> Would anyone here allow their Tesla to discharge when parked, allow it to feed power back into the grid?

I absolutely would, in fact it's a major reason I am not getting a Tesla and am instead opting for an EV that emphasizes its vehicle-to-home power capabilities (e.g. F150 Lightning and Lucid). I also know a ton of other Texans who feel the same way I do given our (deserved) lack of faith in our electric grid.

Also, saying it's "feeding power back to the grid", while technically accurate, isn't necessarily how I think this will be messaged. Instead, I think it will be messaged that, in times of high demand, your house alone will be powered by your car battery and taken "off grid".

Right now, some of the biggest issues with renewables is just timing during the day (e.g. late afternoon/early evening power needs peak right as the sun is setting). Telling people they'll get a substantially discounted rate if they allow their house to be "disconnected" from the grid for a few hours (because they have a car battery that can power their house) would be a big incentive to a lot of people.

But why involve your car? The logical thing to do is install a large lead-acid battery pack for the house, one which is dirt-cheap and won't suffer being charged/discharged. Lead acid batteries of a capacity equivalent to a Tesla can be had for a few hundred dollars. Lead-acids are also infinitely recyclable and don't involve the nasty/complex chemicals of lithiums. The ideal system would be to slowly charge the massive house battery whenever power is cheap, then dump it into charging the Tesla without drawing from the grid.

Because the point is the car already has a giant battery. A Tesla Powerwall has 13.5 kWh of storage, while a F150 Lightning battery has nearly 10 times that.

And yes, V2H power can increase wear on the battery, but my understanding is that large strides have been made (and certainly will be made) in reducing the wear impact on the battery.

What "nasty" chemicals are in a lithium battery?

Lithium batteries live longer than lead acid.

My company tried designing a unit that runs off a solar panel and battery. We initially designed around a lead acid battery. And as we kept accounting for things it just got larger and more expensive. We then switched to a lithium ion battery and it's literally a 1/3 the cost and a tenth the weight/size.

As we saw in Europe and Texas, electricity price could get insane extremely high for a short time so possibly power grid operator pays more. A problem is that some people want to hoard electricity on their vehicle in such situation.