Central Heat Pump Water Heater Load Flexibility
Developing Thermal Storage Controls for Central Water Heating Systems in Apartments
Redwood Energy, LLC
Recipient
Arcata, CA
Recipient Location
2nd
Senate District
2nd
Assembly District
$1,168,221
Amount Spent
Completed
Project Status
Project Result
The project concluded in December 2025 after successfully deploying LOCUS technology across three affordable housing sites and completing a Final Report. The project demonstrated heat pump water heater load control using dynamic price rates provided by the CalFlexHub.
The Issue
Central water heating systems are usually both the largest peak load and largest annual energy load in an all-electric low-income apartment complex building in California. Because hot water consumption peaks in the morning and late evening, when rooftop solar arrays are less productive or unproductive, the consequence is higher energy bills, and greater emissions from non-renewable grid-sourced electricity and grid stress. On the other hand, none of the limited central heat pump control technologies on the market have real-time input parameters to reduce operational costs, greenhouse gas (GHG) emissions and grid stress while maintaining or improving tenant hot water services.
Project Innovation
This project demonstrated a new-to-market Load Optimization Control Using Storage (LOCUS) technology developed by ZYD Energy that enables flexible load management of central heat pump water heater systems (CHPWH) through hot water storage volume controls. The LOCUS technology uses optimization algorithms to automatically determine heat-pump water heater operation schedules based on hourly/sub-hourly electricity price or emission factors, as well as demand response signals and real-time operation conditions, while ensuring reliable hot water supply.
Project Goals
Project Benefits
The project optimized the energy efficiency and operating hours of advanced heat pump water heater systems enabling them to be load flexible which achieved annual average emissions, cost and energy savings in aggregate across all systems studied.
Affordability
The LOCUS can lower costs by shifting peak energy use out of high-cost times of the day and optimize performance of the water heater systems. Projected adoption of the LOCUS in 5% of multifamily units could yield annual energy savings of 57.6 GWh, annual peak load reductions of 12 MW, $25.3M in ratepayer energy cost reductions.
Affordability
The decreased CHPWH utility bills paid by Asset Management benefits the development with increased replacement reserves for fixing or buying new appliances.
Environmental Sustainability
Shifting the energy use of a CHPWH system to times where energy production in California is produced by more renewable sources can reduce greenhouse gas emissions. Projected adoption of the LOCUS in 5% of multifamily units could yield an annual savings of 26,382 metric tons of CO2e.
Subrecipients
ZYD Energy, Inc.
Franklin Energy Services, LLC
Ecotope
Greg Pfotenhauer
Gabe Krause
Lonny Grafman
Match Partners
Redwood Energy, LLC
