Electric space heating systems and appliances like water heaters can help American homeowners reduce their energy use, and possibly their utility bills, according to a team led by researchers at Penn State.
The researchers set out to identify the most important factors driving U.S. on-site residential energy consumption, which the team said accounts for approximately 21% of primary energy consumption in the country and is more complex than commercial energy use. They found that electric heating systems like heat pumps, compared to systems that rely on natural gas and oil, had the largest impact on reducing on-site energy usage at the national and state levels. Switching to energy-efficient electric appliances could also help homeowners reduce their energy consumption, the team reported in the journal Energy Policy.
"The most surprising finding was that homes relying on natural gas for space heating were using more on-site energy compared to electric homes," said co-author Rahman Azari, associate professor of architecture at Penn State. "But it makes sense because it's an issue of heating system efficiency as well as the efficiency of appliances, and electric appliances tend to be more efficient than natural gas appliances."
Electric and gas systems have different transmission losses, but the bigger driver is equipment efficiency, said lead author Sepideh Korsavi, assistant professor of architecture at Mississippi State University who completed the work as a postdoctoral scholar at Penn State.
"Modern heat pumps often deliver two to three times more heat per unit of energy than typical gas furnaces," she said. "When you account for delivery and efficiency together, electrified systems can lower household energy use and emissions in many regions."
The researchers used the 2020 Residential Energy Consumption Survey from the U.S. Energy Information Administration to examine more than 300 determinants affecting household energy use. Published in 2023 and based on the responses of nearly 18,500 households, the survey represents the energy profiles of about 123.5 million individual homes, according to the researchers.
The team used a machine learning model, a form of artificial intelligence, to examine how the presence or absence of each determinant changed the model's performance. They removed the determinants with the least impact on the model until they had a list of 41 factors that had the greatest impact on the model and, in turn, residential energy consumption.
They found that using electricity for space heating had the largest impact on decreasing on-site household energy consumption. Other factors that decreased energy consumption included the use of electric water heaters and other energy-efficient electric appliances; the construction of multi-family buildings, like apartment complexes and row homes, whose shared walls reduce heat loss in winter and heat gain in summer; and a set thermostat temperature in winter when no one is home.
"We found that by reducing the set point temperature in winter, we can reduce energy consumption significantly," Korsavi said.
People assume that it's costly to bring down household energy usage, said co-author Lisa Iulo, professor of architecture and director of the Hamer Center for Community Design in the Penn State Stuckeman School.
"People often jump to expensive solutions like replacing windows or adding solar power to address home energy demands," she said. "That is not the place to start. Many interventions, like air sealing, changing out incandescent lightbulbs with LEDs or replacing an outdated water heater with an electric water heater - especially a hybrid one with a heat-pump boost, are lower-hanging fruit. Those incremental differences can add up to big overall energy savings and lower utility bills. Long-term affordability is important to homeowners and in the work we're doing."
Mehrdad Mahdavi, the Dorothy Quiggle Career Development Assistant Professor of Computer Science and Engineering at Penn State, also contributed to this work. The Penn State Hamer Center for Community Design and its Resource and Energy Efficiency Lab, the College of Art & Architecture's Stuckeman Center for Design Computing and Penn State's Institute of Energy and the Environment supported this research.
