The "carbon intensity" of electricity generated in the Pacific Northwest increased in 2020 compared to 2016 according to the U.S. Energy Information Administration. While 43 states produced cleaner energy, seven states, including Washington, Oregon and Idaho, emitted more pounds of heat-trapping greenhouse gases per megawatt-hour in 2020 than four years earlier. Idaho's carbon intensity increased by 7.5%, the fourth highest. The EIA attributed the increased carbon output in the Northwest to a decline in hydropower production. Wind and solar replaced some of that power, but natural gas filled most of the shortfall. Hydropower production varies from year to year based on water supply and drought interference.