About 31 percent of U.S. households faced difficulties in paying energy bills or meeting their heating or air conditioning needs in 2015, a year when overall energy-related spending was the lowest in more than a decade, according to a Sept. 19 report from the U.S. Energy Information Administration. The statistics from the agency’s most recent residential energy consumption survey reported that about 25 million households, or one in five, said they went without or cut back on necessities like food and medicine to pay their energy bills. The survey found that 14 percent of households received disconnection notices while 11 percent kept their homes at unhealthy or unsafe temperature. The agency said differences across geographic regions and between urban and rural residents was meager. Energy affordability is largely associated with the structural features of a residential building and socioeconomic characteristics, the agency said.