Yes, due to Pumped Hydro's benefits... the major cost is the size of the generators.
A single 100MW turbine can store weeks-and-weeks of power if drawing from any small lake. But for it to be useful to a lot of people, you probably need to build a gigawatt scale turbine.
With that said, the Bath County generator is the largest in the world, and is close to 30 GW-hr of capacity (3GW of power. Yes, it can empty the lake in 10 hours, and refill it in another 10 hours)
About 118,000 cubic feet per second: 32,000 cubic feet per second for power generation and 86,000 cubic feet per second of valve discharge. One cubic foot per second of water equals nearly 7 gallons passing a given point in one second.
So, the operational storage capacity of Hoover dam is 2 GW * 2000 Hours = 4 Terawatt Hours. I realize these are entirely different projects, but it's interesting to get a gut sense of how incredibly large the Bath County generators are - not only do they generate power going down - they can also pump that water up.
A single 100MW turbine can store weeks-and-weeks of power if drawing from any small lake. But for it to be useful to a lot of people, you probably need to build a gigawatt scale turbine.
With that said, the Bath County generator is the largest in the world, and is close to 30 GW-hr of capacity (3GW of power. Yes, it can empty the lake in 10 hours, and refill it in another 10 hours)