Turning a Hot Tub into a Time Machine

Assuming a Hot Tub Time Machine has the same energy requirements as Back To The Future's DeLorean, what kind of upgrade would it need?

March 31, 2010
4:29 PM EDT
The cast of Hot Tub Time Machine (Rob McEwan/IMDB).
DeLorean DMC-12 Head on photo with doors open (Kevin Abato/Wikipedia).
Artist's impression of a wormhole linking two locations in space. Wormholes may also link two moments in time, allowing time travel (HSW).