I was under the understanding that coal and hydro were more flexible and hydro even being pretty responsive (just reduce the flow rate and build up the water le

I was under the understanding that coal and hydro were more flexible and hydro even being pretty responsive (just reduce the flow rate and build up the water level in the reservoir). But in any case, wouldn't the surplus just cause the price to drop, causing other power sources to just dial down production thereby stabilizing the price?