Wyoming ranks third in the nation for the carbon intensity of its electricity generation, behind only West Virginia and Kentucky. Utah ranks eighth, followed by Montana at 14th and Colorado at 16th.
Further down the list are New Mexico at 28th, Arizona at 35th and Nevada at 36th. Idaho ranks 46th, with hydropower accounting for much of its electricity generation.
Carbon intensity measures how much carbon dioxide is released for each unit of electricity generated. The state-by-state figures come from the U.S. Energy Information Administration and were compiled by U.S. Energy Data, a project from the Institute for Progress.
Robert Godby, an energy economist at the University of Wyoming, said the differences across the region largely reflect the resources states have historically relied on to generate electricity.
Wyoming, for example, remains heavily dependent on coal.
“The reason why Wyoming is so carbon-intensive is because that is the center of coal country,” Godby said.
The Powder River Basin, which stretches across parts of Wyoming and Montana, holds vast coal deposits that have historically been relatively cheap to mine. That helped make Wyoming a major electricity producer despite having the nation’s smallest population.
But there’s an important caveat to the rankings: They measure where electricity is generated, not necessarily where it is ultimately consumed.
“Coal has and still does play an important role in the national grid, and Wyoming is one of the few states where most of its power is exported,” Godby said.
That means some of the emissions counted toward Wyoming’s carbon intensity come from electricity that ultimately powers homes and businesses in other states. Wyoming is part of a regional power grid that connects it with Utah, Idaho, Oregon, Washington and California.
Nationally, electricity generation has become significantly cleaner over the past two decades. Greenhouse gas emissions from the U.S. power sector fell about 40% between 2005 and 2024 as coal plants closed and generation shifted toward natural gas and renewable energy.
Economics played a major role in that shift, Godby said. Even in coal-rich parts of the Mountain West, other sources of electricity are increasingly able to undercut coal on cost.
“What’s really killing coal on the grid is the fact that even when you have a plant available, you choose not to use it because it’s too expensive,” Godby said.
The latest data reflects that changing mix. Since 1990, every state except Idaho, Oregon and Washington has reduced the carbon intensity of its electricity generation.
Godby expects that trend to continue, even as coal remains part of the electricity mix in states such as Wyoming.
Looking ahead at a map of states shaded by the carbon intensity of their electricity generation, Godby expects one broad change.
“All the shades will be lighter,” he said.
This story was produced by the Mountain West News Bureau, a collaboration between Boise State Public Radio, Wyoming Public Media, Nevada Public Radio, KUNR in Nevada, KUNC in Northern Colorado, KANW in New Mexico, Colorado Public Radio and KJZZ in Arizona as well as NPR, with support from affiliate newsrooms across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting and Eric and Wendy Schmidt.
