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The Prius Prime solar panel roof I think can net 3-6 miles a day under ideal conditions (which we're probably close to here in Arizona). I think that's a littl

The Prius Prime solar panel roof I think can net 3-6 miles a day under ideal conditions (which we're probably close to here in Arizona). I think that's a little more than people would expect, but still only applicable in niche conditions (tiny daily commute, or a longer non-daily commute). I think the math works out to ~4-6 years to break even for the cost of adding the solar roof assuming $0.15 per kwh, which isn't terrible. If solar tech gets more efficient or cheaper, I think it starts becoming a much more attractive option in some areas. If you get into the 10+ miles per day range, that would cover a lot of peoples commutes in certain areas.

jeffbee 1y ago
The Prius Prime solar roof is a $610 option available only on the top XSE trim level, so a hypothetical buyer is paying ~$7500 to access this effectively negligible amount of energy. ETA: and the fact that this option is tied to the significantly less efficient 19" wheel package, instead of the standard 17" wheels, means that this will never, ever be a net benefit.
- mattmaroon 1y ago
  Not if they were getting that trim level anyway.
beAbU 1y ago
Does the extra 3-6 miles factor in the need to now run the AC much more aggressively because the car will be hot from sitting in the sun all day? If this quoted number comes from the manufacturer itself, then I think the answer is "no".
- kgermino 1y ago
  I don’t think you’d have to run the AC any more aggressively with the solar panels than with a traditional steel roof? If you’re suggesting it wouldn’t work in a garage, that’s obviously true (and another factor in whether car solar makes sense) but many (most?) people park their cars outside during the day anyway. I for one can’t remember the last time I parked under cover
- danans 1y ago
  > Does the extra 3-6 miles factor in the need to now run the AC much more aggressively because the car will be hot from sitting in the sun all day? Most cars are already sitting in the sun all day.
  - aziaziazi 1y ago
    Not here in European cities where they’re either within a multi story park or in the side of a half day shaded tiny street.
    - parsimo2010 1y ago
      You are not getting the 3-6 mile per day boost if your car is parked in the shade.
      - tstenner 1y ago
        That's his point. You won't get any reasonable charge because you (mostly avoid parking your car in direct sunlight
    - sdenton4 1y ago
      Yah, it's a great point that the whole scheme is predicated on very questionable land use policy...
    - gambiting 1y ago
      What kind of European cities are you talking about lol, no offence but I hate this generalisation of "European" anything as if Southern Spain has the same culture and architecture as Poland or Lithuania.
      - gunalx 1y ago
        It is a somewhat fair generalisation of urban europe to have more innside parking or tall ish buildings that give shade.
- thinkalone 1y ago
  The initial use of solar on the Prius was to power a ventilation fan while the car was parked, and the current version seems to specifically be designed to provide power to the air conditioner while driving. But, I also can't imagine the difference between cooling down the cabin is much different from parking in the sun or in the shade - you'd be running it continually to achieve "room temperature" during the entire drive either way.
  - saltcured 1y ago
    You can't imagine that air conditioning power draw varies with the heat load that it is working against? As a heat-pump, it takes more energy to move more energy. In the old days, they used duty cycle to adapt to the changing load. Modern ones do things like varying compressor displacement or compressor speed to adapt to the load. Variable frequency inverters are used to efficiently drive electric compressors. The variable displacement trick is used in ones mechanically linked to internal combustion engines. It can vary the compression stroke to account for different load as well as different engine speed.
    - geerlingguy 1y ago
      Watching power draw on my Leaf with LeafSpy, the AC seems to use between 500-1000W (maybe more sometimes, but that's just off the top of my head from a few times running it while driving). At the low end maybe achievable with a full rooftop covered in solar panels, but probably not adequate at 1kW+.
- lupusreal 1y ago
  To my thinking, the best use of a solar panel on a car is running a low power AC unit all the time whenever the car is in the sun. Parking in the shade often isn't possible.
singpolyma3 1y ago
That's still 3-6 fewer miles worth of charging to do from more expensive sources. Even if it can't come close to covering your full use it's still covering something
- IAmBroom 1y ago
  Not if it won't recover it's own costs.
  - cma 1y ago
    It may still lose on this, but you would also want to include the externality costs that the consumer doesn't themselves bear for whether it is worth it overall.
  - dzhiurgis 1y ago
    Cost is convenience. Manufacturing cost is like $40 cells, $20 electronics and $200 in glass fusion, mounting, etc. My car eats 200W just being online so it would be useless to charge from solar.
thegrim33 1y ago
13.6 kWh battery. 39mile EPA range. Equals 2.87 miles of range per kWh. Leaving it out for 8 hours straight, on a sunny day, in LA, netted 915 Wh. Or, 2.86 miles. [0] Not 3-6, 2.86. 2.86 miles of charge, but only if left outside, uncovered, in full sun, on a fully sunny day, for a full 8 hours, in a place that gets effectively the maximum amount of solar radiation per day out of anywhere in the entire country. Now, do the same experiment anywhere else in the country, that doesn't get max solar radiation, or that can't get full sunlight for full 8 hours, or where it's cloudy at all, or rainy at all. 2.86 miles per day is the practical MAXIMUM, given perfect conditions. For the average scenario it'd be some fraction of that. The 6 miles figure is what they said you'd get if, in addition to perfect conditions, "if the sun shifted its orbit" (?) and gave perfect sunlight for 12 hours straight. Which is a number which should obviously not be thrown around as if it's obtainable. The fact that they're quoting numbers about what range you'd get if the solar system was constructed differently also makes me doubt the impartiality of their experiment and the numbers they provided. [0] https://www.motortrend.com/features/the-2023-toyota-prius-primes-battery-could-take-three-weeks-to-recharge https://www.motortrend.com/features/the-2023-toyota-prius-pr...
- conjecTech 1y ago
  EPA range tends to be pessimistic for EVs as it assumes you are always traveling at highway speeds. Even small reductions in speeds can make EVs much more efficient since drag is quadratic. A quick google search shows Prius prime owners reporting 4-5.5 miles/kwh, so the 3-6 mile range is entirely plausible.
  - slaw 1y ago
    EPA's city cycle speed is an average 19.6 mph, highway speed is an average of 48.3 mph. City range weighted at 55% and the highway range at 45%.
    - bangaladore 1y ago
      I don't think it's that simple. IIRC you don't have to do the city testing. https://www.epa.gov/greenvehicles/fuel-economy-and-ev-range-testing https://www.epa.gov/greenvehicles/fuel-economy-and-ev-range-...
roamerz 1y ago
There is going to be a parasitic drag loss to figure into it as well. I think the only way to accurately calculate that would be in a wind tunnel or maybe an amp meter with a before and after installation under identical conditions.

jeffbee 1y ago

The Prius Prime solar roof is a $610 option available only on the top XSE trim level, so a hypothetical buyer is paying ~$7500 to access this effectively negligible amount of energy. ETA: and the fact that this option is tied to the significantly less efficient 19" wheel package, instead of the standard 17" wheels, means that this will never, ever be a net benefit.

mattmaroon 1y ago
Not if they were getting that trim level anyway.

beAbU 1y ago

Does the extra 3-6 miles factor in the need to now run the AC much more aggressively because the car will be hot from sitting in the sun all day? If this quoted number comes from the manufacturer itself, then I think the answer is "no".

kgermino 1y ago
I don’t think you’d have to run the AC any more aggressively with the solar panels than with a traditional steel roof? If you’re suggesting it wouldn’t work in a garage, that’s obviously true (and another factor in whether car solar makes sense) but many (most?) people park their cars outside during the day anyway. I for one can’t remember the last time I parked under cover
danans 1y ago
> Does the extra 3-6 miles factor in the need to now run the AC much more aggressively because the car will be hot from sitting in the sun all day? Most cars are already sitting in the sun all day.
- aziaziazi 1y ago
  Not here in European cities where they’re either within a multi story park or in the side of a half day shaded tiny street.
  - parsimo2010 1y ago
    You are not getting the 3-6 mile per day boost if your car is parked in the shade.
    - tstenner 1y ago
      That's his point. You won't get any reasonable charge because you (mostly avoid parking your car in direct sunlight
  - sdenton4 1y ago
    Yah, it's a great point that the whole scheme is predicated on very questionable land use policy...
  - gambiting 1y ago
    What kind of European cities are you talking about lol, no offence but I hate this generalisation of "European" anything as if Southern Spain has the same culture and architecture as Poland or Lithuania.
    - gunalx 1y ago
      It is a somewhat fair generalisation of urban europe to have more innside parking or tall ish buildings that give shade.
thinkalone 1y ago
The initial use of solar on the Prius was to power a ventilation fan while the car was parked, and the current version seems to specifically be designed to provide power to the air conditioner while driving. But, I also can't imagine the difference between cooling down the cabin is much different from parking in the sun or in the shade - you'd be running it continually to achieve "room temperature" during the entire drive either way.
- saltcured 1y ago
  You can't imagine that air conditioning power draw varies with the heat load that it is working against? As a heat-pump, it takes more energy to move more energy. In the old days, they used duty cycle to adapt to the changing load. Modern ones do things like varying compressor displacement or compressor speed to adapt to the load. Variable frequency inverters are used to efficiently drive electric compressors. The variable displacement trick is used in ones mechanically linked to internal combustion engines. It can vary the compression stroke to account for different load as well as different engine speed.
  - geerlingguy 1y ago
    Watching power draw on my Leaf with LeafSpy, the AC seems to use between 500-1000W (maybe more sometimes, but that's just off the top of my head from a few times running it while driving). At the low end maybe achievable with a full rooftop covered in solar panels, but probably not adequate at 1kW+.
lupusreal 1y ago
To my thinking, the best use of a solar panel on a car is running a low power AC unit all the time whenever the car is in the sun. Parking in the shade often isn't possible.

singpolyma3 1y ago

That's still 3-6 fewer miles worth of charging to do from more expensive sources. Even if it can't come close to covering your full use it's still covering something

IAmBroom 1y ago
Not if it won't recover it's own costs.
- cma 1y ago
  It may still lose on this, but you would also want to include the externality costs that the consumer doesn't themselves bear for whether it is worth it overall.
- dzhiurgis 1y ago
  Cost is convenience. Manufacturing cost is like $40 cells, $20 electronics and $200 in glass fusion, mounting, etc. My car eats 200W just being online so it would be useless to charge from solar.

thegrim33 1y ago

13.6 kWh battery. 39mile EPA range. Equals 2.87 miles of range per kWh. Leaving it out for 8 hours straight, on a sunny day, in LA, netted 915 Wh. Or, 2.86 miles. [0] Not 3-6, 2.86. 2.86 miles of charge, but only if left outside, uncovered, in full sun, on a fully sunny day, for a full 8 hours, in a place that gets effectively the maximum amount of solar radiation per day out of anywhere in the entire country. Now, do the same experiment anywhere else in the country, that doesn't get max solar radiation, or that can't get full sunlight for full 8 hours, or where it's cloudy at all, or rainy at all. 2.86 miles per day is the practical MAXIMUM, given perfect conditions. For the average scenario it'd be some fraction of that. The 6 miles figure is what they said you'd get if, in addition to perfect conditions, "if the sun shifted its orbit" (?) and gave perfect sunlight for 12 hours straight. Which is a number which should obviously not be thrown around as if it's obtainable. The fact that they're quoting numbers about what range you'd get if the solar system was constructed differently also makes me doubt the impartiality of their experiment and the numbers they provided. [0] https://www.motortrend.com/features/the-2023-toyota-prius-primes-battery-could-take-three-weeks-to-recharge https://www.motortrend.com/features/the-2023-toyota-prius-pr...

conjecTech 1y ago
EPA range tends to be pessimistic for EVs as it assumes you are always traveling at highway speeds. Even small reductions in speeds can make EVs much more efficient since drag is quadratic. A quick google search shows Prius prime owners reporting 4-5.5 miles/kwh, so the 3-6 mile range is entirely plausible.
- slaw 1y ago
  EPA's city cycle speed is an average 19.6 mph, highway speed is an average of 48.3 mph. City range weighted at 55% and the highway range at 45%.
  - bangaladore 1y ago
    I don't think it's that simple. IIRC you don't have to do the city testing. https://www.epa.gov/greenvehicles/fuel-economy-and-ev-range-testing https://www.epa.gov/greenvehicles/fuel-economy-and-ev-range-...

roamerz 1y ago

There is going to be a parasitic drag loss to figure into it as well. I think the only way to accurately calculate that would be in a wind tunnel or maybe an amp meter with a before and after installation under identical conditions.