Taking into account conversion losses and evaporation losses from the exposed water surface, energy recovery of 70–80% or more can be achieved. This technique is currently the most cost-effective means of storing large amounts of electrical energy, but capital costs and the necessity of appropriate geography are critical decision factors in selecting pumped-storage plant sites.
Coulnd’t we use solar to pump water into reservoirs, and then let the water flow through hydroelectrical dams when we need the electricity?
[yes](> https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity)
Oh wow, I had no idea this existed. Awesome!