Retail natural gas utility charges in Colorado would decline 9-10% beginning April 1 under a proposal by Xcel Energy Inc. combination utility Public Service Company of Colorado. Xcel said in a filing with the Colorado Public Utilities Commission (PUC) that the quarterly gas cost adjustment would result in a 9% decrease in residential bills and a 10% reduction for small businesses. Meanwhile, residential utility electric rates are expected to increase about 3.5%. For residential customers that use an average of 42 therms/month in the spring, the commodity prices dips to 2.41 cents/therm versus 3.48 cents/therm a year ago, a decline of about $3.00 a month. For small businesses that average about 185.2 therms monthly, the rate would drop to 2.38 cents/therm, a reduction of slightly more than $13. The revised rates require PUC approval.