A worker walks down stairs next to the nose of a Boeing 737-800 airplane being assembled Tuesday, Dec. 16, 2014, at Boeing's 737 facility in Renton, Wash. Boeing and Puget Sound Energy announced Tuesday that Boeing plans to switch to using all-renewable energy at the factory, by buying more wind power credits and continuing to use hydropower. (AP Photo/Ted S. Warren)

Boeing said Tuesday it plans to buy renewable energy credits to replace fossil-fuel power at the factory in Washington state where it assembles its 737 commercial airplanes.

The aerospace company and the utility, Puget Sound Energy, said the plan will move the Renton factory near Seattle toward an all-renewable energy mix.

Boeing Co. says it will offset electricity from coal and other fuels by paying a premium to buy wind power credits tied to the Bellevue-based utility's Wild Horse Wind and Solar Facility near Ellensburg.

The utility's energy mix in 2013 was about 50 percent hydro, wind and other renewable sources, according to state figures. Natural gas and coal made up the other half, and that's the portion Boeing plans to replace with renewable energy credits.

"It will cost us a little more in the short term. We think the investment makes sense for the environment, our employees and the community," said Beverly Wyse, vice president and general manager of the 737 program.

Boeing officials declined to say how much more they're paying, or how much energy the factory uses. Boeing assembles 42 planes a month at the Renton site, which includes about 4.3 million square feet of building space.

Energy produced in the region from multiple sources gets pooled to the regional grid, so it's difficult to track the source of a particular electron that ends up being used at a home or a business. So Boeing may still technically get some coal-fired electricity to that plant.

Boeing 737-800 airplanes are on the assembly line Tuesday, Dec. 16, 2014, at Boeing's 737 assembly facility in Renton, Wash. Boeing and Puget Sound Energy announced Tuesday that Boeing plans to switch to using all-renewable energy at the factory, by buying more wind power credits and continuing to use hydropower. (AP Photo/Ted S. Warren)

"You can't direct an electron to any one location. It goes to the power pool," said Heather Mulligan with the utility. Renewable energy credits "are a way to basically put some ownership on that green electron at the point of use."

Marc Krasnowsky, a spokesman for NW Energy Coalition that has pushed for more renewable energy use, praised the company for looking at becoming all-renewable.

"They're basically turning their fossil power green, and that's laudable," he said.

  • Jason Teller, vice president of customer solutions for Puget Sound Energy, stands next to a model of a wind turbine as he talks to reporters Tuesday, Dec. 16, 2014, at Boeing Commercial Airplanes' 737 assembly facility in Renton, Wash. Boeing and Puget Sound Energy announced Tuesday that Boeing plans to switch to using all-renewable energy at the factory, by buying more wind power credits and continuing to use hydropower. (AP Photo/Ted S. Warren)

  • A sign indicates that power is turned on Tuesday, Dec. 16, 2014, at Boeing's 737 assembly facility in Renton, Wash. Boeing and Puget Sound Energy announced Tuesday that Boeing plans to switch to using all-renewable energy at the factory, by buying more wind power credits and continuing to use hydropower. (AP Photo/Ted S. Warren)

  • Boeing 737-800 airplanes are on the assembly line Tuesday, Dec. 16, 2014, at Boeing's 737 assembly facility in Renton, Wash. Boeing and Puget Sound Energy announced Tuesday that Boeing plans to switch to using all-renewable energy at the factory, by buying more wind power credits and continuing to use hydropower. (AP Photo/Ted S. Warren)

  • Beverly Wyse, vice president and general manager of Boeing Commercial Airplanes' 737 program, stands next to a model of a wind turbine as she talks to reporters Tuesday, Dec. 16, 2014, at Boeing's 737 assembly facility in Renton, Wash. Boeing and Puget Sound Energy announced Tuesday that Boeing plans to switch to using all-renewable energy at the factory, by buying more wind power credits and continuing to use hydropower. (AP Photo/Ted S. Warren)

  • This undated photo provided by Boeing Commercial Airplanes shows Puget Sound Energy's Wild Horse Wind & Solar Facility near Ellensburg, Wash. Boeing and Puget Sound Energy announced Tuesday that Boeing plans to switch to using all-renewable energy at their 737 assembly facility in Renton, Wash., by buying more wind power credits and continuing to use hydropower. (AP Photo/Courtesy Boeing Commercial Airplanes)