Published December 15, 2023
Effective January 1, 2024
The decarbonization of water heating has been identified as an achievable and significant step toward California’s overall decarbonization goals, and policies are changing to emphasize this end-use. Programs like TECH Clean California and BUILD are working on the market transformation of water heating and water heating manufacturers continue to make key strides in Heat pump products to address electrical infrastructure challenges and space constrained spaces.
The electrification of water heating presents a key opportunity to build demand flexibility into this added electrical load: this make-or-break moment could result in either added stress on California’s electric grid in the crucial evening hours or true success in bringing grid interactivity to the mass market.
Efficient, demand flexible, electric HPWHs are designed to meet the hot water demands of residential households or buildings with similar water heating needs. This technology family will help meet the California Energy Commission’s goal of installing at least six million heat pumps by 2030.
Unitary and Split-System HPWH for single family and individual multi-family dwelling units; low-Global Warming Potential (GWP) refrigerants for residential-duty HPWH; 120V plug-in HPWHs; and grid and utility integration for connected residential-duty water heaters.
Note: The updates to this subgroup include 120V plug-in HPWHs; as they are now available on the market from two manufacturers, and grid and utility integration for connected residential-duty water heaters as the previous Grid Integration & Market Intervention technology family was removed, with this technology being the best fit.
Storage HPWHs are a critical residential building decarbonization strategy, providing a cost-effective, electric water heating solution for load reduction and shifting during peak utility periods. The potential for load shifting and shaping, load management from scale of day to half-hour, and the resulting GHG reduction from shifting the heating schedule(s) to times when the electricity grid has a lower marginal emissions rate and cost to operate.
Shifting to low-GWP refrigerants (e.g., CO2) offers increased colder climate performance, higher water temperature capabilities and other direct greenhouse gas (GHG) emission benefits due to the risk of refrigerant leakage.
Assessment and attribution of non-energy benefits (NEBs) (e.g., reducing indoor exposure to combustion gases) and development of innovative solutions for increasing equitable access to HPWHs and load flexibility programs.
Assessment of innovative financing mechanisms, deployment interventions and behavioral programs that enable accelerated adoption of HPWHs.
Evaluation and adoption of new 120V plug-in models and support for HPWH manufacturer product improvements to address known electrical capacity constraints, installation complexity and costs, facilitate adequate airflow and/or venting, decrease unit size (for space-constrained scenarios), and increase capacity and efficiency.
Technical performance of 240V unitary HPWHs is generally well-known due to mature testing and rating systems. With the emergence of 120V plug-in and split HPWHs, performance and suitability of existing testing and rating systems is less known.
Consumers and contractors general default sizing metric of tank capacity is insufficient in comparing gas heaters and HPWHs and especially 120V plug-in models. Industry-wide transitions to first hour rating (FHR) or another metric to account for the lower British thermal unit per hour (BTU/h) ratings of HPWHs will be necessary to ensure similar performance across products.
HPWHs have installation challenges and operational features not found in common gas storage alternatives that can make fuel-switching challenging:
The 2022 Water Heating revisions consisted of four opportunities and two barriers. As this market has expanded and matured there are more specific areas to focus on for opportunities and more barriers have come to light, therefore the SME team has made these several additions. The key changes to this technology family for 2023 include:
Efficient, demand-flexible electric water heating systems for non-residential applications (such as offices, hotels, healthcare, and food service) and multi-family residential applications (typically ≥5 dwelling units).
Central HPWH systems for multi-family, hotel/motel, food service, healthcare, and non-residential buildings; low-GWP refrigerants; dual-fuel water heaters; demand flexibility; grid and utility integration for connected commercial-duty water heaters; financing mechanisms; deployment interventions.
Note: The updates to this subgroup include non-residential buildings; to catch all applications, demand flexibility; grid and utility integration for connected commercial-duty water heaters; as the previous Grid Integration & Market Intervention technology family was removed, financing mechanisms; deployment interventions as these are available on the market now.
Water heating is among the largest footprint end-uses positioned for decarbonization with all-electric HP options, with greater efficiency than electric resistance alternatives and source energy savings over natural gas alternatives. HPWHs are an emerging technology with new products reaching the market such as large water storage capacity hybrid water heaters and large heating capacity low-GWP refrigerant HPs.
HPWH systems present the potential for efficiency and demand flexibility with appropriate system designs that consider storage volume, system configuration options, HP heating capacity, primary heater design, heat exchangers, temperature maintenance systems, controls, and draw patterns. The potential for load shift, shape, and shimmy: demand flexibility on a scale of day to half-hour and GHG reductions resulting from shifting heating to times when the electrical grid has a lower marginal emissions rates and cost to operate. Prospective ET studies may focus on:
Commercial-duty HPWH systems are still in a nascent technological stage that continues to evolve. Physical space, electrical infrastructure, installed costs, and operating costs are some of the biggest limitations that have slowed fuel-switching in retrofit applications. Existing gas-fired hot water systems comprise 85 percent of the installed base of commercial WH. Other limitations include product availability of low-GWP four-season HPs, weight, and noise. Manufacturers and distributors have started to address the barriers of design complexity, installation, and commissioning through the development of factory-built and commissioned skid and packaged systems that can be scaled for a range of applications.
Researchers and design firms have developed better sizing tools to right size HPs for mitigating cost and space requirements in multi-family buildings, but similar tools are needed for the many other commercial HPWH applications. Current health department sizing requirements do not address the use of HPWH systems in commercial kitchens and do not account for storage volume as a factor in sizing water heater capacities. New programs have only begun to scratch the surface of addressing barriers to adopting commercial HPWHs.
Barriers to be addressed include:
Note: The 2022 Water Heating revisions consisted of two numbered opportunities and five barriers. As this market has expanded and matured there are more specific areas to focus on for opportunities such as improving the efficiency (for operating cost parity with natural gas-fired heaters) and more barriers have come to light, including lack of diverse heat pumps products, lack of field performance data, among many other barriers listed above, therefore the SME team has made these several additions. The key changes to this technology family for 2023 include:
Distribution system and point-of-use design strategies and alternative heat sources to advance energy efficiency, water conservation, and GHG benefits.
Recirculation systems; heat recovery systems; master mixing valves; thermal energy storage, residential, commercial, and community-scale solar and geothermal water heaters.
Opportunities in this technology family will increase energy efficiency and demand flexibility through well designed hot water recirculation and heat recovery systems and the use of thermal energy storage systems and master mixing valves. Prospective ET studies should include software solutions, design guides, or field monitoring studies with these auxiliary components that address:
Alternative hot water design strategies are an important approach to decarbonize many “hard-to-electrify” water heating scenarios. Recirculation systems, although important to improve hot water delivery time and minimize water waste, can heavily impact HPWH performance in central multi-family and commercial buildings. ET investments in this technology family can help bring greater awareness and highlight alternative decarbonization pathways.
Potential barriers studies should address:
Note: As ideas have been brought to market, new ideas have been formed resulting in an increased number of opportunities and barriers identified. It has also been seen that recirculating systems can be designed and installed, poorly resulting in increased heat loss through the large amount of surface area or stratification in tanks. The key changes to this technology family for 2023 include:
Electric pool heaters for residential and non-residential pool markets; pool pumps and pool controls designed for the residential and non-residential pool market to increase efficiency, performance, and enable load shifting; and alternative strategies for pool heating and maintenance. The technology family will help support the development of all-electric codes and ease pool heating loads to improve grid resiliency.
Note: This family is eligible for a Focused Pilot TPM project. This family was added to avoid a scenario where a new home has a gas line only for the pool heaters. The local reach codes program had heard that concern, which lead to the development of a cost effectiveness report comparing gas-fired pool heating to heat pump pool heaters and solar, which allows local jurisdictions to develop cost effective reach codes.
T24 2025 has a proposed measure to disallow gas-fired pool heating to be the primary source of heat.
With these two efforts the program team felt it was appropriate to support the transition away from gas-fired pool heating.
The smaller group that developed the language for this new family rated the priority as high, but after discussing this with the larger group, it was agreed that the priority could be reduced to medium as pools are a luxury item, so not in every home, but still a large gas user and important for decarbonization.
Residential and commercial electric pool heater equipment, HPPH, solar assisted HPPH, pool automation systems for pool pumps, and pool covers.
Opportunities in this technology family will increase efficiency with optimized equipment and designs, including optimized electrification of pool heating loads, pool operation controls and the incorporation of load shifting of electric pool loads. Prospective ET studies should include controls solutions, design guides, or demonstrations that address:
HPPH installation face opposition where high electric rates discourage adoption of electric heating.
HPPHs lose heating capacity as temperatures decrease. While not a concern for spring, summer, and fall heating seasons, many climate zones within California present challenges to economical heating from HPPHs during the winter months due to increased heating load and decreased heating capacity.
Alternative hot water design strategies are an important approach to decarbonize many “hard-to-electrify” water heating scenarios. ET investments in this technology family can help bring greater awareness and highlight alternative decarbonization pathways.
Potential barriers studies should address:
Please refer to the Emerging Technologies Coordinating Council for a complete list of active and completed projects to ensure your project is not duplicative.