Hydroelectric pumped storage seems very inefficient. Aren’t they working on better ways to store electricity or convert it to hydrogen?
It is not inefficient at all. Two major aspects are free. Gravity, and water. In places like California the night time demand is much smaller. Excess electricity from high load constant sources like nuclear, power the pumps that move the water back up in to the reservoirs.
Electrolysis and storage of hydrogen is hugely inefficient and very expensive. Then again... That’s just what the government wants.