Demonstrating PCM TESS in Multifamily Central Water Heating

Retrofitting multifamily buildings with domestic hot water (“DHW”) recirculation systems to support efficient electrification, load shifting and demand response is challenging due to limited mechanical space, high upfront costs, and performance constraints.This project will validate the performance of phase change material (“PCM”) thermal energy storage integrated into multifamily DHW recirculation systems. By installing a distributed PCM thermal energy storage (“TES”) unit on one recirculation loop at a demonstration site, the project will evaluate how PCM impacts heat pump performance, recirculation losses, system efficiency, peak load, and load shifting capability. The project research will quantify operational benefits, confirm performance under real-world conditions, and provide actionable data to inform electrification and decarbonization strategies. By focusing on PCM’s ability to store thermal energy and deliver hot water during peak hours, this project addresses critical grid challenges and offers a scalable, cost-effective solution for space-constrained buildings.The findings of this project will inform central heat pump water heater (“CHPWH”) system sizing, design decisions, and installed costs, supporting broader adoption of electric water heating solutions. The project aims to show how PCM can enable faster, lower cost electrification in the multifamily sector. Ultimately, this project is intended to open the door to much broader CHPWH deployment by providing utilities, programs, contractors, and building owners with clear evidence of how distributed PCM TES can reduce retrofit barriers, improve economics, and support grid-responsive, all-electric water heating solutions statewide. Expected outcomes include validated performance metrics, insights into energy savings and load-shifting potential, and recommendations for integrating PCM thermal storage into efficiency portfolios. While the primary focus is multifamily housing, results may be applicable to other building types, such as hotels or office buildings, with DHW recirculation systems and electrification goals. This project builds on and informs the PCM distributed DHW operational concept developed in the prior California emerging technology program (“CalNEXT”) emerging technology project number ET25SWE0050, moving from design and modeling to practical implementation.