Recently released 120V heat pump water heaters (HPWHs) bring retrofit-ready products to the market, empowering consumers who wish to install these high-efficiency products but don’t have easy access to 240V/30A electrical service. Adding new electric water heaters may exacerbate existing electric grid peak load challenges. Since HPWHs typically employ 50-80 gallon (189-303L) storage tanks they are a form of thermal energy storage (TES) which is already present, and can be leveraged without purchasing/installing additional TES products.
Load shifting controls, which intelligently adjust the state of charge of the available TES to avoid electricity consumption during peak times, for 120V HPWHs are critical for maintaining a stable electricity grid. Prior research has indicated that the most effective way to change consumer electricity consumption is to leverage utility programs implemented by third-party aggregator companies. Utilities have begun releasing time-varying electricity prices, and utility programs shifting loads in response to prices can maintain grid stability while reducing participant electricity bills. To increase adoption load shifting control strategies must 1) leverage currently available HPWH capabilities, 2) provide incentives to participants by reducing their electricity bills, and 3) be easily adapted to existing utility programs. LBNL’s CalFlexHub and Stor4Build projects have developed cloud-based control algorithms that minimize occupant utility bills by creating customized load shifting signal schedules in response to a specific home’s time-varying electricity price profile and typical electricity consumption patterns. The control algorithms are capable of using either CTA-2045 or manufacturer API communication protocols.
Field demonstrations deployed customized CTA-2045 signal schedules in 10 homes in response to 5 different electricity price profiles. Two electricity profiles represented summer and winter dynamic pricing scenarios, similar to the new or upcoming opt-in pricing programs offered by Pacific Gas and Electric Company and Southern California Edison. Three of the price profiles were 2024 time of use rate schedules offered by Californian utilities. The demonstrations showed that these techniques can shift 29-54% of the load away from peak periods, and reduce 120V HPWH electricity costs by 8-46% depending on the electricity price profile. Price profiles with high differences between the low and high price times show greater impacts. Simulations showed that adopting CTA-2045-B, with the Advanced Load Up feature, would increase the cost savings by 21 percentage points and the peak period consumption reduction by 31 percentage points.