That's 3 minutes of maximum generation at https://en.wikipedia.org/wiki/Ludington_Pumped_Storage_Power_Plant https://en.wikipedia.org/wiki/Ludington_Pumped_Stor

That's 3 minutes of maximum generation at https://en.wikipedia.org/wiki/Ludington_Pumped_Storage_Power_Plant https://en.wikipedia.org/wiki/Ludington_Pumped_Storage_Power... I guess that plant doesn't have an extreme amount of head or a particularly large reservoir. It's about 7 minutes at https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Station https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Sta... , which has a lot more head. So you need a lot more pumped storage if you want to start talking about days of backup, and we already used quite a few of the best sites.