[rbanffy]

It'll always be some marginal utility - the main purpose of the EV will always to be a car. You can use it to store energy purchased at non-peak hours so you can avoid using the grid at those times, something that'll probably raise peak prices, because if you need the energy right then, you really need it.

So, EV owners may use their cars to help reducing their energy costs and supplementing their PVs and fixed batteries (if any), but shouldn't expect a car to pay for itself like that.

[manholio]

But you will not use it if the depreciation on your car vastly exceeds what you could earn from the scheme.