DO GEN III SOLAR PANELS HELP MPGs?

[doc3osh1]

I scanned through all the MPG threads and did not see this answered, so forgive (or redirect) me if it's been covered:

I'd like to see a somewhat complicated comparison:

Two 2010 Prius', one with the solar-panel package and one without, each driven for at least 1 full tank of gas (preferably for a few tankfulls) in three locales:

A. In Arizona/ Texas/ Nevada region: Sunny but hot enough to require Air Conditioning (which may reduce MPGs)
B. In Northeast (not that sunny but not hot either-- A.C not needed)
C. in Boulder or some similar place where it is extremely sunny but cold

Of course ideally the same drivers would drive the cars in all three places so the driving habits would stay the same, but in any event the point is to see if the Solar Panels are "worth it", and whether they are worth it for some people (some regions) but not others... I'd imagine Toyota might find this info somewhat useful, though I have no doubt their main reason for including the panels is for marketing cache.

[rachaelseven]

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".

[JimboPalmer]

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.

[rachaelseven]

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.

[doc3osh1]

So here is the related question: I have heard that most sunroofs add a couple hundred pounds to the car due to the motor (though that seems like an unnecessarily heavy motor...). Since the solar package is only on models with the sunroof, does the extra weight negatively impact MPGs? (This may seem like a "picky" question, but I'm sure some Prius buyers have debated whether to get the package with the bigger (sportier looking but higher rolling resistance) wheels, and opted for smaller wheels due to fuel economy concerns...)

[patsparks]

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.

[doc3osh1]

Originally Posted by patsparks

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.

How hard would it be to find out the weight difference between the solar package and non-solar package Prius?

[yadax3]

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.

[mindmachine]

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.

[qbee42]

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