Multi-Function Heat Pump Research Home Test – Variable Speed

California’s transition to electric homes faces many challenges. Upgrading space conditioning and water heating systems often encounter breaker panel limitations that significantly increase cost or derail electrification plans altogether. Around 30 to 65 percent of California homes are expected to need electrical-service-panel upgrades to fully electrify. Most service panel upgrade avoidance methods require sacrificing comfort, service, or convenience.  The multi-function heat pump (MFHP) is a single system that supplies both space conditioning and domestic hot water (DHW) needs. Combining these functions enables the use of a single electrical circuit, usually of similar capacity to an air conditioning circuit, allowing replacement of a furnace, air conditioner and gas water heater using existing electrical circuits. The combined functions also reduce peak power consumption and provide energy efficiency benefits over baseline equipment. This project performed side by side testing of an MFHP and a conventional electrification retrofit package that separately provides space conditioning and DHW through a heat pump HVAC system and heat pump water heater (HPWH) in a residential single-family test home in California climate zone 12. Data was collected across heating and cooling seasons to estimate annual energy use for both retrofit scenarios. The installation of the MFHP system required one 30-amp breaker while the conventional retrofit required a total of 85 amps across three breakers. The MFHP reduced the observed peak power draw by 32% but estimated annual energy use was comparable between systems. The lack of measured energy savings was attributed to control settings that were designed for the European market. Recommendations were developed to help capture the efficiency benefits in future U.S. product offerings.  The larger compressor capacity in the MFHP system provides faster water heating compared to the HPWH, allowing for smaller storage tank sizing without sacrificing comfort. This work has outlined the potential for MFHP systems to reduce barriers related to residential electrification while also offering efficiency benefits over incumbent technologies.