As states and local communities push to electrify heating systems in buildings, the use of smart thermostats could inadvertently strain power grids in the morning before solar energy is available, researchers at Cornell University found in a newly published study.

About 40% of U.S. households now have smart thermostats, after utilities began deploying the technology more than a decade ago to better match energy consumption with supplies, according to the study published in the journal Applied Energy.

Consumers can use the technology to manage their power bills and consumption through the day and to take advantage of demand response opportunities and other energy savings incentives. Power companies monitor electricity use in real time and try to manage outages more effectively, keeping their grids more stable.

But as more people install electric heat pumps for home heating, thousands of smart thermostats in a single city can inadvertently work in tandem after being programmed by their algorithms to automatically turn up the heat before people wake up. That causes consumption of power to peak when renewable energy is scarce, requiring the dispatch of fossil fuel-powered generation.

This, in turn, can hinder integration of renewables into the grid and undermine greenhouse gas reduction efforts in states such as New York, which is looking to electrification to meet its ambitious clean energy goals, the study said.

Out of sync with solar

The Cornell researchers used data from 2,200 New York customers of ecobee Inc., a Canadian smart thermostat and home energy management company whose customers can opt to share their power use data.

The researchers learned that average energy use among those New York homes rose 40% around 6:05 am, an hour before daylight.

"All of a sudden, there's a huge demand for electricity and that demand has to be managed by something," said Zachary Lee, a recent Cornell Ph.D. graduate who co-authored the study with Max Zhang, a professor at the university's Sibley School of Mechanical and Aerospace Engineering. "It means dispatching controllable generation, like natural gas or some more fossil fuel-based generation."

Because such a large share of carbon emissions in cold-weather states such as New York come from heating, it is critical for policymakers to consider how electric appliances like heat pumps will affect the grid once they are ubiquitous, Lee said.

"We saw this new data set that [offered] a very granular look at how people actually use heating systems in homes," Lee said. "We wanted to take a more detailed look so energy planning and policy can be better informed in the future."

States with more air conditioning than heating needs also experience power demand peaks that can be difficult to manage. But from a climate perspective, it is critical to solve the relationship between smart thermostats and heating because those energy loads are higher at a time when solar energy is scarce, Lee said.

Wind energy could bridge the gap

Although the idea behind smart thermostats is to give homeowners more control over their energy consumption, one solution for utilities and regulators could be to use incentives that spread out energy use for heating over time, the researchers wrote. More consumer education and attractive financial rewards could encourage customers to relinquish some of their thermostat independence.

Another solution is to look more closely at heating electrification when planning renewable and energy storage resources.

"The highest heating demand periods also have the highest average 100-meter wind speed, suggesting that wind generation could be very effective at supplying renewable electricity during high heating demand times," the study said.

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