It's grid electric powered. The canopy doesn't do much.

Let's calculate:

  Guess that the canopy for each bay is 7 by 4 meters, 28m^2

  Sunny spots receive about 4kWhr of solar power per square meter per day.

  Solar panels might be 25% efficient.

  Total daily power: 28m^2 * 4kWhr/m^2/day * 0.25 = 28kWhr/day

  Model S has an 85kWhr battery, half charge is 42kWhr.

The SunTech panels [1] produce a nominal 295W and are 2 x 1M so in your 6 x 4M square you can put 12 panels, nominal output 3.5Kw, my system is 90% "efficient" (5.2 kW Panel rating, 4.7kW delivered to the grid) assuming the same that is 3.15kW delivered to the grid. over a nominal 6 hr solar 'day' that is about 18kWhr/day. So the duty cycle on a power station would need to be one fill up every 3 days. If the travelling is mostly on weekends I could see the stations getting a couple of fillups on the weekend and having 5 days of no visitors. Time will tell. It is handy that Elon's the primary stockholder of Solar City :-) Good discount on panels.

[1] http://www.solarsystemsusa.net/solar-panels/by-brand/suntech...

They're sizing the installations in partnership with SolarCity, one of Musk's other start-ups. They claim they'll be sized such that it will generate as much energy over the course of the year as the vehicles consume. Meanwhile, you're estimating power output from a CG rendering on a marketing page.

You could argue whether or not they're lying, but they're certainly not incompetent. SolarCity's sizing calculators take these (and many more) variables into account.

And, at many locations, solar cells mounted on the weather canopy charge your Model S with solar energy.

I'm sure SolarCity projects will be supplying more power than Teslas use, but not from these charging stations. (Unless virtually no one uses the stations, which is probably not the plan. There'd be no reason to install 4 parallel charging stations if you were charging less than one car a day. Another possibility is that they build car ports that cover many parking spaces in a lot to support each charging bay. That's not what the picture shows, but it would work.)

I can't find an original source for the idea that the stations will produce more power than they consume, but it appears, attributed to Musk, in both Engadget and Huffington post. Most other articles on the event don't have it. It seems to have come from an oral presentation.

The good news is, if a Tesla S goes about 2 miles on 1 kWhr of power and if an average person drives about 10k miles per year, that is only 14kWhr/day. Each bay would supply the typical power requirements of two Tesla S cars.

Update: The press release is out now, http://finance.yahoo.com/news/tesla-motors-launches-revoluti...

It clearly says the stations will make more power than they consume. So either they are huge compared to the picture, or Tesla S drivers aren't much for road tripping.

  generate as much energy over the course of the year as the 
  vehicles consume

jws guesses that each slot generates 28KWh/day. A ten slot charging station would only be able to charge three cars without going into the red. Tesla would have to build a lot of very oversized installations in a lot of sunny, rural locations to hit breakeven.

A simpler explanation would be that he's not telling the whole story, and that perhaps they have dedicated solar farms in development/deployment or something to that effect. Don't afraid to dream a little bigger, darling.

You bet your ass he quadruple checked those numbers.

I'm guessing that the supply at these stations will be much higher than the demand for charging, so they'll make up the cost of "free" by selling wh's back to the grid.

Again, this is a guess based on a CG rendering on their website. That drawing doesn't constrain Tesla's engineering talent in any way – even without using extra land they could put up solar shade structures over adjacent parking spaces.

Assume you've got a couple dozen slots, charging 100 cars a day. (Far, far fewer than an equivalently-sized gas station. If we're going to transition to an electric-only transportation infrastructure, then car changing stations are going to become a common sight)

That's 9 megawatt-hours a day. A random solar panel calculator I found guesses that would need ~2000KW of solar panel capacity. So you'll need 8,000 250 watt panels. That'll cover 9,600 square metres, (2.6 acres-- if you're lying them flat, which you won't. A big dedicated solar generation station will use tilted one-axis tracking, which will use a lot more ground space) and cost you (at $410 a panel) a cool $2.4 million.

(Google's big solar installation at Mountain View, the one that got so much press, was only 1700KW. Our tiny electric car charging station has to be 17% bigger than it.)

Electric car charging uses a lot of power. Solar is great, I love solar, but it's not space-efficient, or cheap. Either Tesla is going to build a national solar generation network on the scale of Germany's move into solar power, all on their own dime, or they're lying through their teeth about charging draw/solar production breakeven.

I don't think Elon Musk would green-light the "100% solar power" line without doing the math. Again: you can argue about whether he's lying, but I can guarantee you he knew exactly the scale of what he was promising. That makes it all the more impressive, imo.

Re:lying, I'm imagining at some point they'll transition over to "we buy 100% solar power for SuperChargers", which is fine by me since it's functionally equivalent to what they're doing now.

Perhaps solar in previously undeveloped areas would be better? I doubt that. Developing solar plants in undeveloped areas only to put the charging stations in urban areas (that is where the market demands them after all) hardly seems better than putting charging stations in urban areas and sticking some solar there too. What is there to be gained from not putting solar wherever you can?

That said, I think we should be plastering the land we already use with solar panels. Might as well put all those rooftops to use.

I also think there is likely a lot to see in the future of non-panel-type solar. That generally involves a much larger or smaller scope than panels though, "medium" sized doesn't work well.

Have you ever looked at satellite views of the US? There are massive deserts just begging for the shade of some solar panels or mirrors. No use in heating up all that sand.

It's not so hard to move the energy out of the desert either. Just run wires, or better, relocate an aluminum smelter from the grid to out near the solar array.

It's tougher than you realise. Energy is lost when transmitting power over long distances - like from a desert to an urban area. I'm not an expert but as I understand it there are major challenges. A lot of solar installations tend to be located where the power is used (next to data centres, on people's roofs).

Considering all the infrastructure that goes into keeping a fossil or nuke plant fed and cleaned and its power output distributed, I think if a solar installation has a net payback time of similar period we ought to be willing to invest a little in the distribution as well.

Why aluminium smelters? I haven't heard this before.

> we ought to be willing to invest a little in the distribution as well.

I agree. I've read that's it's a huge challenge though, which is one of the factors holding up the development of large scale solar installations in the desert. Another challenge is the variance and relative unpredictability of power generation which means batteries are needed to smooth out the peaks and troughs to balance supply and demand.

> Have you ever looked at satellite views of the US?

My thoughts exactly. I think looking at Europe could bring a new perspective into what does 'lacking space' mean.

http://physics.ucsd.edu/do-the-math/2012/08/solar-data-treas...

Each solar power system is designed to generate more energy from the sun over the course of a year than is consumed by Tesla vehicles using the Supercharger.

wtf?

1) Tesla isn't making money right now, so what's a little more money they don't have?

2) If Tesla goes bankrupt, what do they care about promises about free charging? If they don't go bankrupt, they will make it big, so what will they care about a few free charges? Practically zero-risk.

The article definitely made it sound like that would be the case. They might also be counting on charging people in cars other than Tesla ones.