Heat Pump Water Heaters: Field Evaluation of New Residential Products

Heat pump water heaters (HPWHs) are significantly more energy efficient than standard electric water heaters, and can result in lower annual water heating bills for the consumer, as well as reductions in greenhouse gas emissions. HPWHs use the vapor compression cycle to transfer heat from the air into stored water. In the U.S. about 8 million residential storage water heaters are sold annually according to AHRI data [1], but for the past two decades, less than 0.1% of these have been heat pump water heaters. In recent years, several major U. S. water heater manufacturers (and some overseas companies) have introduced new HPWH products as energyefficient alternatives to standard water heaters. With improved product designs and promises of 3-6 year payback periods, new heat pump water heaters have the potential to make significant penetration in the residential water heating market. Starting late-2009, the most extensive field study in the USA was put in place to demonstrate the efficiency, reliability and performance of major modern HPWH models. Over 145 HPWHs and 27 baseline electric resistance water heaters were instrumented in residences in different climates across the country. Measurement data including system power and energy, entering and exiting water temperature and flow rate were recorded. In addition, to capture customer satisfaction, customer surveys were gathered before, during and at the end of the study. Results of this study will be presented to provide insights on real-world efficiency, reliability and customer satisfaction for HPWHs.