TOPEKA, Kan. — The Kansas Corporation Commission on Thursday formally approved Westar Energy’s rate increase request, signing off on a $30.7 million September settlement.

Regulators announced the unanimous approval of the settlement, which brokered by Westar officials, KCC staff and the Citizens’ Utility Ratepayer Board. The increases in electric utility bills will take effect Dec. 1.

Westar applied for the rate increase mostly to pay for required environmental upgrades at its La Cygne power plant in eastern Kansas. The settlement did not include Westar’s proposal to shift about $50 million of cost from its large industrial and commercial customers to residential and small-business ratepayers.

Under the settlement, residential customers will get the biggest increase, $18 million, followed by small businesses with a $12.7 million increase. Medium-sized business rates would go up $3.9 million; large industrial customers will pay $3.2 million; cities and other street lighting customers, $2.1 million, and school districts, $500,000.

The KCC estimated that residential customers who use an average of 900 kilowatt hours per month would see their monthly rates increase by $3.

Westar serves nearly 700,000 customers in eastern and central Kansas, including the cities of Topeka, Wichita and Pittsburg. The Topeka-based utility has 7,200 megawatts of electricity generating capacity.