I doubt those stations will store the power locally. My bet is that the solar system pumps power into the grid during the day, generating $$ for tesla. Then in the night, it draws from the grid since power is cheaper then anyway.

The way solar works in california for small installations is you just produce it and use it and whatever you do not use just send it to the electric company. If you need power you are not producing then you just take it from the electric grid. The electric company has to take your excess power (by law). The electric company then subtracts the power you put in from the power you use and only charges you for the difference.

So currently you do not have to worry about batteries or storage. You only have to worry about producing on average about as much as you use. The electric company does not have to worry about storage either because times of high sunshine always coincide with times of high electricity demand (due to air-conditioning).

So currently one can easily install and use solar without ever worrying about batteries or storage. If we ever get to the point where we rely exclusively on solar and wind, we will have to start worrying about storage, but this point is far off for now. Also, at that point the responsibility for storage will likely fall on the electric companies.

According to the article it sounds like the devices are hooked up to the grid, but use solar effectively to offset the cost - Musk claim they will feed more energy into the grid than they'll take out while charging cars.

The solar component is a stunt. Electricity is fungible. How about putting the solar plants where they work well (mountaintop? desert?) and the charging stations can just hook to the grid. Then they can get their electricity from any convenient source (local nuke plant for instance).

The argument about 'free solar' is almost an oxymoron. That electricity costs more per kwh than most any other source.

It is not a stunt. It is a direct counter to the anti-EV argument "Electricity is made from fossil fuels anyway, so by driving an EV you are just shifting the source of pollution to the power plant."

Tesla is attacking every single anti-EV argument in a very deliberate way and most of the attacks are strong successes.

It IS a stunt, in the sense that the solar feature is technically independent of the charging stations. The message is clear, but there is no necessary link between the solar elements and the place you go with your electric car to charge up. Placing them there is probably a worse decision that placing them optimally. That's makes it stunt.

And there is also a strong argument that the manufacturing and installation costs of solar farms has a long payback. They are a battery in that sense - energy invested in them slowly comes back out. PRobably petro-energy. So intially solar is a net negative in eco-impact. Same with wind.