The Little-Known Power of Circulator Pumps

Authored in collaboration with Ashley Leung.

Which uses more electricity: washing your hands or powering your refrigerator? It could be the former in many places—surprisingly, some of the biggest energy users in our buildings are the pumps that circulate hot water. In fact, many of them more than double the amount of energy used to heat that water in the first place and use as much electricity as two typical refrigerators, according to research from Energy Solutions.

iStock/patanasak

Hot water circulator pumps are powerful for water conservation, saving as much as 1000 gallons per person annually. Without these pumps, someone would typically need to leave their tap running for a while and wait for hot water from the heater to make its way through the pipes—that means a lot of otherwise useable cool water is going straight down the drain. Circulator pumps move hot water in pipes around the building so that it’s ready to use faster, limiting the need to run the tap and therefore saving a lot of water, time, and money.

Not All Pumps Are Created Equal

The most common circulator pumps run all day, every day, whether you’re actively using hot water or not. This causes a lot of heat to dissipate in the pipes 24/7 and requires the water heater to work twice as hard to keep the water hot. And operating the pump continuously also uses a lot of electricity, in fact more than two typical refrigerators on an annual basis, according to a recent report from Energy Solutions. The combined energy use for water heating and pump operation makes these circulators some of the largest energy hogs in homes and buildings that use them.

Some circulator pumps use a timer that can be programmed to only run the pump at certain times of day, but those still typically run 12 to 16 hours per day, so they are only marginal improvements. Thankfully we have other much more efficient models that save as much water while using only a small fraction of the energy. These options might, for example, pump on demand when hot water is needed or use other advanced control solutions in large apartment buildings.

These smarter circulators would save you more money on your energy bill, to add to the water bill savings. In fact, those energy and water savings pay back for the cost of the pumps within 2 to 6 years, according to Energy Solutions—that is a lot considering circulator pumps can last for decades.

In addition, continuous and timer-controlled pumps are a barrier to moving off fossil fuels for domestic water heating, because they cause heat pump water heaters, the clean alternative to gas water heaters, to run in inefficient electric resistance mode much more frequently than they typically do. As a part of their electrification efforts, utilities and states across the country are seeking to put more heat pump water heaters in buildings through incentives and building codes. Continuous and timer-controlled pumps are a hindrance to these efforts as they need to be replaced when installing a heat pump water heater, increasing the cost of the conversion.

The Policies of Circulator Pumps

The Department of Energy (DOE) has been working since 2016 to develop an energy efficiency standard for hot water circulator pumps. However, this effort only looks at a small piece of the energy- saving and decarbonization opportunity. Making the motor more efficient only saves a limited fraction of their energy use.

The big opportunity for energy and carbon savings is in moving from continuous and timer-controlled pumps to on-demand and other advanced control strategies. These can save nearly 90% of the electric energy, more than half of the water heating energy, and remove a barrier to the cost-effective electrification of water heating, according to Energy Solutions. And this is the type of transformative opportunity we need to pursue if we want to seriously cut down on energy waste, reduce emissions, and avert the climate crisis.

One of the promising policies for transitioning from wasteful conventional circulator pumps to smart and efficient alternatives, is through flexible demand appliance standards that California initiated with Senate Bill (SB) 49 in 2019. These standards are relevant to circulator pumps because these pumps lend themselves particularly well to the use of controls to shift demand away from peak electric demand periods, while also cutting pollution from reduced gas combustion.

One of the Largest Standard Opportunities

Implementing a standard under SB 49 authority for on-demand or other advanced control solutions for domestic hot water circulation pumps would save a lot of electricity for pump operation and gas for water heating. Researchers found that, between now and 2030, this could save Californians 5 million metric tons of CO2 and 7 terawatt-hours of electricity (equivalent to taking 1 million cars off the road for one year). It would also cut down on 500 to 800 million therms of methane (taking another 500,000 to 800,000 cars off the road for one year). This standard would be one of the largest and most cost-effective appliance standard opportunity to help achieve AB 3232’s goal of reducing emissions associated with energy use in buildings by 40 percent by 2030.

Smart and Efficient Circulator Pumps for All

On-demand controls work well for single-family homes. For large apartment buildings with central hot water systems, where circulator pumps are prevalent because of the longer pipe lengths and hot water wait times, more advanced control solutions are needed, such as thermally balanced variable speed pumps. These applications are particularly important from an equity perspective because a disproportionate share of low-income households live in apartments where inefficient circulator pumps contribute significantly to their energy burden.

In addition to the higher relative costs of energy waste, low-income households are often less able to access the benefits of newer, more efficient products that save money for those who can afford the upfront costs. They are often renters with no control over equipment choices such as circulator pumps. Standards are one of the best ways to ensure that low-income households are not left behind and have equitable access to energy efficiency and decarbonization benefits.

Saving Money and the Planet

Increasing energy efficiency and cutting climate pollution with technologies like smart and efficient circulator pumps help us to better integrate renewable energy onto the grid and can even lower the cost of electricity. They can save us all money on utility bills while also paying for themselves in savings, conserving energy and water, slashing emissions and decarbonizing our buildings in the face of the climate crisis. Our decision-makers must combine policy levers such as SB 49 with technology solutions like efficient hot water recirculation pumps to set us on the ambitious, yet necessary path forward to meet science-based climate targets and preserve a livable planet.

About the Authors

Pierre Delforge

Senior Scientist, Building Decarbonization, Climate & Clean Energy Program

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