Two water heaters may be installed in series at a customer location, such that an output of a first (or storage) water heater is coupled to the input of a second (or primary) water heater, the output of which provides hot water to the customer location. During normal operation, only the primary water heater may actually heat water for use at the customer location. However, during periods of excess capacity, the electrical service provider may enable the storage water heater to store the excess electrical power that is generated by operating the power plant at higher output (which may be more efficient). Later, during hours of greater demand, the electrical service provider may disable the storage water heater used to store the excess capacity, whereas the primary water heater may operate normally. However, during the time of greater demand, the storage water heaters may provide pre-heated water to the primary water heater, which in-turn, may need to heat the water less or perhaps not at all.