MidAmerican Energy Co. has filed plans with the Iowa Utilities Board to develop up to 552 megawatts of new wind energy generation in Iowa, another in a string of large additions.

MidAmerican plans wind farms at two new undisclosed sites, where the company is still completing negotiations. Construction is expected to be started in the spring and should be done by the end of 2016.

Bill Fehrman, president and CEO of MidAmerican Energy, said the company continues to focus on developing wind projects because wind generation offers many clear benefits for its customers. “Wind continues to be a factor in keeping our customers’ electricity rates among the lowest in the nation,” he said in a statement.

Gov. Terry Branstad noted that Iowa derives a greater percentage of its electricity from wind than any other state, and is second in the nation in the number of people employed in the wind industry. “Thanks to our low electricity prices and commitment to renewable energy, major tech companies and other energy-intensive businesses are interested in locating and expanding facilities here, which is good economic news for all Iowans,” Branstad said.

Increasing the company’s investment in wind turbines gives MidAmerican the ability to reduce its reliance on coal, which helps protect customers from rising costs associated with meeting stricter environmental standards, Fehrman said. The company is on track to have 57 percent of its total retail load come from wind energy.

Since 2004, MidAmerican has invested approximately $5.8 billion building wind projects in Iowa. With the addition of the two projects announced today, MidAmerican’s wind assets will include about 2,000 turbines, more than 4,000 megawatts of wind generation capacity and a total investment of about $6.7 billion.