Efficiency is great but it's hard - going from 20mpg to 40mpg is twice as hard as going from 10mpg to 20mpg. Efficiency gains are frequently trade off gains -

Efficiency is great but it's hard - going from 20mpg to 40mpg is twice as hard as going from 10mpg to 20mpg. Efficiency gains are frequently trade off gains - in the best case scenario you're giving up something you don't need for something you want; sometimes though what you don't need now and what you don't need in the future are two different things. I'm not knocking any of that but I think we should be clear eyed about it. Further there are alternatives to efficiency - increasing the absolute amount of energy produced for one. That comes with problems obviously but it also opens up a lot of possibilities that increased efficiency does not.