Green go kart options?

Depending on the length of the race Electric would be very fast, there's a guy at our local track that has built an electric kart and plays around with it, cant actually race it because there's no class for it but its running the same times as the KT 100s on a sprint track, but then again he races karts and knows how to drive, and the fact hes an electrical engineer doesn't hurt either, unfortunately the motor,battery's and speed controller are not cheap, things a trip, no noise and haulin butt.