How to reduce winter grid peaks from behind the meter

Weatherization, heat pumps and flexible loads could prevent Texas-style disasters, cutting peaker-plant and in-home carbon emissions to boot.

Image credit: Tracy Adams
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Summer isn’t the only season driving power grids to their limits anymore. February’s grid disaster in Texas proved that. And in future decades, efforts to shift homes and businesses from fossil-fueled to electric heating could raise winter grid stresses across broad swaths of the country, from the Southeast to the Upper Midwest and New England.

This is a new challenge for utilities and grid operators accustomed to managing air-conditioning-driven summer grid peaks. But investing in efficiency and grid flexibility could help reduce reliance on carbon-emitting peaker plants during cold snaps, while also tackling some of the country’s heaviest behind-the-meter carbon emissions as well.

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These findings emerge from two sources of data released over the past week. The first is a new report from the American Council for an Energy-Efficient Economy (ACEEE), which details how a combination of efficiency measures and grid-responsive technologies can yield major reductions in winter electricity demand.

The second comes from New York residential efficiency provider Sealed, which has compiled data mapping showing that household carbon-emission profiles are much higher in winter than in summer — a discrepancy it’s working on reducing through projects that include the foundational technologies that ACEEE’s report cites.

Multiple packages to lower winter loads

Let’s start with ACEEE’s report. It highlights how winter cold snaps can restrict the supply of electricity from fossil-fueled power plants, causing shortfalls even when electricity demand doesn’t spike as high as it normally does in summer. That’s what happened in Texas this winter — and the result was days-long power outages and loss of life.”

Northern climes face even longer cold spells on a regular basis, so these regions have taken more steps than Texas has to cold-proof their energy infrastructure. But as the country shifts to electric vehicles and heating as part of decarbonization efforts, those winter loads can be expected to grow well beyond their present peaks, according to forecasts from the National Renewable Energy Laboratory’s Electrification Futures Study.

Graphic source: ACEEE

Building more generation and grid capacity to meet those rare peaks is one way to deal with them. Another approach could be to reduce the peaks at their source.

To test the second option, ACEEE modeled a four-day cold snap under a 2040 high-electrification” scenario matching the carbon-cutting goals of New England states. It then tried out a range of demand-side management (DSM) investments across portions of the region’s residential and commercial buildings.

The standard DSM” package — standard insulation and air-sealing measures, plus replacing oil- or gas-fired furnaces or older resistance electric heaters with the latest generation of cold-climate air source heat pumps — can reduce overall peak load by 7 percent, according to ACEEE’s analysis. These relatively low-tech efficiency improvements represent what ACEEE expects to see by 2040 under best-in-class” energy efficiency mandates like those in place in Vermont and Massachusetts.

Graphic source: ACEEE

The smart DSM” package adds connectivity, flexibility and load intelligence” to that standard package, with smart thermostats to shift heating loads from times of higher to lower grid demand, and space and water heaters that can be controlled by utilities to shed load at times of peak grid stress. Those variables yielded a 12 percent reduction in peak demand and 23 percent greater energy savings than the standard package over the four-day period.

Graphic source: ACEEE

The deep DSM” scenario — an ambitious but plausible” combination of deep building retrofits with rooftop solar, batteries and electric vehicles that can shift load — shaved peak demand by 38 percent and resulted in nearly quadruple the energy savings of the standard package over the four-day period.

Graphic source: ACEEE

ACEEE recommends that state regulators order utilities to predict and plan for winter peaks and promote weatherization and retrofit programs to roll out these technologies to a wide set of customers.

We wouldn’t want utilities to have to build new power plants that are often dirtier and more expensive, and if we get this right, they won’t have to,” said Mike Specian, the report’s lead author and ACEEE utilities program manager.

These types of programs don’t have to be a financial burden on utilities, the report says. All but the most intensive retrofits come in at lower cost per kilowatt-hour than the average cost of wholesale electricity during winter peak demand events — and that’s not counting the benefits from carbon reduction and health gains that stem from replacing oil- and gas-burning heaters with electric heat pumps, according to the report.

Cutting the most carbon-intensive energy demand in homes

That brings us to our second set of data, from Sealed, a New York-based startup that finances the upfront cost of energy retrofits through monthly payments taken out of homeowners’ energy savings. The two most effective options for most customers in its home state market — weatherization and air-source heat pumps — are more or less identical to ACEEE’s standard demand-side management package and save considerable money over the long run, despite their high upfront cost, CEO Lauren Salz said.

But data compiled from federal and state data sources shows these are also the most effective ways to reduce a home’s carbon emissions, she said. The simple reason is that air conditioning uses electricity, whereas much of the country burns fossil fuels to provide heat.

According to Sealed’s analysis, residential air-conditioning loads contributed less than 1 ton of carbon-dioxide emissions per household on average over the course of a year. But the same homes in northern climate regions can emit anywhere from 3 tons to as much as 15 tons of CO2 from heating.

Graphic source: Sealed

When it comes to regional differences in emissions from heating, Salz says that home size matters a bit, but how old homes are and what fuel they use matter the most.” Homes in the Northeast tend to be smaller than the national average, for example, but also tend to be older and use heating oil, which is more carbon-intensive than natural gas. Rural areas that use propane for home heating also have high emissions profiles.

To cut carbon emissions from these heating hot spots, you need weatherization, you need electrification, and you need to get onto renewables” to supply the new electricity loads, she said. That’s the same point being made by electrification advocates in California, Massachusetts and a handful of other states.

At the same time, you can’t just do electrification on its own, as the ACEEE report points out, because then you’ll have a demand problem during the wintertime.” Failing to make all-electric homes more efficient can create spikes in customers’ electric bills — and if there’s one thing that has proven to stymie well-intentioned policies aimed at achieving mass-market buy-in, she said, it’s failing to make it as easy and affordable as possible.”

(Article image courtesy of Tracy Adams)

Jeff St. John is the editor-in-chief of Canary Media. He covers the technology, economic and regulatory issues influencing the global transition to low-carbon energy. He served as managing editor and senior grid edge editor of Greentech Media.