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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.

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

Home electrification has many benefits: it is cleaner, more efficient, and reduces environmental degradation.

It also means that existing infrastructure for managing power coming into homes may need to be rethought. When customers want to switch from gas to electric appliances or add an electric vehicle charger to their home for example, many customers are faced with having to upgrade their electric service. This is an expensive project, and many customers may decide not to electrify. Fortunately, some emerging technologies in the California market are designed to intentionally balance a home’s power usage, and allow homeowners to avoid expensive panel upgrades, making electrification a workable option in situations when electrical upgrade costs or local infrastructure shortfalls would otherwise put a stop to the project.

These devices are known as “intelligent power management technologies” or IPMTs. They give customers options to juggle the use of different appliances and their power requirements to avoid capacity constraints and reduce installation costs when looking to fully electrify their homes.

They also have a much broader importance: helping the utilities manage and reduce the impact of millions of additional heat pumps, electric vehicles (EVs), and other smart appliances that California expects to add to the grid. The additional expected load is not insignificant. For example, California plans to have more than 12 million EVs on the road by 2035.

“These (IPMT) technologies are a real opportunity for utilities in California,” said Nick Neverisky, manager of Consumer Insights at VEIC and one of the authors of a CalNEXT report on alternative technologies that can mitigate the need for an expensive panel upgrade. For utilities, the technologies could make it easier for customers to participate in energy efficiency and demand response programs. It will be welcome help, said Neverisky, noting that “as California moves to rapidly electrify, the state will run into capacity constraints on a grid level, on a neighborhood level, and on a household level.”

With funding from CalNEXT — California’s emerging technology initiative — the VEIC team, with support of the Ortiz Group, recently published a report, “Market Study of Household Electric Infrastructure Upgrade Alternatives for Electrification”. This report looks at four alternative technologies and how each could be used to reduce the overall grid demand, both on a customer and a utility level.

“These technologies can help manage that capacity issue on a larger scale,” Neverisky said, noting that reducing the power demand helps utilities avoid the need for additional distribution infrastructure.

The study included smart technologies in the following four categories: outlet splitters, smart circuit breakers and relays, circuit control units, and smart electric panels.

The outlet splitter is the most basic technology. It is a circuit-sharing switch that splits an outlet between two loads, while preventing them from both drawing power at the same time. It’s designed to control power draw when two major electric devices are in the same room and can share a circuit, such as an EV charger and a clothes dryer both located in a garage.

A big advantage of the outlet splitter is that it does not require professional installation or configuration to meet code requirements. It’s a solution that could be easily utilized by a homeowner or resident. Its low cost and portability make it a good option for rental units.

A circuit control unit is another more comprehensive smart technology option. This is a stand-alone load management device that prevents a device from operating depending on available power on a circuit.

“Let’s say your electrical panel doesn’t have enough space to put in another circuit for the electric car charger,” said Alex Pine, an energy consultant with VEIC and a co-author of the report. “The electrician installs one of these circuit control devices on an existing circuit, for example an electric stove. This allows the stove and electric car charger to share the same existing circuit. When you get home, you plug in the car and the car starts charging. When you start cooking, the car charger shuts off, then resumes as soon as you are done.”

It’s best suited for a low-priority system and a high-priority system, or for two systems (such as heating and air conditioning) that will not run at the same time.

“They’re inexpensive, and they’re very easy to install for a hardwired device,” Pine said. “These circuit control units can be used in an application where the homeowner or resident is looking to add one new electric load and need a simple solution.”

A potential future option currently under development is a smart circuit breaker. A smart circuit breaker provides the same overcurrent protection as a conventional circuit breaker and installs in a conventional circuit breaker panel. Smart circuit breakers, however, can also collect electrical system usage data and control the circuit they are installed on. Smart circuit breakers are currently on the market but at the time of the report did not offer intelligent power management.

When they are on the market, these features could open the door to power management that is scalable, allowing a customer to juggle power between individual circuits in their circuit breaker panel. This is especially important for houses where a range of additional electrical equipment is being added.

A smart panel is the broadest solution. A smart panel fully replaces a traditional electric panel and is fully integrated into the functionality of the home. It typically allows for control, monitoring, and management of all circuits within the house, with features such as energy consumption monitoring and remote access capabilities. It allows customers to better understand how and when they use electricity, which may encourage them to reduce energy consumption overall and/or shift energy consumption to off-peak hours for customers on time-of-use rates. As a smart panel manages all circuits in a building, there is more flexibility in managing circuits including smaller capacity ones.

One big challenge for all these technologies is getting the word out — to customers who would benefit by being able to afford the upfront cost of electrification, to utilities that could benefit from customers managing their increased electricity demand right at the source, and to contractors and electricians, who are key in facilitating their adoption in homes.

“Demonstrating how IPMTs can help homeowners achieve their energy goals, whether electrification or savings, is necessary to gaining customer support for these technologies,” the authors wrote in the report.

Customer buy-in, the authors emphasize, will greatly help California meet its ambitious carbon reduction goals.

“We’ve got older homes that don’t have as much capacity, with residents who do not have the income to afford to retrofit service upgrades,” Neverisky said. “If we want to continue to decarbonize, and do so equitably, these smart technologies are going to be part of the solution.”

As utility customers consider switching out old appliances to cleaner electricity in their homes or adding EV chargers to their garages, these technologies offer a bridge to overcome the first-cost barrier and help facilitate success. Utility incentives could entice customers and give them the confidence boost they need to make the decision to go electric and be a part of the solution to decarbonize California.

To learn more about this project, read the report on the CalNEXT website, or email info@calnext.com to continue the discussion.

Written by Emily Pickrell, this article was submitted by 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. 

Commentary: Smart panel technology may replace need for pricey upgrades 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.