We have done one truly "whole house" generator. We did all the prep work wiring and panel wise, and the homeowner contracted directly for the generator. I don't know the size, but it was almost an Oversize Load on the 18 wheeler that brought it in. It is about as big (outside dimensions) as the one behind our local telephone company central office. The guy is phenomenally rich, so it didn't matter to him. I bet it cost more than my house easily. The darn thing is LOUD also.