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>5kWh per day at 20c/kWh A standard perfectly installed 400W solar panel gets around 1.8 kWh a day [1]. Avg US electricity costs are 16c/kWh [2]. I think you v

>5kWh per day at 20c/kWh A standard perfectly installed 400W solar panel gets around 1.8 kWh a day [1]. Avg US electricity costs are 16c/kWh [2]. I think you vastly overstated the above. So some may get better, but ~half of people will get worse. So I'd guess this is actually under $0.30/day. >1$/ day of electricity and 3600$ over 10 years. ... i.e., if you park in perfect sun all day, every day, and there's no weather or seasonal changes, i.e., this is not possible. Picking a daily perfect value and assuming that value scales to all days is not a good estimate. Maybe, if someone is quite diligent and lucky, they will get 1/2 of the perfect value over time. So I'm at $0.30 per day at best, avg maybe $0.15 per day over 10 years, i.e., under $550 for 10 years. And of course now your solar panels are slightly degreaded, slightly less power generated, and, if you're lucky, you might get another 10 years out of them (they're on a car after all). So for a price of $2000, up front, for 20 years, you get $1k return. Of course, if you invested that $2K at 5% over 20 years you have $5300. So, not even close to being a good value. [1] https://www.solar.com/learn/how-much-energy-does-a-solar-panel-produce/ https://www.solar.com/learn/how-much-energy-does-a-solar-pan... [2] https://www.bls.gov/regions/midwest/data/averageenergyprices_selectedareas_table.htm https://www.bls.gov/regions/midwest/data/averageenergyprices...

Retric 4y ago
Justify why you think you can only stick a single 400W panel on a car. Cars are large 3D objects, you aren’t going to get nearly as much power from side panels or the dashboard as the roof, but solar panels are cheap. Also, Mount Signal Solar had a 29.7%(average 2015–2017) capacity factor from it’s solar panels. That’s averaging 2.85kWh per day across multiple years from a single 400W panel. https://en.wikipedia.org/wiki/Mount_Signal_Solar https://en.wikipedia.org/wiki/Mount_Signal_Solar Obviously most cars would never approach that but buyers are going to self select for better areas. How effective this would be in Alaska is irrelevant if nobody buys it in Alaska. California has both lots of sun, high electricity prices, and many people parking outside of shade. Hawaii doesn’t get quite as much sun, but is paying 45.4c/kWh right now.
- macspoofing 4y ago
  >Justify why you think you can only stick a single 400W panel on a car. Because a 400W solar panel is basically the size of a car (~1mX2m). And under IDEAL CONDITIONS, you're looking at a 150 to 250 hour charge [1] ... and you're not going to get ideal conditions most of the time. Maybe you can stick 5 of those panels on a trailer and have the EV haul that around, and now you've improved your charging time from 250 hours to 50 hours (still, under ideal conditions) ... congrats, you still made negligible difference in extending EV range or making it practical. >Cars are large 3D objects, you aren’t going to get nearly as much power from side panels or the dashboard as the roof ... You're guaranteed to get 0 power from the sides that aren't facing the sun. So now you're horribly complicating the manufacturing process and increasing the EV price, all for an approach that would provide, at best, miniscule improvement to range. >How effective this would be in Alaska is irrelevant if nobody buys it in Alaska. It won't work in California either. But let's try something else ... with EV manufacturers being obsessed with squeezing out every km of range, why do you think approximately 0 of them are actually building an EV with built-in solar panels? What do you know, that they don't? [1] Assuming a 60kWh-100kWh battery and dividing by 400W = 150h to 250h
  - mattmaroon 4y ago
    Ha, nobody's camper has 2kw solar on the roof. You've got a huge installation if you've got half that. Your roof has ACs, skylights, vents, ect to work around. I've got a 35' travel trailer I live in 4 months a year (and that's close to as bit as they get) and I think I could get 1,200w up there if I really squeezed. I took some measurements because I'm planning to. RVs are often parked in full sun at least, but even then. I think I'd be lucky to get more than 5kwhh a day. Which is great for me as long as I'm not running the ACs. But that would not even remotely account for the extra drag it put on an EV to trailer it ten miles. There've been attempts to make "solar paint" for cars, which would be lovely if possible, but even then I think the economic argument will essentially never work out when you factor in time value of money. As the original article said, the economics will likely always be much better for putting the solar panels on your house and charging at home.
    - 4y ago
bluGill 4y ago
If installing on cars then we should assume the higher cost extra efficient cells that cost a lot more money. On a car or small truck there just isn't enough sunlight to make a difference even at 100% efficiency (last I heard labs were getting in the low 40% range using tricks that probably don't apply in the real world). However for large motor homes (and possibly semi trucks) there is enough roof space to make a difference. Motorhomes often stop for a few days at a time so can get some useful range (or at least not use the batteries running the stuff inside). In no case though is anyone thinking about saving money with solor on a moving vehicle. The large ones can possibly get enough range to be worth the extra costs even though it's costs more money.
mikestew 4y ago
Picking a daily perfect value and assuming that value scales to all days is not a good estimate. What I'm seeing on this topic is a lot of folks that I can only assume have never spec'ed out and actually used a solar installation. Go throw some panels on the roof of your house and RV, and then we can talk about how "all we have to do" is put panels on a passenger car. Not one of the "all ya have to do" crowd has mentioned how efficient their solar installation is, how the math works. Nope, it assumes a spherical cow, yada, yada, yada, and the sun is always pointing at a direct 90 degree angle to the panel. The 410W on our RV, for example, is good for recharging the house battery after running the microwave to make breakfast. If it's cloudy, you won't get to run the microwave for supper, but at least the lights can stay on. The most I've ever seen come out of that installation was 390W. I've not looked that hard at the charts, but I'd assume on average maybe 200W. A cloudy Seattle day? That's when we're glad we bought the bigger house battery.
- mattmaroon 4y ago
  Curious how many kwh per day, roughly, you're seeing on that 410w solar?
  - mikestew 4y ago
    I can't get you really good numbers without some work, but what I did do was look back when I knew it was not covered, and when we were actively using it regularly, and when the Seattle sun was at it's best: June and July. In other words, give the most charitable number possible. For reference, the panels sit flat on the roof and I do not adjust them during the day. With some quick-and-dirty visual estimates from the charts, I'm coming up with about .85kWh/day. Yeah, I know, but I looked at it twice. I went back and looked at some other time periods as a sanity check. And <1kWh/day is what we get. In the summer. Right now the RV is sitting in the drive with the panels uncovered, and the driveway is sloped and slightly angling the panels to that sad little January-in-Seattle sun. Yesterday the panels cranked out a massive 0.1kWh. That's right: enough to run a 100W light bulb for an hour. Despite all that, it's enough to run the microwave a couple of times a day (which is really the only large draw the RV has), watch some TV, run the lights at night. And if the panels can't keep up, that's what the giant-ass 300ah lithium house battery is for.

Retric 4y ago

Justify why you think you can only stick a single 400W panel on a car. Cars are large 3D objects, you aren’t going to get nearly as much power from side panels or the dashboard as the roof, but solar panels are cheap. Also, Mount Signal Solar had a 29.7%(average 2015–2017) capacity factor from it’s solar panels. That’s averaging 2.85kWh per day across multiple years from a single 400W panel. https://en.wikipedia.org/wiki/Mount_Signal_Solar https://en.wikipedia.org/wiki/Mount_Signal_Solar Obviously most cars would never approach that but buyers are going to self select for better areas. How effective this would be in Alaska is irrelevant if nobody buys it in Alaska. California has both lots of sun, high electricity prices, and many people parking outside of shade. Hawaii doesn’t get quite as much sun, but is paying 45.4c/kWh right now.

macspoofing 4y ago
>Justify why you think you can only stick a single 400W panel on a car. Because a 400W solar panel is basically the size of a car (~1mX2m). And under IDEAL CONDITIONS, you're looking at a 150 to 250 hour charge [1] ... and you're not going to get ideal conditions most of the time. Maybe you can stick 5 of those panels on a trailer and have the EV haul that around, and now you've improved your charging time from 250 hours to 50 hours (still, under ideal conditions) ... congrats, you still made negligible difference in extending EV range or making it practical. >Cars are large 3D objects, you aren’t going to get nearly as much power from side panels or the dashboard as the roof ... You're guaranteed to get 0 power from the sides that aren't facing the sun. So now you're horribly complicating the manufacturing process and increasing the EV price, all for an approach that would provide, at best, miniscule improvement to range. >How effective this would be in Alaska is irrelevant if nobody buys it in Alaska. It won't work in California either. But let's try something else ... with EV manufacturers being obsessed with squeezing out every km of range, why do you think approximately 0 of them are actually building an EV with built-in solar panels? What do you know, that they don't? [1] Assuming a 60kWh-100kWh battery and dividing by 400W = 150h to 250h
- mattmaroon 4y ago
  Ha, nobody's camper has 2kw solar on the roof. You've got a huge installation if you've got half that. Your roof has ACs, skylights, vents, ect to work around. I've got a 35' travel trailer I live in 4 months a year (and that's close to as bit as they get) and I think I could get 1,200w up there if I really squeezed. I took some measurements because I'm planning to. RVs are often parked in full sun at least, but even then. I think I'd be lucky to get more than 5kwhh a day. Which is great for me as long as I'm not running the ACs. But that would not even remotely account for the extra drag it put on an EV to trailer it ten miles. There've been attempts to make "solar paint" for cars, which would be lovely if possible, but even then I think the economic argument will essentially never work out when you factor in time value of money. As the original article said, the economics will likely always be much better for putting the solar panels on your house and charging at home.
  - 4y ago

bluGill 4y ago

If installing on cars then we should assume the higher cost extra efficient cells that cost a lot more money. On a car or small truck there just isn't enough sunlight to make a difference even at 100% efficiency (last I heard labs were getting in the low 40% range using tricks that probably don't apply in the real world). However for large motor homes (and possibly semi trucks) there is enough roof space to make a difference. Motorhomes often stop for a few days at a time so can get some useful range (or at least not use the batteries running the stuff inside). In no case though is anyone thinking about saving money with solor on a moving vehicle. The large ones can possibly get enough range to be worth the extra costs even though it's costs more money.

mikestew 4y ago

Picking a daily perfect value and assuming that value scales to all days is not a good estimate. What I'm seeing on this topic is a lot of folks that I can only assume have never spec'ed out and actually used a solar installation. Go throw some panels on the roof of your house and RV, and then we can talk about how "all we have to do" is put panels on a passenger car. Not one of the "all ya have to do" crowd has mentioned how efficient their solar installation is, how the math works. Nope, it assumes a spherical cow, yada, yada, yada, and the sun is always pointing at a direct 90 degree angle to the panel. The 410W on our RV, for example, is good for recharging the house battery after running the microwave to make breakfast. If it's cloudy, you won't get to run the microwave for supper, but at least the lights can stay on. The most I've ever seen come out of that installation was 390W. I've not looked that hard at the charts, but I'd assume on average maybe 200W. A cloudy Seattle day? That's when we're glad we bought the bigger house battery.

mattmaroon 4y ago
Curious how many kwh per day, roughly, you're seeing on that 410w solar?
- mikestew 4y ago
  I can't get you really good numbers without some work, but what I did do was look back when I knew it was not covered, and when we were actively using it regularly, and when the Seattle sun was at it's best: June and July. In other words, give the most charitable number possible. For reference, the panels sit flat on the roof and I do not adjust them during the day. With some quick-and-dirty visual estimates from the charts, I'm coming up with about .85kWh/day. Yeah, I know, but I looked at it twice. I went back and looked at some other time periods as a sanity check. And <1kWh/day is what we get. In the summer. Right now the RV is sitting in the drive with the panels uncovered, and the driveway is sloped and slightly angling the panels to that sad little January-in-Seattle sun. Yesterday the panels cranked out a massive 0.1kWh. That's right: enough to run a 100W light bulb for an hour. Despite all that, it's enough to run the microwave a couple of times a day (which is really the only large draw the RV has), watch some TV, run the lights at night. And if the panels can't keep up, that's what the giant-ass 300ah lithium house battery is for.