Yeah, this is the "smart grid" concept that has been touted for years. If your washing machine knows the electricity price, it can run at optimal time, stuff like that. Unfortunately the dollar savings per person per year is way too low for people to bother, rather pay 30 cents extra to have the washing finished when you want it. So stuff like gamification has been seriously researched and tested as an option to make it fly. I think the jury is still out on it as a concept.

I would imagine EV charging could be a big consumer of this spare energy in the near future, especially with predictable commuting and same day weather forecasting.

Working in the energy space, I don't know why a driver would want this. It's the same problem with V2G schemes. It means that you could decide on a whim to go for a drive, walk out to your car, and find that it has no charge.

Well, first of all, keeping lithium batteries at 100% is hard on them, to the point where some devices lie to you about 100%. So staying at 75% and then topping up when it's cheap might not be the worst thing. The big deal would be is that you'd have to have a way to communicate with your car that you're going on a road trip Saturday 7:30 am/ in three hours and the battery better be all the way full by then or else.

I saw some pundit conversations about Battery Day recently. There's some speculation that a 'million mile battery' may be coming due to union of a few different complementary improvements to the battery design and manufacture.

If your battery can survive four times as many discharge cycles as the drive train, hooking back into the grid isn't so bad as long as your car doesn't conk out 10 miles shy of Grandma's house.

You don't think with all of today's technology there could be a solution where the driver sets charging thresholds and time windows reflecting their needs?

Yes, that could be done but it requires setting that up beforehand. In the scenario I outlined, deciding to go for a drive on a whim, i.e. not pre-planned, this is still a problem that technology cannot solve.

You have a car with a 200 mile battery. You have a minimum threshold that you'll pay any price for (say 80 miles), and if your a miser / want a deal / want a sale , you'll let your car be charged opportunistically when it's cheap for the rest of it.

If you know your going to be parked at the office for the most part for 8 hours a day, then you'd probably be ok putting your car in opportunistic mode as long as you have enough for your commute.

The car can also track your driving patterns and manage all of this seamlessly. Having worked at a gas station and seeing how people swarm my station when gas was $0.10/litre less than the surrounding stations because we didn't update fast enough, I think there will be plenty of price chasers for these modes.

The anxious / I drive for recreation types / road trippers can pay extra to stay topped up all the time.

I don't know about you but the number of times I had to drive my car until the tank is empty on a whim is pretty close to zero and even if I was stuck with an EV and I had to suddenly drive 300km I could always just go to a fast charging station to charge the car quickly.

In theory, automation should make a lot of this easier, which why something like a datacenter could be a productive place to start— it's not like a mine or some other industrial setting where turning down capacity in response to changes in the electrical grid suddenly means you have a bunch of people who showed up for their shift twiddling their thumbs instead of working.