What's the power hookup to just boot one rack? I'd imagine that's more than you get anywhere in residential areas for a single house.
Depends on the residence. I have personally seen a large house in Brooklyn with dual 200 amp 120/208 volt three phase services (two meters, each feeding a panel.) I have seen someone setup an old SGI rack scale Origin 3000 systems in their garage. I think they even had an electrician upgrade their service to accommodate it.
Hopefully in 40 years we'll all be running miniature cold fusion power or something, so we can avoid burning the planet to the ground.