That's more like billing resources as needed, rather than actually spinning them up. The resources are always spinning.

Yep, exactly that. I know most of HW can go on power-save on idle states, but still drawing some 5-15W of energy doing nothing. We need some kind of "e-ink" for web resources which doesn't change much but just need to be reached occasionally/on-demand, with a slight unsuspend delay of course.