to sustainable levels of consumption.

The energy crisis model is sorta based on the American "need" to consume 1.21 gigawatts of power per person. Finding sustainable ways to do that is probably a much more difficult problem than the mere expediency of cutting those 1.21 gigawatts down to, say .35 gigawatts. Not just by being more efficient, but by wasting less.

(BTW 1.21 gigawatts is not a serious estimate, just the amount of energy required by the flux capacitor for time travel.)