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A growing portion of Americans who are struggling to pay for their household energy live in the South and Southwest, reflecting a climate-driven shift away from heating needs and toward air conditioning use, an MIT study finds.

The newly published research also reveals that a major U.S. federal program that provides energy subsidies to households, by assigning block grants to states, does not yet fully match these recent trends.

The work evaluates the "energy burden" on households, which reflects the percentage of income needed to pay for energy necessities, from 2015 to 2020. Households with an energy burden greater than 6% of income are considered to be in "energy poverty."

With climate change, rising temperatures are expected to add financial stress in the South, where air conditioning is increasingly needed. Meanwhile, milder winters are expected to reduce heating costs in some colder regions.

"From 2015 to 2020, there is an increase in burden generally, and you do also see this southern shift," says Christopher Knittel, an MIT energy economist and co-author of a new paper detailing the study's results. About federal aid, he adds, "When you compare the distribution of the energy burden to where the money is going, it's not aligned too well."

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