Edit: Hydropower generally builds a huge dam to support a large head of water piled on top of it&#x27;s self.  Pumped storage replaces that huge column of water with hill so you only need a relatively small amount of water to store a lot of energy.<p>Anyway, I still think your numbers are a little high as Solar and wind are never going to have zero output over a day which reduces peek demands significantly.  Existing dams can also shift production to meet different sessional needs and act as backup power production.  Still, let&#x27;s call a ~200 billion investment enough to solve grid storage.<p>Further, current pumped storage can make money though arbitration. So, private investment subsidized by say 2 billion &#x2F; per year or 80 billion over 20 years seems to make this a non-issue.