The existing standard of living requires exponential growth and unbounded resource consumption. It isn't possible to maintain that while reducing energy consumption "almost completely." This isn't Star Trek where you can just outsmart the laws of thermodynamics and run everything on free energy and vibes.
A "raging environmentalist" should understand that, particularly given that climate change and the collapse of the ecosystem is already underway. The window for "Manhattan project" scale solutions passed decades ago, the only solutions available now are damage mitigation. The future is going to be about maintaining our survival and civilization, not a reasonable standard of comfort.
