I want to replace peaker plants with storage. Somehow I don't think the economics work out. Do you disagree?

Even if we rebuild the whole continental US power grid (that's a lot more than $50 billion) to cope with the demands of using storage, it is unclear to me if we can build enough hydro to replace peaker plants. Apparently all other storage technologies other than hydro are cost-ineffective and/or do not have enough scale to solve the problem. Do you know if there is enough geography to go around for all the hydro we need or if there really are any cost-efficient alternatives?