Xcel Energy is seeking a 6.1 percent increase in rates for its Wisconsin electric customers, including those in Hudson, Eau Claire and La Crosse.

The request, announced Friday, would be Xcel’s fourth consecutive, and largest, rate hike in that state since 2009, and would take effect next January if approved by the state Public Service Commission.

The utility, based in Minneapolis, serves 251,000 electric customers in more than 200 communities in western and northwestern Wisconsin and Michigan’s Upper Peninsula.

In Minnesota, Xcel is seeking a rate hike of more than $200 million, or roughly 8 percent. That case, pending since last year, has twice been scaled back from a larger request and interim rate hike for its 1.2 million Minnesota customers. It is pending before the Minnesota Public Utilities Commission.

The company said the $40 million boost in Wisconsin electric rates is needed to cover investments in generation, including upgrades to its Minnesota nuclear power plants, transmission lines and distribution facilities and to cover increased operating costs.

Xcel also said it wants a 3.8 percent, or $4.7 million, increase in rates for its Wisconsin gas customers. Most of that increase would cover costs of environmental cleanup at a former manufactured gas plant that operated at the turn of the 20th century on Ashland, Wis., property later acquired by Xcel.

In a regulatory filing, Donald Reck, regional vice president of rates and regulatory affairs, said Xcel plans to invest $1.1 billion over the next five years in its Wisconsin-Michigan region, more than half of it on electrical transmission projects.

Xcel said it seeks a return on equity of 10.4 percent, an equity ratio of 52.5 percent, from its Wisconsin operations.