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Wyoming wind will be powering more Utah homes by 2021, Rocky Mountain Power announced Tuesday.

The state's largest provider of electricity said it plans to build a $3.5 billion wind generation and transmission project in southwestern Wyoming over the next three years. The 1,100 megawatt facility will increase the utility's total generation capacity by 10 percent, company officials said.

Construction of the roughly 440 wind turbines will be accompanied by a 140-mile transmission line to be built between the Jim Bridger power plant in southwestern Wyoming and Medicine Bow, Wyoming, connecting the turbine array to the company's greater electrical network.

Rocky Mountain Power company spokesman David Eskelsen said that although the company will not immediately need the additional wind capacity, it has chosen to build the project now to take advantage of federal tax credits that only apply to wind projects built before 2020.

Assuming no other changes to the utility's portfolio of energy sources, wind power would account for nearly one-quarter of Rocky Mountain Power's generation capacity when the Wyoming project comes online.

PacifiCorp operates as Rocky Mountain Power in Utah, Idaho and Wyoming and as Pacific Power in Oregon, Washington and California. Utahns purchase about 44 percent of the electricity sold by PacifiCorp, according to the company.

Currently, wind power represents 15 percent of the utility's total 10,900 megawatt capacity. Coal-fired power plants represent a little less than half — 45 percent — of that capacity. Solar power generation power is about one percent.

Technological advancements have helped make wind power more cost-effective for the company, said Chad Teply, vice president of Strategy and Development for PacifiCorp.

In addition to the new construction, Rocky Mountain Power plans to update its existing wind turbines with longer blades, modern generators and other new technologies. The upgrades will increase each turbine's production by about 20 percent and extend their projected life by a decade.

The overall project, though costly initially, will actually result in cost savings, Teply said.

Gary Hoogeveen, senior vice president of Rocky Mountain Power, said the company has no plans to change base electrical rates for customers in the near future.

But building more wind turbines will further the company's goal of diversifying its energy mix, Eskelsen said. The more energy sources the company has in its portfolio, the better it can protect customers from rate hikes associated with fuel shortages or other market circumstances.

"A more diverse resource mix is more secure for customers in the long run," he said.

The company's long-range plans, submitted to state regulators for review on Tuesday, also call for the construction of more than 1,000 megawatts of commercial solar generation, 77 percent of which is projected to be built in Utah.

The company does not plan to begin retiring any of its existing coal plants until 2030.

"We are decarbonizing our fleet," Hoogeveen said. "But we have to do that at a measured pace with the power plants that already exist."

Environmental advocacy group HEAL Utah said Rocky Mountain Power was not moving away from coal power fast enough.

"The public repeatedly says it wants to move urgently to clean energy," said Matt Pacenza, HEAL Utah's executive director. "Yet Rocky Mountain Power's plan would force its customers to buy dirty, dangerous, and more expensive coal power from its Utah plants for at least 20 to 30 years longer."

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