The Sunway TaihuLight computer uses 15.4 MegaWatts to provide 93 petaflops. That's 166 picojoules per flop. That number hasn't changed dramatically for years. That's why future supercomputers will need their own dedicated nuclear power plants.
The only way this will change is if we have a Kurzweil event where the energy per flop drops 5+ orders of magnitude.