Pumped hydro has 70-80% efficiency. I just looked up the number for a local one (smallish, ~180MW) and it claims 77% It operates on a weekly cycle, pumping up

Pumped hydro has 70-80% efficiency. I just looked up the number for a local one (smallish, ~180MW) and it claims 77% It operates on a weekly cycle, pumping up at night and weekends. You do need a hill to build one, though. But you don't need Putin.