Sure, I understand that pumped storage is different technology but the reservoir + head infrastructure required for both is pretty similar and that&#x27;s what costs money. The turbines would be designed differently since you want dispatch-ability rather than peak output and the intakes would be a lot lower because otherwise you can&#x27;t actually use most of your capacity but otherwise you&#x27;re still talking about massive civil engineering projects either way.<p>Not only that, but the best sites have probably already been taken and if you want to build a massive amount more (by a factor of 50 or so) then you&#x27;ll get into more and more marginal sites.<p>Even in countries with a lot of lakes available near elevation change, blasting and tunnelling into rock to get the water from the high to the low reservoir is not cheap.<p>Assuming that you build one full day&#x27;s worth of storage (10TWh), for the sake of convenience we can convert this to power and say that we need 416 GW. You say that the expensive part is focussing on peak output, I actually disagree (because I think the civil engineering costs dominate) but let&#x27;s put a 50% discount on capital costs at the end to account for it.<p>Doing a little digging online, cost ranges for building pumped hydro go from $600 - $2500 &#x2F; kW. Let&#x27;s take the lower number and further halve it to account for what you said about energy maximising storage being cheaper than power maximising.<p>If we need 416 GW, that&#x27;ll cost $208 billion US dollars to build.<p>To be honest I went into this thinking that the cost would come out to be ridiculous but I&#x27;m not actually sure that is an outrageous cost. It&#x27;s only a fifth of the US annual federal discretionary budget.<p>If those cost assumptions actually added up which I&#x27;m not sure they do.