For those batteries that are still in-use, I think it’ll be a tough sell for homeowners to shell out the additional expense of bi-directional charging equipment….unless the car owner gets to sell the electricity at the current spot rate when there is excess demand. Otherwise you’re likely looking at a long payback on the extra expense of the bidirectional charging equipment. Though at a largest enough scale the additional expense is likely to be minimal, but going to have to get enough people to take the plunge first.