drive, are you running heat or AC or non, are Windows down or up and yes the temperature outside can effect temp of battery and effect efficiency.

How you drive and tire inflation will have the greatest impact on you getting the best possible mpg at any given time.

 

I still think the solar panels could be put to other good uses, such as warming the engine on cold days, etc, which could mean they'd be useful without a moon roof, but they'll have to be more efficient. Looks like 40% solar efficiency is happening in the lab at the moment.

 

The solar panels just don't make enough power to be useful for much, forget heating anything with them or charging anything really. You could trickle charge the 12V battery I'm sure, but that's not very useful is it?