That isn't to say the utility would never consider building one in Utah. "If our objective as a society is to move away from carbon-emitting resources, probably we'll have to consider nuclear in some form" eventually, he said.

PacifiCorp's decision not to add more coal-burning plants in Utah might involve the need to sell power from its grid to California, which is among the states it serves. California officials recently said they would not consider purchasing electricity produced by new coal plants unless the plants met an extremely strict limit: no more carbon dioxide released than is emitted by gas-fired plants.

Eskelsen said PacifiCorp wants to make sure regulators are inclined to approve the type of generating that the company does. "It's one of the reasons why in our current resource procurement initiative, we've removed the coal options," he said. The company is concerned that "if we were to build a coal-fueled project and then there would be an extensive carbon tax of one kind or another, either imposed by the state or federal government, that would make the project no longer 'least-cost, least-risk,'" he said.

"Least-cost, least-risk" is a standard required by utility regulators in the states PacifiCorp serves. If a plant is built that is considered outside the range of reasonableness, "we're subject to regulatory disallowance," he said. PacifiCorp could find itself docked by regulators.

"It kind of pushes us toward natural gas projects and wind power."

Rocky Mountain Power has several natural gas-powered generating stations in Utah. Two of the most recently built are near Mona, Juab County, and Vineyard. They can generate 520 megawatts to 569 megawatts, depending on weather conditions, he said. The Gadsby Plant on North Temple, capacity 235 megawatts, was converted from coal to natural gas in the early 1990s. Three additional combustion turbines completed in 2002 have a combined output of 120 megawatts, Eskelsen said.

Rocky Mountain Power leases 200 megawatts from the West Valley plant, another gas-fired station, he said.

Natural gas for the plants comes from a variety of sources, much of it piped from oil and gas fields in Wyoming. But where does Rocky Mountain Power find that other source Eskelsen mentioned, wind power?

Wind power

"Because we have an integrated system across our six-state service area ... our generating resources are used by customers in all six states," said Jeff Hymas, another spokesman for Rocky Mountain Power. "So, for example, wind farms that we build in Wyoming serve customers in other states as well as Wyoming." Utah is among them.