Exactly right. A peaker plant operates on the marginal rate difference, essentially time-shifting energy from off-peak production to times when demand (and thus wholesale cost) is highest. I’d like to see analysis of a wind-hydro peaker, in which wind would be used to pump water into a reservoir which would then be used to drive a hydro to produce electricity when needed. It seems vastly simpler and with much greater capacity than electrical methods, e.g. capacitor or battery banks.