Retail natural gas utility bills in Colorado are headed up, according to Xcel Energy's Denver-based combination utility, which sees a 12-16% rise in monthly bills coming in 2Q2017 compared to the same quarter last year. Xcel made a quarterly gas cost adjustment filing to state regulators on Wednesday calling for residential gas rates to increase to 33.6 cents/therm next quarter, compared to 24.1 cents/therm for the second quarter last year, a 12% increase to average bills of a little more than $30 monthly. For small businesses, the rate increases to 33.3 cents/therm from 23.8 cents/th in 2Q2016, an increase of 16% to average bills of $125 each month. Xcel asked the Colorado Public Utilities Commission to approve the rates to be effective April 1.