Despite mentioning it some time ago I haven't had time to progress anything around V2G, V2H. So good to see you are. IMO using v.gen could be confusing as it is not strictly operating as a generator, that is closer to motor regeneration back into the pack. How about v2x instead which covers both V2H and V2G applications? 

Is the voltage metric required as my understanding is this will be the pack DC voltage? 

Given there is the possibility of V2H, so not grid connected could you instead have v.v2x.kwh.output and .input?

Cheers Derek