> I think I understand what they’re saying but it makes it sound wasteful Just in case it's not clear to anyone (or to you) they pump the water up the mountain

> I think I understand what they’re saying but it makes it sound wasteful Just in case it's not clear to anyone (or to you) they pump the water up the mountain with cheap (often renewable) energy when there's a surplus, and then release it instead of turning on the more expensive gas generators to fuel the peak demand.