A substantial fraction of the electricity consumed in the residential sector is used to heat water. Indeed, it is the second-largest single end use of electricity next to space heating. Due to the sheer size of the load there is substantial opportunity for energy use reductions. Recognizing the importance, heat pump water heaters (HPWHs) have been an integral component in Northwest power plans for nearly thirty years (NPCC 2010). The introduction of a new generation of integrated HPWHs, in conjunction with the Northern Climate Heat Pump Water Heater Specification, over the past five years, has enabled those savings to be realized (NEEA 2012a).