We have one in Western Massachusetts (Northfield Mountain) built nearly 50 years ago to pair with the Yankee nuclear power plant in Vermont. Peak run-rate is 1140 megawatts and the hilltop reservoir is ~12k acre feet. Peak spin up takes ~10mins and can run for ~8hrs if the upper lake is full. So capacity is just short of 10 gigawatt hours.

My high school electronics class took a field trip there and I found the scale and design simplicity truly awe inspiring.

https://www.wbur.org/bostonomix/2016/12/02/northfield-mounta...