Patent ID: 8768526

Claim:
A water heater controller for controlling a water heater to alter electrical demand while providing hot water for normal use, said water heater comprising an upper heater for heating an upper volume of water and a lower heater for heating a lower volume of water; said water heater controller comprising: a power control means for varying the power supplied to said upper heater and for separately varying the power supplied to said lower heater; a processor having a memory, said memory storing a load shift algorithm comprising instructions for varying power applied by said power control, said load shift algorithm specifying a reserve volume capacity for said water heater, a lower temperature sensor measuring a temperature of said lower volume of water and providing a resulting lower volume temperature measurement to said processor; means for determining a remaining volume capacity of hot water in said hot water heater; wherein said processor operates said power control device to control a temperature of said lower volume of said water heater in accordance with said load shift algorithm when said remaining capacity exceeds said reserve capacity.