PNNL

Every summer, grid operators brace themselves for an increase in energy demand as people turn their air conditioners on. This makes summer a “peaking season” in many parts of the United States. Grid operators can generally predict and prepare for peaking energy demands and make sure enough is available from fossil fuels, nuclear power, and renewable sources. 

Once unique to summer, now utilities have begun to note that energy demand sometimes reaches all-time highs in particularly cold winters, like Texas’s 2021 winter storm. 

As more people switch from fossil-fuel heating to electric, grid researchers and utilities are now faced with a question: can the power grid support peak demands in winter?

In a new paper, researchers from the Department of Energy’s Pacific Northwest National Laboratory (PNNL) and North Carolina State University (NCSU) teamed up to explore this question by modeling how a wide adoption of electric heat pumps would affect the power grid. In their modeling, they also incorporated the potential future effects of climate change. As a case study, the team used Texas’s independent power grid, the Electric Reliability Council of Texas (ERCOT). 

The researchers found that should residential buildings in Texas go all electric for heating, high- and ultra-high-efficiency heat pumps would ease electricity demand pressure on the grid in both extreme winter and summer temperatures, compared to scenarios where low-efficiency alternatives were broadly adopted. Heat pumps are vastly more energy efficient than other heating systems, including others that run on electricity. In the long run, switching to more efficient electric heating and cooling could lower energy bills for consumers along with lowering carbon emissions.

The results suggest that predicting future peak demand needs to account for a changing climate as well as changing technologies and related policies, said Henry Ssembatya, a PhD student at NCSU. With the electrification of heating, it’s important to understand what heating systems can support a reliable power grid. 

“So far, no one has thoroughly looked at the combined effects on today’s grid of climate change and the power demand from heat pumps in the winter,” said Casey Burleyson, an Earth scientist at PNNL and coauthor on the paper, which was published in Earth’s Future in June. “Our goal with this research is to help inform grid planners as they think about the future.” 

Modeling energy demand in Texas

Currently, around 60% of Texas households use electric heating such as electric furnaces or baseboard heaters. But what if the remaining 40% of households (those that currently use non-electric heating) switched to using an electric heat pump? Ssembatya and his colleagues modeled the energy demand of three different electrification scenarios: one with 100% electrification via adoption of standard heat pumps, one with adoption of high-efficiency heat pumps, and one with adoption of ultra-high-efficiency heat pumps. They also included a base case that represents today’s level of electrified heating.

The researchers found that wide adoption of standard-efficiency heat pumps would reduce load in the summer due to their higher efficiency compared to other types of air conditioning, but they might strain ERCOT’s systems in the case of a rare but extreme winter storm. High- and ultra-high-efficiency heat pumps, however, ease that strain and significantly lower the risk of winter outages, Ssembatya said. 

Better cold-weather heat pumps on the way

DOE is currently working with industry partners to improve cold-weather heat pumps, which have historically been less effective at extremely low temperatures. Last month, DOE announced that the eight manufacturers in its Residential Cold Climate Heat Pump Challenge successfully produced heat pumps that operate efficiently at temperatures as low as 5 degrees Fahrenheit (–15 degrees Celsius). The agency is now working with industry partners to improve the energy efficiency and performance of rooftop heat pumps for commercial buildings.

In the summer, heat pumps’ energy efficiency would still decrease the overall load on the grid, Ssembatya said. And with climate models showing a general rise in temperature over the coming century, heat pumps will be necessary to both decrease carbon emissions and increase cooling efficiency.

"By 2060, temperatures might be so high that cold snaps might become a lesser issue, though there is more uncertainty about occurrence of cold snaps in the future. Overall, we see that more efficient heat pumps mitigate the worst effects of both severe heat waves and cold snaps on the grid," Ssembatya said.