Retail natural gas rates in Colorado are headed up by 13-14% in the first quarter, according to Xcel Energy Inc.’s Denver-based combination utility, Public Service Company of Colorado.

The increase will be somewhat moderated by an offsetting decrease in utility electricity charges during the first quarter, an Xcel spokesperson said.

Based on Xcel’s filings on Thursday to the Colorado Public Utilities Commission (PUC), the quarterly gas cost adjustment (GCA) will send retail bills upward compared to the first quarter of this year.

“Natural gas bills still are lower than a couple of years ago, based on continuing historically low natural gas prices,” the spokesperson said. “Customer bills next quarter will be about 11% less when compared to customer bills for the first quarter of 2015.” He noted that natural gas bills are compared on an annual basis to better reflect seasonal use.

For a typical residential gas customer who paid 30.8 cents/therm in the first quarter this year or a monthly bill averaging $62.69, the rate will go up to 39.06 cents/therm, or about $70.82/month. Small business customers will pay 38.77 cents/therm, or $310.10/month in the first quarter upcoming, compared to a rate and bill in the first quarter this year of 30.48 cents/therm and $271.09/month.

In contrast, the quarterly electric commodity adjustment (ECA) indicates that Xcel power customers will experience a 2-3% rate decrease for the first quarter next year, compared to this year’s first quarter.

“With minor exceptions, costs associated with increases or decreases through the ECA and GCA are passed along to customers on a dollar-per-dollar basis,” the utility spokesperson said. “If approved by the PUC, the new rates would go into effect on Jan. 1 next year and remain in effect for three months.”