Solar roof and mpg

Discussion in 'Gen 3 Prius Main Forum' started by PriusRos, May 8, 2009.

  1. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    How much do you think the solar roof option would affect the mpg?
     
  2. HTMLSpinnr

    HTMLSpinnr Moderator
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    There was speculation that city mpg may be affected somewhat by the extra weight. Not sure on the effects on Cd due to the different shape. We know drag is increased when the roof is open.
     
  3. sluday

    sluday New Member

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    You would need the actual add on weight of the roof and cooling sytem features to be accurate. I do know that $1800 does buy many gallons of gas.;):p;)
     
  4. john1701a

    john1701a Prius Guru

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    Not having to run the A/C as much due to having a car always cool when you get in and better venting while you drive may actually make it a wash.

    The region in which you drive will obviously have a huge effect on results too. Here in Minnesota, a window is often enough. A/C does not get used anywhere near as much as for southern owners.
    .
     
  5. sluday

    sluday New Member

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    You have to remember that the cooling feature only uses outside air to push hot air out. If it is 100 degrees outside your interior will still be around 100 inside but compared to 130-150 interior temps, it is a big difference. I live in the northeast so A/C gets use about 3-4 months a year. I would rather have $1800 to put towards the remote starter which can be used year round. But if I lived in the desert or southern climates, then I would consider the solar roof.
     
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  6. john1701a

    john1701a Prius Guru

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    It rarely ever is here. Temps in the 80's is the summer norm. The comfort effect should quite obvious.
    .
     
  7. Gadgetdad

    Gadgetdad New Member

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    I live in a hot area and have owned convertibles and sun-roofs. They were rarely used when it was hot with the beating sun and 100 degrees. The A/C is a must. Most of the use for the sun-roof was to vent the parked car more securely than "cracking a window". Ideal sun-roof weather is at night (thats why they are often called 'Moonroofs'), Spring and Fall or when temps are in the 60-80 degree range.

    Lee
     
  8. royrose

    royrose Senior Member

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    Yes, during his Earth Day chat, Doug of Prius team said the sun roof adds weight which would affect mpg most during acceleration and therefore have a greater affect on those that do a lot of city driving. He did say the effect would be "small". I submitted a question asking how much weight the sun roof added but did not get an answer.

    Of course, the weight issue would be year round, while the solar feature would be used intermittently.

    Roy
     
  9. HTMLSpinnr

    HTMLSpinnr Moderator
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    Intermittent is 8+ months out of the year here in Phoenix.

    In fact, the only way you can order a Package IV in AZ is with the roof.
     
  10. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    I'm resurrecting this discussion because the topic came up twice today. My friend stopped by her local dealer to check out the 2010 Prius. She saw a black III (without SR), but when she asked about the solar roof, the salesman told her dismissively that no one has a solar roof. When she told him that she knew people on the West Coast have them, he said that even if you could get one, it SERIOUSLY reduces the fuel efficiency, thus negating the point of getting a Prius.

    I had also been calling around again checking to see if any dealers in the area have any with solar roofs that I can go look at. Of course, nobody had any, and the guy at Koons Tysons told me that Toyota made very few SRs because they had to keep the percentage low in order to keep within the EPA fuel economy ratings -- or something along those lines.

    Now of course I know that many people have solar roofs (around 25%, counting Package IIIs and IVs with solar), including people in THIS area -- I've even seen one with my own eyes -- so the first part of what the sales guy told my friend is ridiculous.

    However, now that there have been more real-life experiences, do you think that the roof has any significant effect on mpg? Have any studies been done?
     
  11. nola_Prius

    nola_Prius New Member

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    I'm waiting on my IV with solar roof and would also really like to know this.
    In my current car, I'm lucky if I average 24 MPG around the city. (considering that it's been HOT around here lately and I simply can't help but run the A/C constantly.)

    There's no way I'm gonna change my order and get a non-solar roof, but I also hope it doesn't affect fuel efficiency by more than 1 or 2 mpg at most. Hopefully it doesn't.
     
  12. TracyJ

    TracyJ Junior Member

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    boy do i agree with that.... i've had a sunroof in my cars for the past 30yrs and have wanted a prius before but never really considered it till now. even if it's a little less in the mpg arena, it's still way better than the 23 i get now and i get to see the sun, the moon and the stars.:)

    i can't wait for my IV to get here. hurray toyota, please!
     
  13. dhs

    dhs New Member

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    I do know that at Koons Arlington Toyota, they had one come in last week with the solar roof, but it was presold. I did not want the solar roof because, well, I am cheep.
     
  14. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    All current 2010-Prius-with-Solar-Roof owners: Please post your mileage statistics so far.

    The salesman was telling my friend that the roof drops the mileage by 10 mpg -- i.e., 51mpg to 41mpg! :confused: I KNOW that can't be true but I'd like some real numbers to back that up.
     
  15. wvgasguy

    wvgasguy New Member

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    No way. Maybe 10%? is what he meant? But I doubt that either, especially if the concern is simply the weight of the system.

    The responses are all over the place in this thread. Is the question on this board concerning the weight or the loss when the panel is open?

    As for the weight, this is really a pointless question. How many people carry a tote bag in their car. That probably adds as much weight as the extra fan and motor needed for the solar panels. Also what is your reference point? I weigh 260. Am I really worried about adding 5 pounds to keep my car cool? Should I (well yes) lose weight just to offset the options I want?

    I don't know how aerodynamic the sun roof is, but if there is not a lot of wind buffeting when it's open I'm guessing the loss of FE is negligible.
     
  16. rcsting

    rcsting Toyota Fanatic

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    I'm on my 4th tank with my IV Solar. The first 3 tank averages were 55.9 MPG, 55.2 MPH, 55.3 MPG. Hope this helps.
     
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  17. cmumford

    cmumford Junior Member

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    I have a IV with sunroof. My daily commute (12 mi. each way, flat ground, 50 mph max speed limit) is 51.5 mpg. I can usually get to work hitting about five red lights, but often hit more than twice that on the way home. I'd describe my commute as somewhere in between city stop & go and highway both in respect to speed and the number of stops.

    I have my sunroof open as much as possible (>50% of the time) and doubt it is a big hit on fuel economy. It's also really fun - I give it a big thumbs up! :thumb:
     
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  18. mosttoysrk

    mosttoysrk New Member

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    Black Package IV with Solar Roof. On the third tank of gas

    1st Tank.. 48 mpg
    2nd Tank..51 mpg
    3rd Tank... 3/4 full tank 50 mpg so far.

    1st Tank running the air quite a bit..
    2nd tank cooler weather sunroof open most of the time

    3rd Tank running the air 75 % of the time.

    Sunroof is fairly quiet open, very little buffeting from the wind. When the sunroof is in vent position circulation through the vent system increases a lot, indicating how tight the car is with the windows rolled up.

    We are having unusually good weather in the Pacific Northwest with mid to upper 80's the last week. The solar panel vent system working well, having a sunshield on the front windshield along with the solar vent system helps quite a bit to keep the interior cool. Without the sun shield the large front windshield acts like a greenhouse and the vent system will have a tough time keeping up with the temp build up but it definitely is better than no air flow.
     
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  19. HTMLSpinnr

    HTMLSpinnr Moderator
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    I'm in the 50's as well, however I'd encourage you to check the MPG sub-forum rather than starting yet another MPG statistics thread-derailment here. The Solar roof adds 62lbs to the car, and changes the shape of the roof slightly (no air channel dimples). Only time it would increase drag significantly would be when open.

    The reduced A/C load at startup thanks to near ambient air is good IMHO for some "cold" start MPG improvements.
     
  20. elmo2274

    elmo2274 New Member

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    Just picked up my IV with sun roof on 7/2 so I'm still working on my 1st tank but so far I'm right around the 50 MPG mark. I'm in NC and while its been in the 90's here, I love the heat and have had the sun roof open most of the time I was driving. I'll post more figures as I get them.
     
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