Also, just picture the mass graves that would have to be dug to deal with the hundreds or even thousands of bodies from things like Battle of New York.
"He may have slammed an entire planet into the alien overlord's space castle, killing billions and wiping out a thriving, intelligent, peaceful species, but hey, he saved Earth so it's all good!"
It would probably only take a little bit of time to figure out ways to store the energy so that all of society could run without the superheros continuously working shifts and stuff: like maybe they just reheat a molten salt core from time to time, or fill up a high altitude lake with water upstream from some hydro plants.
Wasn't Tony Stark going to scale up the Arc Reactor in first movie for clean, limitless energy? Instead, he fought a radical environmentalist to close his story.