This endeavor is really just the start of a much bigger movement.

Battery storage is vital for utilities looking to rely on solar energy even when the sun isn’t shining.

But storage is also increasingly important because as the amount of solar being built in Vermont has skyrocketed, customers’ energy use has become more variable and unpredictable.

For example, people might not need to draw electricity from the grid as much during sunny times, but if a cloud passes over, demand could shoot back up.

“You have solar and wind being installed, and in many cases these are a new type of power plants, but they’re not controllable, in the sense that you can’t ramp up and down solar or wind as you want,” says Mads Almassalkhi, an assistant professor of electrical engineering at the University of Vermont.

“So they’re not as well-behaved as our old-school traditional power plants.”

Almassalkhi says when you couple that with the fact that today’s electricity demands are more variable and change faster from minute-to-minute, “what that means is you have these slow generators that have to track this much faster moving [demand.] So this means … you have to have power plants sitting by, waiting basically to ramp up and down very quickly.”

That’s where utilities traditionally rely on natural gas plants. But batteries are also quite capable of ramping up and down quickly.

“One of the biggest challenges is intelligently coordinating hundreds, thousands [someday] of Powerwalls,” he says.“If we can regulate this in smart way, we can cancel out the variability that’s introduced from renewable energy.”

So far, Green Mountain Power has only installed about 10 Tesla Powerwalls in customers’ homes. But once all 500 are hooked up to the electrical grid, the utility will have a new source of power generation: The basement batteries will add up to about 1 megawatt of power.

That doesn’t seem like much when compared to the fact that in peak use times the whole state of Vermont demands over 700 megawatts. But every power source counts.

And there’s already nearly 150 megawatts of solar cranking in Vermont — enough to power more than 24,000 homes. So if utilities had more battery storage, all those basement battery packs could be a significant source of power.

Such a cool project

It really is. My only complaint about Powerwalls is that they're not happening quickly enough.