Energy conservation isn't a five year payback?

Not according to Mike Burt.

“There are significant savings opportunities, but unlike commodity savings, they won’t be achieved in a year. It will take 10-15 years for the big savings to be realised and it’s difficult for ministers to grasp this as they deal in four-year time frames,” Burt told delegates.

I'm not sure I agree, but Burty's not explicit about what kind of retrofits and baseline he's talking about.