Water Heating

Definition

Energy-efficient, load-shifting capable, electric HPWHs are designed to meet the hot water demands of residential households or small businesses. HPWHs pull heat from the surrounding environment and transfer it into the water inside the tank. HPWHs typically run off electricity and deliver hot water two to five times more efficiently than electric resistance, standard gas water heaters, or fossil fuel fired water heaters. Larger unitary systems such as 12 kW integrated heat pump water heaters for commercial applications are included.

Research Initiatives

Research Initiatives	Performance Validation	Market Analysis	Measure Development	Program Development
120V Residential
120V Commercial
240V Unitary
Split Systems and Small Form Factor
Low-GWP Refrigerant
Connectivity & Load Shifting

Opportunities

Storage HPWHs are a critical residential building decarbonization strategy, providing a cost-effective, electric water heating solution for load reduction and shifting peak during carbon intensive utility periods. There is enormous potential for load shifting and shaping, load management, and the resulting GHG reduction from shifting the heating schedule to times when the electricity grid has a lower marginal emissions rate and cost to operate.

Additional performance validation, measure and program development is necessary to accurately assess impacts and adoption pathways of split systems, 120V unitary, and solar-assisted models, as well as trends in upsizing storage capacity and utilization of integrated or master mixing valves. Standardization of first hour ratings for HPWHs and installer training regarding appropriate design and installation best practices to account for recovery rates of different HPWH solutions will be necessary to ensure satisfactory performance for all residential users.Significant gains have been made in developing best practices guides for the sizing and installation of HPWHs, however, additional research is required to assess design solutions and applications in common recirculation pump designs found in many California homes.

Shifting to low-GWP refrigerants (e.g., CO₂) offers increased performance, higher water storage temperature capabilities and other direct greenhouse gas (GHG) emission benefits to eliminate the impacts of refrigerant leakage. To support the market shift, new low-GWP performance validation, especially at higher storage temperatures, accompanied by mixing valves, will be necessary to inform updates to measure and program development.

Planned zero-emission regulations on residential water heaters in the Bay area and statewide are based on reducing indoor exposure to combustion gases to households. The assessment and attribution of non-energy benefits (NEBs) such as health impacts from air quality and the development of innovative solutions for increasing equitable access to HPWHs are important for supporting an accelerated transition away from gas water heaters.

Upfront cost is the most significant barrier to HPWH adoption in the most common opportunity, emergency water heater replacements. Identifying opportunities for cost-compression of equipment and installation costs is necessary for equitable and scalable HPWH market development. In addition, assessing existing and new, innovative financing mechanisms, deployment interventions and behavioral programs is critical to establish a sustainable and sufficiently capitalized incentive and that enable accelerated adoption of HPWHs.

Replacement of electric resistance WH (seven percent of the California market) and the new construction (NC) market offer the quickest opportunities for market adoption and total system benefit. Program designs that support electric resistance to HPWH incentives and approaches and NC builder approaches are needed to support these market sectors.

Barriers

HPWHs face many barriers but these barriers are mostly due to market and installation practices, not shortcomings in the technology itself. HPWHs have installation challenges and operational features not found in common gas storage alternatives that can make fuel-switching challenging:

1. Cost-effectiveness of HPWH fuel substitution can be impacted due to high HPWH equipment and installation costs, current electrical and gas tariff structure and/or grid integration incentives.
2. Plumbing contractors generally lack awareness of HPWHs and expertise in the design and installation, including the disposal of condensate, adequate airflow, and venting to ensure proper performance.
3. Electrical service or panel upgrades can be a significant cost barrier and may need load management strategies or deployment of 120V products to mitigate the expense of an upgrade.
4. Emergency replacements are the most common scenario for a new water heater installation in existing homes, which creates immediate cost, time and complexity barriers to conversion from conventional gas water heaters. Permitting processes and a need for a separate electrical contractor adds significant cost increases and delays in hot water restoration for the customer.
5. Split-incentive issues between property owners and rental ratepayers complicate the costs and benefits of HPWHs.
6. Space and noise issues can undermine the suitability of unitary HPWHs, requiring a smaller form factor or split designs or relocation.
7. The introduction of new low-GWP natural refrigerants will require reevaluating their performance, as well as addressing permitting barriers and perceptions of safety risks with local inspectors.
8. There is an absence of a savings claims infrastructure, including eTRM load shapes, rules for quantifying load shape benefits, rules for viable electric alternative (VEA) measures to replace gas appliances, and the coordination on refrigerant leak reduction efforts.

Definition

Domestic water heating (DHW) is among the largest end-uses poised for decarbonization. With all-electric heat pump water heater (HPWH) options, HPWHs have a higher efficiency than electric resistance alternatives and can achieve dramatic energy and greenhouse gas (GHG) savings, compared with natural gas alternatives. This group covers efficient, demand-flexible non-unitary DHW systems for non-residential applications (such as offices, hotels, healthcare, and food service) and multi-family applications. Hot water systems under this group may include a primary heat generation (e.g. heat pump), storage, distribution, pumping, valves, controls, temperature maintenance systems, heat recovery, and alternative heat sources (e.g. solar or geothermal).

Research Initiatives

Research Initiatives	Performance Validation	Market Analysis	Measure Development	Program Development
Split HPWH
Unitary HPWH
Load Flexibility Controls
Dual Fuel Systems
Distribution System Optimization
Heat Recovery

Opportunities

There are many different important targets of research, development, and market transformation across different technologies, designs, and market segments within this group, each with their own needs. These projects could be executed as field demonstrations, technology development, lab studies, market studies, modeling, market transformation tools, or novel program delivery mechanisms. The state of understanding and research needs may differ, based on design configuration (e.g. integrated, split, central, clustered), segment (e.g. education, hospitality, healthcare, office, food service, multifamily), or building vintage (i.e. new construction or retrofit).

Prospective studies may focus on:

1. Reducing DHW system energy use and improving efficiency, designing without backup or temperature maintenance electric resistance (such as return-to-primary configurations), and reducing the complexity of all-electric centralized HPWHs.
2. Innovative program designs that can bring benefits of HPWHs to disadvantaged communities.
3. Developing incentive programs for medium and large low-GWP commercial HPWH in non-residential and multi-family buildings. Innovative program designs to ensure the multiple value-streams of efficiency, decarbonization, and grid-integration are all actualized.
4. Demonstration of overseas HPWH technologies that use new low-GWP refrigerants and other form factors such as low-GWP integrated HPWH or 20 to 30-gallon integrated HPWHs for distributed point-of-use applications.
5. Installed cost and space requirements compression of HPWHs and storage tanks.
6. Field assessments and design of dual-fuel water heating systems to address the needs of high-load, rapid-recovery applications, such as existing commercial kitchens, relegating existing gas water heaters to back-up, trim, boost, or secondary to a primary HPWH.
7. Demonstration projects that utilize the cold air by-product of air-source HPs to supplementally cool conditioned spaces.
8. Demand flexibility controls demonstration and implementation guidance. Optimization of load flexibility controls to minimize energy costs and GHG emissions. Recommendations for streamlined onboard load shift programming for HPWH systems.
9. Automated, algorithmic load shift controls based on input parameters such as monitored system operation, system capacity, hot water loads, total building coincident electrical demand, and utility rates (real-time or fixed time-of-use).
10. New unitary commercial HPWH designs above12 kW that offer more versatility for application in existing buildings with features such as ducting options, additional operating modes that fully lock out the electric resistance operating mode for use upstream of existing heater, and integrated controls to optimize usage, cost, and GHG, based on time-of-use factors such as peak rate periods and utility flex alerts.
11. Bringing clarity to designers for cost-effective scenarios for drain water heat recovery and using recovered heat as a heat source reservoir for the heat pumps.
12. Incorporating integrated exhaust air or refrigerant heat recovery systems at the water heater or point-of-use equipment location.
13. Optimizing distribution systems through novel recirculation and load-matching control strategies such as automatic balancing valves, combined optimization of temperature modulation, variable speed pumps with integrated constant return temperature control or occupancy-based inputs, distributed isolating valves, and pipe insulation. Distribution system optimization will not only reduce the operating costs and energy consumption, but also reduce the necessary HPWH system size or temperature maintenance components.
14. Incorporating high-performance master mixing valves to increase thermal storage capacity and utilization, increase the tank water temperature stratification with continuous recirculation systems, and reduce recirculation loop heat losses through precise temperature control.
15. Innovative program pathways and strategies for supporting the remediation and upgrades of existing, recirculating DHW distributions systems (e.g. pipe insulation, pipe hangers, shower crossover repair, balancing, pump controls, etc.).
16. Improving system efficiency through clustered centralized systems that reduce pipe heat losses and improve water heater efficiency versus one large, centralized water heating and distribution system.
17. Enhancing energy density and load matching of solar thermal and photovoltaic (PV)-assisted water heater designs.
18. Increasing thermal energy storage density by using phase change materials for increasing renewable energy penetration and load flexibility.
19. Development of alternative techniques to mitigate legionella risk, enabling additional use cases for HPWH systems.
20. Innovative utility rate structures or dedicated metering to facilitate decarbonization by mitigating operating cost burdens on building owners.
    
    

Barriers

Commercial-HPWH systems are still in a nascent technological stage that continues to evolve. Existing gas-fired hot water systems comprise 85 percent of the installed base of commercial water heaters. Physical space, electrical infrastructure, and installed costs are major upfront barriers that have slowed HPWH adoption in retrofit non-residential and multifamily applications. Of particular concern are escalating operating costs and affordability, as the electricity-to-gas cost ratio per unit of energy is approaching 8:1, significantly higher than recent years. Other limitations include product availability of low-GWP four-season heat pumps, 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 heat pumps for mitigating cost and space requirements in multi-family buildings, but similar tools are needed for 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. Recirculation systems, although important to improve hot water delivery time and minimize water waste, can heavily impact water heater performance in central multi-family and commercial buildings. New programs have only begun to scratch the surface of addressing barriers to adopting commercial HPWHs.

Barriers to be addressed include:

1. Lack of diverse commercial-duty integrated heat pump products such as 120 to 200-gallon 120V HP HPWHs.
2. Lack of field performance data of various designs, configurations, and applications (including system reliability and cost-effectiveness).
3. Lack of easy-to-access case studies that span the diversity of buildings with commercial HPWHs (120V integrated, 240V hybrid integrated, indirect central HPWHs, and combined with complementing distribution strategies including point-of-use heaters, heat recovery, master mixing valves, balancing, etc.).
4. Regulatory barriers to R290 HPWH development and adoption.
5. Lack of statewide incentive programs for medium and large commercial HPWHs for businesses.
6. Lack of design tools to select, appropriately size, and model HPWHs outside of multifamily applications.
7. Minimal documentation and empirically determined hot water load profiles for various non-residential building types, important for developing sizing tools, design guidance, and regulatory updates.
8. Ways to streamline electrical panel upgrades to support HPWHs or using alternative technologies to minimize or eliminate the need for upgrades.
9. Lack of HPWH familiarity for building permitting authorities (and health departments).
10. Lack of coordination between trades (e.g., engineering design, electrical, and plumbing).
11. Lack of sector-specific knowledge in implementing HPWHs in disadvantaged communities (multi-family housing).
12. Changes in the tariff structure and/or grid integration incentives to mitigate cost-effectiveness concerns.
13. Lack of code readiness activities to support electric ready code requirements for all non-residential building types that utilize commercial water heaters.
14. Lack of demonstration, guidance, and simplified implementation procedures of dependable demand flexibility and load shifting controls.
15. Lack of trusted distribution system software tools and design guides.
16. Lack of trusted software tools and design guides to simplify solar hot water system designs.
17. Lack of consistency among code requirements related to hot water setpoint temperatures.
18. Lack of experience deploying drain water heat recovery, particularly with the variety of potential heat sources.
19. Lack of experienced practitioners who can bring quality commercial-HPWH systems to building owners.
20. Potential degradation of energy efficiency with improperly designed recirculation systems for large HPWHs.

Definition

Residential multifunction heat pumps (MFHPs) use an efficient compressor system to serve both space conditioning and water heating requirements of a household, typically configured as a primarily hydronic system. MFHPs can come in multiple formats. Two-function (or combination) heat pump systems serve space heating and water heating demands. Three-function MFHPs provide space cooling in addition.

Research Initiatives

Research Initiatives	Performance Validation	Market Analysis	Measure Development	Program Development
2-function: Water Heating & Space Heating
3-function: Hot Water, Space Heating & Space Cooling
Selection Guidelines

Opportunities

Residential MFHPs offer a novel pathway to decarbonization, providing an efficient alternative to existing gas-fired equipment or the current approach of multiple heat pumps (HPWH and a packaged central heat pump). MFHPs can potentially replace space heating, space cooling, and water heating with a single system, depending on the configuration and design. MFHPs have the potential to provide much higher total system benefits by extending the benefits of thermal storage to space heating (and potentially space cooling). In addition, the single heat pump may free up a home’s electrical panel capacity for other electrification uses and could be deployed with lower overall refrigerants than current heat pump practices.

MFHPs are relatively new to the US market, and, as a result, there are many opportunities to improve the understanding of their performance and impact on the residential sector. Opportunities for research include:

1. Laboratory testing of MFHPs to evaluate system performance in various applications.
2. Field demonstration / performance validation of MFHP in new construction and existing building applications.
3. Market assessment of MFHP for California homes, including cost and requirements associated with MFHP installation in new construction and existing buildings.
4. Assessment of the potential TSB value of MFHPs (energy performance, demand flexibility, fuel substitution, and refrigerant emissions) compared with the efficiency of single-function separate heat pump, HVAC, and water heating equipment.
5. Assessment of the bill impacts and customer economics of MFHPs (total costs of operation, operating costs under current rate structures, increased value of load shed, etc.) compared with the efficiency of single-function separate heat pump, HVAC, and water heating equipment.
6. Development of modeling tools to compare various MFHP types and guide program development and/or support early adopting market actors.
7. Understanding workforce needs related to upselling practices to customers, comfort level of installation, and maintenance needs.
8. Validation of customer amenity and confirmation that proper hot water temperature and space temperatures can be met.
   
   

Barriers

As an emerging technology in the US market, there are many barriers to MFHP adoption that could be addressed. Understanding the performance of MFHPs in the context of US homes, the development of testing and installation standards, and the development of equipment selection guidelines are all necessary for understanding the efficacy of MFHPs in meeting California’s decarbonization goals and encouraging MFHP use in California. Specific barriers include:

1. Absence of standardized testing procedures for MFHP evaluation.
2. Lack of MFHP product offerings compared to international markets, particularly those where hydronic heating is common.
3. Limited understanding of the capabilities of the MFHP system in managing occupant thermal comfort.
4. Absence of a standardized installation procedure and contractor/installer knowledge.
5. Absence of understanding of the efficiency of MFHPs compared to independent systems.
6. Need for market assessment of MFHP for California homes, including cost and requirements associated with new construction and retrofits.
7. Absence of MFHP modeling/design tools.
8. Lack of performance standards.

Definition

Commercial multifunction AWHPs serve water heating and space conditioning needs for multifamily or non-residential buildings. This multifunction category includes combination AWHPs that provide DHW and space heating only, as well as systems that provide space cooling. These systems use refrigerant to move thermal energy in air-to-hydronic distribution systems. They typically can provide two or three functions simultaneously.

Research Initiatives

Research Initiatives	Performance Validation	Market Analysis	Measure Development	Program Development
Combination: DHW and Space Heating
Two Function: DHW and Space Cooling
Multifunction: DHW, Space Heating and Cooling
Sizing Methodology
Modeling and Software Tool Development
Test Method Development

Opportunities

Multifunction AWHPs that can provide multiple hydronic services to a building can address efficiency and decarbonization market needs across the California multifamily and non-residential sectors. Opportunities for emerging technology research include:

1. Laboratory applications testing and field demonstration of various multifunction AWHP systems in new construction and existing buildings.
2. Sizing tool development based on building load inputs and development of multifunction AWHP performance maps.
3. Modeling and software tool development to be validated with laboratory and field demonstration data.
4. Assessment of electrical infrastructure impacts, especially in retrofit applications. Will multifunction hydronic heat pumps reduce the need for electrical service or panel upgrades when decarbonizing existing buildings? Can a multifunction hydronic heat pump use existing chiller electrical service?
5. Studies on retrofitting existing buildings with variable flow refrigerant systems with multifunction hydronic heat pumps. In applications where VRF systems are failing, multifunction hydronic heat pumps may be a cost-effective decarbonization solution with lower refrigerant charges.
6. Assessment of benefits in space, cost, energy, peak power and GHG emissions, relative to decarbonization solutions that rely on separate heat pumps for DHW, cooling, and heating.
7. Thermal energy storage integration and quantification of the amount of energy available for load flexibility.
   
   

Barriers

There are several barriers to multifunction AWHPs that could be addressed through emerging technology efforts:

1. Manufacturers, researchers, programs, and regulators need standardized test methods of combination and multifunction HPs with native controls that mimic real world conditions and operation for all products and all configurations.
2. Multifunction AWHP efficiency may not be as high as separate heat pumps for DHW, cooling, and heating. This requires improved understanding of how controls, heat recovery, and system design can increase efficiency in AWHPs that simultaneously heat and cool.
3. Impacts on occupant comfort are not known. This requires improved understanding of controls, capacity, and system design that can maintain occupant thermal comfort (e.g. determining whether simultaneous water heating and space heating loads being met).
4. Multifunction AWHP technologies are more popular in international markets, particularly those in which hydronic heating prevails. More research is needed to understand and address the barriers to entry in the US market.
5. Load flexibility of multifunction AWHPs has not been explored. Controls that incorporate function switching, thermal energy storage (dedicated or DHW volume), and load up/shed require modeling, development, and testing.
6. Early adopter approaches are often custom-engineered, site-built systems. Packaged designs are needed for design, equipment, installation, and commissioning cost compression.

Definition

Commercial hydronic heat pumps serve space conditioning and service water needs for multifamily or non-residential buildings with large heating needs, such as a commercial kitchen or a large office building. These may be air-to-water heat pumps (AWHP) designed as boiler replacements or water-to-water heat pumps, such as heat recovery chillers, which can provide partial heating and cooling for facilities with simultaneous loads. This technology family is focused on advancements of the product itself.

Note: This technology family will not focus on the holistic system design or interoperability with other large components, which are spread across several technology families.

The Water Heating SME team would like to note that this is seen as a lower priority within the Water Heating TPM and has a heavier HVAC focus.

Research Initiatives

Research Initiatives	Performance Validation	Market Analysis	Measure Development	Program Development
Heat Recovery Chiller
Air-to-Water Heat Pumps
Software tool development to support product specification
Test Method Development & Validation

Opportunities

Hydronic heat pumps can provide multiple hydronic services to a building to address efficiency and decarbonization market needs across the California multifamily and non-residential sectors. Opportunities for emerging technology research include:

1. Laboratory applications testing and field demonstration of various multifunction AWHP systems in new construction and existing buildings.
2. Measure development for heat recovery chillers and AWHPs to support partial or complete fuel substitution in large buildings.
3. Conducting cost benefit analysis of retrofitting existing buildings with VRF with hydronic systems.
   
   

Barriers

There are a number of barriers to hydronic heat pumps that could be addressed through emerging technology efforts:

1. While manufacturers have developed test procedures under AHRI 550/590, this test procedure has not been adopted by mandatory standards or voluntary standards, which limits the broad reach needed for this market adoption.
2. Load flexibility of multifunction AWHPs has not been explored. Controls that incorporate function switching, thermal energy storage (dedicated or DHW volume), and load up/shed all require data, modeling, development, and testing.
3. Early adopter approaches are often custom-engineered, site-built systems. Packaged designs are needed for design, equipment, installation, and commissioning cost compression.

Definition

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.

Research Initiatives

Research Initiatives	Performance Validation	Market Analysis	Measure Development	Program Development
Hot Tub Heat Pump Pool Heater
Residential Heat Pump Pool Heaters
Commercial Heat Pump Pool Heaters
Commercial Variable Speed Pool Pumping

Opportunities

Opportunities in this technology family will increase the 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:

1. Projects that demonstrate the emergence of new technical innovations, such as smart controls, variable speed, hybrid units, low-temperature operability, and staggered start-up capability with heat pump pool heaters (HPPHs).
2. Projects that demonstrate electrification of pool heating loads as part of home electrification service assistance. Projects may include those that have homes with photovoltaic (PV) solar or plans for PV to be installed soon.
3. Projects that encourage HPPH or solar-assisted HPPH adoption in new home construction or newly constructed pools.
4. Innovative pool cover projects that encourage the consistent use of pool covers to enable the wider adoption of HPPH. Project could include novel methods to reduce the installation and maintenance costs of automated pool covers.
5. Innovative projects to address electrical system requirements when the existing pool heater uses natural gas.
6. Innovative applications of HPPH to provide heating to inground spas. Projects that demonstrate the utility of hybrid HPPH to provide spontaneous heating.
7. Innovative projects to demonstrate ability of electrical system to accommodate startup surges due to HPPH compressor operations. Accommodation of other emergent loads on the home electrical system such as heat pump and electric car charging.
8. Projects that demonstrate the load shifting potential for both pool heating and pumping in coordination with proposed flexible demand appliance regulations by the CEC.
   
   

Barriers

HPPH installation face opposition where high electric rates discourage the 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 an 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. Emerging technology investments in this technology family can help bring greater awareness and highlight alternative decarbonization pathways.

Potential barriers studies should address:

1. Inconsistent design software
2. Ongoing practice to oversize heaters and pumps
3. Learning curve on pool heating operation with a HPPH, versus a gas-fired pool heater regarding set back temperatures.
4. Limitations based on health code requirements
5. Roof space for solar thermal competing with PV