Note: Hydro power is different than pumped storage.  Hydro needs a river and a huge lake etc. Pumped storage can simply create a new lake on top of a mountain and pump water up there.<p>Colorado for example has a lot of high altitude lakes that are not used.  Ideal locations need to be close to high grid producers or users otherwise you need to build a lot of transmission lines.<p>Further, current usage is designed for peak power output not total storage, if the goal is 10&#x27;s of TWh we would want a lot of huge reservoirs with minimal pumping capacity each.  Where current designs are focused on peak output which is the expensive part.  So, massively increasing storage capacity would likely reduce costs per GWh stored.<p>Anyway, these numbers are going to have a lot of give based on goals.  The point is the US government can make this problem go away for ~2 billion &#x2F; year which means it&#x27;s not a significant issue.