Well, we can’t control how much heat there is (though we have found we can increase the average pretty effectively!) but we do have ways to control where it is.

Well, we can’t control how much heat there is (though we have found we can increase the average pretty effectively!) but we do have ways to control where it is. E.g., in our house we just got heat pump water heaters that are basically air conditioners that pump heat from the room (which the furnace puts its waste heat into, btw) into the water tank instead of venting it outside.