Originally Posted by docmirror

Interesting. You start by saying you can charge your car with the solar power you 'create'. (I know what you mean, you capture it, not create it). Then you go on to mention 'plug it in'. A little back of the envelope math is in order. Using Tesla numbers, the 85Kw/h batt is good for around 300 miles. That breaks down to 283.33 W/m or at an ave of 50 mixed city/hwy lets say 14,667W/h per hour. A 30 min drive in a Tesla will use about 7300 watts, yes?

I've done my share of solar work, so I have a pretty good idea of charge rates, and efficiency. A decent solar panel with 350W STC rating puts out about nominal 240W at 80% irradiance(no one gets 80% irradiance unless they are in the middle of a high desert location like me at 8000' central NM). But, we'll give the benefit of the doubt. Call it 250W so four panels, on a 2 axis mount will give 1000W of pure DC power from roughly 9am-3pm every sunny day. But wait, that 6,000W of pure DC power @ 120 volts doesn't get to go into the car, it has to be converted to AC, to go in the plug, and then converted BACK to DC to charge the batts. So, the best case MPPT charge controller, and best case inverter on the planet run about 89% efficiency - each. (0.89X1000)x0.89 = 792W per day of usable AC power going into the receptacle. One plugs their Tesla into this AC source, and viola! we can now charge the car.

Here's where I lose track. I don't know squat about the charging mechanism of a Tesla. But I do know that our 30 min drive has used roughly 7.3Kw of power. We can charge at 220VAC and get a good 3.6 amps going. If the Tesla uses a good efficiency AC/DC converter(I assume) and they are also getting that 89% efficiency, then the battery is getting about 704WDC/h. If all goes right, and everything lines up just perfect, it will only take 10.5 hours to charge the car fully.

Now, I've been conservative on usage, and liberal on charge rates for a reason. Real world actual conditions tell me that Tesla will take more like 20Kw/h to run(lights, AC, radio, etc). Real world charge rates and irradiance I know for a fact never ever reach 80%. More like 60% is the norm(having built 3 systems from scratch). But lets split the diff and call it 70%. That means we now need not 10.5 hours to charge but ~14 hours. That's two full solar days during the equinox, and 3 days at southern solstice, maybe just possibly one day during the summer solstice. For the 30 min drive.

If we up the solar panel count, we can get better, but at what cost? 4 panels @ $200ea, plus MPPT cntl @ $400, plus inverter @ $1400(non-grid tie) just the bits is around $2600. If we add panels we need a bigger charge controller, and bigger inverter.

Two days to charge the car for a 30 minute drive? Face it, you are 'plugged in' to the grid, unless you have acres of solar, and many $$$$$$ tied up in solar collection. Yes, it has a payback, if you grid-tie and you have a roof full of panels(oops, no longer 2 axis motion, now you are down to 35-45% irradiance) you can sell back power to the provider at 25 cents on the dollar. It will be cost effective in about 22-30 YEARS. If you bought it for the tech, performance, and convenience, that was the right choice, because they aren't all that 'green'.
<edited to correct a bit of math>

Originally Posted by AWDGuy

My comment is because MY 996 absolutely sucked the soul out of me. Was fun to drive...when it wasnt broken, and well, after 2 engine rebuilds, I was done with that car

And yeah, I'm not one of those people. I mainly bought the car for it's no maintenance and the performance. Not having to ever go to a gas station is a bonus. Free supercharging is nice but I've used that once since I got the car and it was more to just try it out. My gas bill went from $300/month to maybe $40 & my electricity bill went up about $40/month. Once i test drove my friends RWD model I was pretty convinced the Porsche was going up for sale. The next week it was gone and I put my order in for the dual motor 3 and havent regretted one moment.

Love it so much that I am now waiting for their pick up truck to come out so I can replace the last ICE family hauler in my driveway.

Was funny...was at the track this weekend and parked beside some of the super cars, and more people gathered around the 3 than the Lamborghini. The kids especially were very interested in the car. Elon is making kids and children dream of owning a Tesla some day....I remember doing this with Porsche when I was 12. How things have changed.

Originally Posted by ion_berkley

FWIW, purely to illustrate that its entirely practical with todays technology to cover your daily commute with generation at point of demand i.e direct solar-> car charging, my 52mile daily commute averages 15-16kWh, which is almost exactly a 3 hour recharge on 240V AC power from the panels under which my car is parked in the day. Panels cost about 0.60dollars/watt, fully loaded cost of the system including industrial scale inversion+batteries+distribution and charging stations adds a fair bit more, but still under $1 a watt. Construction cost of the parking structure dwarfed the solar infrastructure cost. Clearly you have to build at scale to hit these kind of numbers, but thats not an issue for a typical new construction Class A office construction project. Its a nice model for future development, the gas station paradigm doesn't work well for EV's and thats unlikely to change in the short term, possibly not even the medium term. It does hit a ceiling at some point, a multistory parking structure has diminishing roof space to car space ratio as you add floors, and I think with current and short term future panel technology only a single or 2 story structure could provision an EV charger for every space with a useful power rating.

Originally Posted by AWDGuy

My comment is because MY 996 absolutely sucked the soul out of me. Was fun to drive...when it wasnt broken, and well, after 2 engine rebuilds, I was done with that car

And yeah, I'm not one of those people. I mainly bought the car for it's no maintenance and the performance. Not having to ever go to a gas station is a bonus. Free supercharging is nice but I've used that once since I got the car and it was more to just try it out. My gas bill went from $300/month to maybe $40 & my electricity bill went up about $40/month. Once i test drove my friends RWD model I was pretty convinced the Porsche was going up for sale. The next week it was gone and I put my order in for the dual motor 3 and havent regretted one moment.

Love it so much that I am now waiting for their pick up truck to come out so I can replace the last ICE family hauler in my driveway.

Originally Posted by docmirror

If you are buying panels for $0.60 per watt, you are doing better than anyone on the planet. Retail costs are about $0.90/watt, large quantity for mono panels are running $0.79/watt. I'd like to see a price offered for 60 cents/watt.

Originally Posted by AWDGuy

I charge every night to recoup the days loss. Takes about 2.5 to 3 hours to recharge the 100km I used during the daily commute. I'm sleeping in my bed while that happens.

Originally Posted by chsu74

Solar panels capture energy from moonlight?

Originally Posted by docmirror

That is an array 10 feet wide, by 36 feet long, under 80% percent irradiance, to charge ONE car 3 hours.

Originally Posted by AnthonyGS

Yes they get to burn coal, but don’t tell that to them. And China doesn’t care about pit or strip mining for REMs either.