Solar roof & MPG

Toyota did not retest with a moon roof (or with 17 inch tires) and no owner is likely to be involved in testing so accurate and repeatable as to measure a difference. (owners can, and have, noted differences with different tires and wheels)

So I think the answer is no one knows, and because no one knows, the difference can not be large.

 

Oskar, if you look at a side by side image of a Prius with, and without the moonroof, you will notice that the solar roof is more flat.

It's not just the added weight, but also the change in aerodynamic shape that will negatively impact fuel economy. The larger 17" wheels have also been shown to get less MPG. The MPG penalty is likely pretty low.

 

I don't know the reason for not offering solar on the 5 package, but MPG isn't the only concern. The vehicles suspension, handling, and available payload are all affected by how heavy the car is. It very well could have been a safety reason that the solar roof was omitted on the 5.

There are several reasons I am specifically avoiding the solar roof option in my search for a Prius.

• I live in Oregon, so there are about 5 days where I can actually open the roof and maintain a comfortable temperature.
• I live in Oregon, so there are only 3 months where the car gets hot by being in the sun. At home the car sits in a garage.
• The solar roof adds weight, which affects acceleration and especially cornering performance considering the weight is at the highest point.
• 1 more potential thing to go wrong.
• It costs more. Much more.
• Body rigidity is usually compromised by placing the hole in the roof.
• The roof line is not as aerodynamic as the non-solar equipped models.
• I'd be concerned about damage when strapping things to the roof.
• My general disappointment that Toyota put a solar roof on the car, allowing people to mistakenly believe it can charge the traction battery.

 

A dealer by me has a IV with the roof package on it. Last of the 2014 around. 2015s on the way soon.

 

As I could stand to lose 20lbs myself, I'm not at all concerned about the extra weight of the sunroof.
If it makes 1-2 mgp difference, I'd be shocked.

Overall, love my sunroof, and the added bonus of the cabin-cooling fans (which help with mpg in warmer weather) that come with it!

 

I liked the roof ,but couldn't see the $1500 for it.

 

I've had my used 2010 Prius w moonroof for over a month now. Here's my take...

Purchase cost:

1. The moonroof on a used car costs only a fraction over a brand new car. You can also pretend you really hate a moonroof (because of the MPG cost, more maintenance, eats head room, etc) but will consider one if the price is right. If you play your cards right, it might even give you a reason for a good discount.

2. Whatever miniscule mpg you lose is not worth the sacrifice if it really matters to you that much. I've gotten so many comments on how beautiful my car looks and i see it due mostly to the moonroof/solar panels. The dark glass top contrasting against the white color really makes it more premium.

Energy cost:

I can already say it's been more a money saver for me. Here's why..

(Disclaimer: I'm only on my 2nd tank. My 1st tank was 62mpg, my 2nd 59mpg due to colder weather).

1. On hot days when I park in the open in direct sunlight I can stay inside with only the solar powering the fans when i would have needed the ICE idling to run the AC. I know this because i often try turning it off and within a minute it becomes unbearably hot.

If i need more cooling, i slide the windows open but crack the moonroof only an inch while keeping the roof shade closed then it becomes more bearable. This way the heat escapes thru the moonroof faster without letting more heat come thru it. The solar running the fans makes enough difference i can get away with this a lot of times. I could also probably remote start the AC without the ICE idling and keep cool inside but the solar fan is doing such a good job i haven't needed to.

For the same reason after work when i 1st step in the interior needs less cooling so saves more AC use. So whatever mpg i theoretically lost due weight/aerodynamics is more than paid by the real savings of not idling the ICE for the AC.

(Note: The solar fan kicks in only after 10 minutes power off. Once it kicks in, you can feel the difference).

2. On cold days, I keep all the windows and moonroof closed but the interior slider open. The green house effect thru the moonroof keeps the interior warm enough i use the heater less. I know the difference because i use the interior shade as my temperature control. Open for more heat, close for less.

So whatever mpg i theoretically lost due weight/aerodynamics is more than paid by the real savings of not idling the ICE for heating.

.

 

Solar arrays don't need to weigh a lot. For most designs, most of the weight is in a superstructure that can support a large surface area, withstand wind and hail, and otherwise resist movement and damage from external forces. The actual photoelectric surface can be bonded to an existing roof structure without adding substantial weight to the vehicle.

 

We have a 2012 Prius IV with moonroof pkg., and then also added the factory 17" wheels. Our avg. mileage is around 45-50. Depends on who in the family drives it and how. I imagine the slight extra weights does reduce the mileage to a small extent, however the tradeoff for enjoying the roof and its cooling feature as well as the style/handling of the larger wheels/tires was well worth it for us. I think it is personal preference-some are fine with it and some would rather have the extra mpg. Personally we are very happy having both the roof and wheels, and the car has been flawless.

 

The wheel size doesn't matter as much as the rev/mile.

Bob Wilson

 

Yes, the wheel size means next to nothing for fuel economy because of the variable-speed transmission. The type of tire does have a lot to do with it due to rolling-resistance. I can attest to the handling improvement however.

 

Oskar, a little late to the parade, but: have you tried sitting in both styles, with/without moonroof. It does reduce headroom, might be a factor.

Just my 2 cents: we've had a moonroof on one vehicle over the years. Never really missed it since.

 

I may be totally off-base here, I thought BWilson was just pointing out that the tyre circumference * revolutions = distance; and that revs/mile is preferable over wheel diameter because the latter does not take tyre aspect ratios into account and the measurements themselves are nominal before mounting.

Put another way, 17 inch tyres are 17/16 greater circumference than 16 inch tyres, but the revs/mile between different 17 inch tyres can vary considerably.