Don't Coal and Nuclear Plants Need Pumped Storage?
Generally, yes. Most of the pumped storage plants we have today were built last century, along with the growth in coal and nuclear power plants. Both coal and nuclear generator plants are slow to "throttle" up and down along with changes in load demand. They are inexpensive power sources so storing pumped water for later use is cost effective especially when it can generate power at peal times when rates ate higher. New technology and advanced grid balancing has eliminated the need for new pumped storage.
Pumped storage wastes over 25% of the energy it stores due to inherent inefficiencies, evaporation and other losses in the pumping process. Even with such massive waste, the power companies can still make a profit by storing energy at times when it is cheap, and then reselling it into the energy market at times when they are allowed to charge higher rates.