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Reliable hot water is critical for restaurants for preparing food and washing dishes and equipment, as well as hand washing.

However, water heating is one of the biggest energy users in restaurants. Heating water for restaurant use accounts for 16% of all commercial gas usage in California. Food service buildings are among the highest intensive energy users on a per-square-foot basis, largely because of their hot water usage. Foodservice operations may soon feel the pressure to electrify. The California Air Resources Board is analyzing proposed zero-emission GHG standards for new space and water heaters. It is currently planned for consideration in 2025 with any implementation beginning in 2030, and would only be applicable to the purchase of new equipment

Doing so will be difficult, particularly for existing restaurants. Many food service operations, especially small and independent businesses, do not have the space for the size of a storage tank that would be required for a heat pump water heater. Restaurants in California, as with most states, are legally required to have sufficient hot water to meet all these demands under peak conditions.

In response to these challenges, an emerging technology, the heat pump-assisted water heater, is gaining traction. It is designed to meet this existing gap between what the market needs and the cost and challenges of installing available heat pump water heaters. It is geared to meet the needs of existing food service businesses that want to be able to transition to a heat pump while still retaining the benefits of their current water heating system.

With funding from CalNEXT — California’s statewide emerging technology initiative — the TRC Advanced Energy team recently published a report, “Market Potential for Heat Pump Assisted Hot Water Systems in Foodservice Facilities.” This report, which TRC Advanced Energy developed with research support from Frontier Energy and Energy Solutions, assesses the benefits and challenges of adopting heat pump-assisted water heater technology for a range of food service establishments.

“Heat pump-assisted water heaters are a solution that we have available today,” said Amin Delagah, Associate Director of Research and Consulting for TRC Advanced Energy, an environmental services provider. “Heat pump water heater adoption rates in restaurants are still very low due to a lack of familiarity, space and electrical capacity requirements and primarily, the health department water heater sizing regulatory barrier, but the heat pump assist concept is a solution that we can move forward today to overcome these barriers.”

The heat pump-assisted water heater, as its name suggests, is designed to operate in series with an existing water heater, which makes it attractive for restaurants that do not want to overhaul their current system completely. During down times for the business, the existing heater would maintain the recirculation temperature of already heated water in its system. During off hours, the heat pump-assisted water heater would produce sufficient hot water to restock the system. Because the existing heater is already large enough to meet food service needs during business hours, the heat pump-assisted water heater system can be built to fit the available space, even if it is undersized.

The benefits of using a heat pump-assisted water heater are similar to those of a heat pump: improved energy efficiency and possibly lower long-term energy costs, although cost issues largely depend on the type of system being replaced. Natural gas fuel, which is used by 90 percent of food service operations for water heating, is currently cheaper than electricity in most of California.

Heat pump systems also provide cooling as a byproduct, which could be useful to counteract kitchen heat.

Heat pump-assisted water heaters are designed to address the big disadvantage of heat pump water heaters for restaurants — the longer time needed to heat the water from cold. One workaround is a much larger tank, but floor space is typically at a premium in restaurants, making this workaround unappealing for many food service operations. For a heat pump water heater to meet health department requirements, it would need a much bigger tank than its gas-fired counterpart (because the gas-fired water heater can heat water faster).

Heat pump-assisted water heaters may also be cheaper to install than a conventional, retrofitted heat pump water heater system, and the heat pump-assisted water heater does not need to meet these sizing regulations because the legacy water heater still functions as a backup system. At this point, the technology is still emerging and has not been installed commercially, but the authors estimate that initial costs for the heat pump water heater that acts as the assist, including installation, could range between $6,000 to $20,000. This amount, while significant, is still much cheaper than what it could cost a full-service restaurant to install a heat pump water heater capable of meeting water demands, which could well exceed $100,000.  

“The costs for heat pump assisted heat pumps are largely driven by the electrical work and the space required, and there may be incentives available to offset these,” Delagah said.

Another benefit is that because the heat pump-assisted water heater is a backup system, it does not require health department approval, making the process simpler.  

Both heat pump water heaters and heat pump-assisted water heaters also have the additional operational benefit of being able to benefit from time-of-use rates and the additional cooling they could provide for kitchens.

“This year in October, it was 95 degrees in the Bay Area,” Delagah said. “There are new California OSHA rules on the books for indoor temperatures — if your facilities are over an 82°F temperature indoors, you have to provide cooling centers for employees. That’s becoming an emerging concern for restaurants to meet a new heat illness standard.”

On the downside, the higher upfront costs will likely still be a significant barrier to the adoption of heat pump-assisted water heaters, even if they are relatively less expensive than heat pump water heaters.

One big hurdle is that health departments, by and large, are not familiar with the technology — and may be more resistant to its approval. The relatively high price of electricity in California, compared with gas, may be another barrier. 

Yet regulations and the need to decarbonize are moving closer, with California’s 2030 deadlines for reducing its overall greenhouse gas emissions by 40%, in comparison with 1990 levels. Restaurants are well positioned to be the public face of doing their part.

“This is great equipment for restaurants that are thinking about positioning themselves for where things are going in terms of air quality regulations,” Delagah said. “If you’re a chain restaurant, you should probably be trying this out, kicking the tires a bit, and preparing for what your solution is going to be when there is a mandate.”

To learn more about this project, read the report on the CalNEXT website, calnext.com  

About CalNEXT: CalNEXT is a statewide initiative to identify, test, and grow electric technologies and delivery methods to support California’s decarbonized future. CalNEXT is funded by the ratepayers of California investor-owned utilities and provides a means for studying emerging technologies and energy-efficiency innovations that have the potential to save energy via utility programs and/or market support.

Article written by Emily Pickrell, Energy Solutions

Commentary: Heat pump-assisted water heater technology could make big lift is an article from Energy News Network, a nonprofit news service covering the clean energy transition. If you would like to support us please make a donation.

This article is a paid promotion and the Energy News Network is not responsible for its contents.

Interest in heat pump water heater technology is rapidly growing, given its energy efficiency relative to gas-fueled equipment. For apartment building owners, especially those of large buildings, emerging heat pump technology now offers the possibility of using the stored hot water as a thermal battery, to better manage a building’s power use.

These systems, known as central heat pump water heaters, use largely the same technological approach as residential heat pump water heaters. If used to replace gas heaters in California multifamily buildings, a new study finds they could reduce greenhouse gas emissions by 1.7 million tons per year and produce $350 million in overall benefits annually from the increased efficiency of the systems, compared with gas water heaters.

The ability to use the stored hot water as a battery means that water can be heated in low-demand periods and later provided during high-consumption periods without adding demand to the grid during its highest-use period – a strategy known as load shifting.

“Load shifting is going to be really important, not just to benefit the grid, but also to ensure that these technologies provide the most cost control for the building owners,” said M M Valmiki, an energy efficiency engineer with the energy engineering consulting firm ASK Energy. “When we are electrifying buildings, especially those with really big loads like hot water for a whole building, it is important to minimize the costs of electrification, especially in comparison with natural gas.”

To better understand the benefits and challenges of using central heat pump water heaters in large multifamily buildings, researchers installed customized systems in two buildings with 120 and 135 single-room units, respectively, that house low-income senior residents in San Francisco. The results of this study can be found in the report “Commercial and Multifamily CO₂ Heat Pump Water Heater Market Study and Field Demonstration.” The study was co-led by experts at ASK Energy and Ecotope, an engineering firm focused on low-carbon building solutions, with funding from California’s emerging technology initiative, CalNEXT.

This study used central heat pump water heaters that utilize carbon dioxide refrigerants, which have the lowest global warming potential compared to other more common refrigerants on the market. Another benefit of carbon dioxide is that, unlike most refrigerants, it is not synthetic, thus avoiding environmental concerns about the impact of possible leakage.

The installations were retrofits in already occupied buildings, and a primary goal of the study was to assess the challenges involved in installing these heat pumps in existing housing stock.

Like their residential counterparts, central heat pump water heaters use refrigerants to move heat from the surrounding air to heat the water tank. Central heat pump systems need larger hot water storage tanks than natural gas-fueled systems, so they require more room than gas-fired boilers. “Heat pumps are not really that much more complicated than boilers,” said Scott Spielman, a research engineer at Ecotope and leader of the study. “It’s just that you need a bigger thermal storage system and thermal storage has costs: there’s a cost to have more water, both in the expense of the physical materials, like a storage tank, as well as in the floorspace that the tanks take up.”

For the study, the researchers considered different tank and related piping configurations to determine how to optimize the heat pump systems. For example, water heating can be done in single-pass or multi-pass stages — and tank sizing is important since oversizing can lead to lower efficiency and higher cost. Plumbing between storage tanks in the system created a challenge, because the length of time water circulates in the system impacts its temperature. These considerations and others were used to determine how to optimize thermal storage in the heat pump system as a whole.

“There haven’t been a lot of studies that show how thermal storage really operates in different, vibrant configurations,” Spielman said, noting that standardization of the design of these systems in the future will help make their installation easier and less expensive.

The research project demonstrated how the hot water storage volume could function as a thermal battery. The large volume creates the opportunity to store energy and serve as a battery. Heating water during periods of low grid demand helps to lower energy use during peak times and enhances grid reliability, especially as utilities increasingly integrate intermittent solar and wind energy into their power mix. The finding has implications for California’s grid, where concerns about additional load are sometimes used as an argument against electrification.

“Central heat pump water heaters are a much-needed way to get creative in terms of grid demand management,” said Madison Johnson, a data analyst with Ecotope, who assessed the results of the study. “By centrally managing that demand, we are not only using less electricity overall than an electric resistance system would use, but we are also able to control what time of day we would like to use that energy.”

Researchers found that access to hot water was no issue for residents, following the installation of the central heat pump water heaters, which consistently provided the 25 gallons-per-day residential demand without any issues, even during periods of load shifting.

They also found that shifting load to a lower demand time did not necessarily reduce the cost of the power to run the systems.

This result is based on the design of the test plan, which aimed to shift as much energy (that is, kilowatt-hours) out of the on-peak periods as possible. It did so successfully.

However, two issues kept the project from generating cost savings, according to Valmiki. Firstly, there were some slight increases in energy consumption outside of the peak periods. Secondly, the team did not test the controls that could reduce peak demand during those on-peak periods.

“Even though we were successful in shifting kilowatt-hours out of on-peak periods, the kilowatt demand spikes during on-peak periods were not reduced,” Valmiki said.

In a follow-up study, the researchers plan to better manage how the system triggers demand charges.

“The demand charges, in particular, are something that we will try to limit in our follow-up study since they are a large portion of utility bills for buildings that have them in their tariff,” Valmiki said.

It is still early days for central heat pump water heaters in multifamily buildings, and this study aimed to document the technology’s readiness. Seeing how the technology performs in real time is an important step, both for optimizing system design and for assessing how best to maintain the grid while increasing electrification.

To learn more about this project, read the report on the CalNEXT website. 

CalNEXT is a statewide initiative to identify, test, and grow electric technologies and delivery methods to support California’s decarbonized future. CalNEXT is funded by the ratepayers of California investor-owned utilities and provides a means for studying emerging technologies and energy-efficiency innovations that have the potential to save energy via utility programs and/or market support.

Commentary: New study identifies central heat pump water heater benefits is an article from Energy News Network, a nonprofit news service covering the clean energy transition. If you would like to support us please make a donation.