Minnesota utility regulators have approved a natural gas rate increase for the Minnesota Energy Resources Corp., but they don't have a final number yet.

The third-largest natural gas utility in the state, with more than 200,000 customers in Twin Cities suburbs, Duluth and Rochester, had asked the Minnesota Public Utilities Commission to allow it to make a 5.5 percent rate hike for a total increase of $14.2 million.

The commission last November approved an interim increase of 4.2 percent or $10.8 million, which went into effect in January and cost the typical customer $3.35 per month.

An administrative law judge ruled in August that the rate increase should be only 1.8 percent, but the final decision, which is yet to be calculated, will be somewhere close to the interim rate increase approved by the commission almost a year ago.

If the final number comes in lower than the interim rate, customers will get refunds with interest.

A major factor in determining the rate increase is the company's increased spending on conservation programs, according to the commission. About $3.6 million of the final increase, over 40 percent, is due to increases in those programs.

This is the company's third rate hike request since 2008, when rates went up 5.5 percent. In 2010, rates rose 4.1 percent. The increases only apply to the cost of delivering gas. Utilities don't make money on gas itself and fuel price changes are passed on to customers.

Customers' overall payments are lower today than six years ago, when natural gas prices peaked, according to the company.

Minnesota Energy Resources, a subsidiary of Chicago-based Integrys Energy Group, serves 165 communities, including Cottage Grove, Eagan, Farmington, Lakeville, Prior Lake and Rosemount.

Adam Belz • 612-673-4405 Twitter: @adambelz