Evaluating the Role of Heat Pump Water Heaters in Demand Response

Market penetration of residential heat pump water heaters (HPWHs) is accelerating due to advancements in high- performance designs, purchase incentives, and regulatory energy efficiency requirements in the United States. Electric utilities can aggregate and leverage these customer-owned flexible loads to provide grid services, such as demand response. However, replacing electric resistance water heaters (ERWHs) with HP- WHs introduces new challenges to grid service dispatch. The objective of this paper is to highlight conformance issues and grid service asset performance deficiencies that arise due to inherent HPWH characteristics. The results of this study show that the reduced energy consumption and slower response times of HPWHs, compared against ERWHs, limit their use in grid services, as do non-conformant responses to protocol messaging. To improve grid service planning, utilities need to account for restricted energy capacities and slower response times, and HPWH manufacturers need to ensure conformant behavior and accurate capacity reporting. The latter could be achieved by developing an ANSI/CTA-2045-B implementation guide for HPWHs. By addressing these concerns, utilities can better plan for flexible load-based grid service programs and manufacturers can provide higher quality products to appliance owners.