As the cost of operating coal-fired power plants continues to rise, customers who buy power from coal-reliant electric companies, including Rocky Mountain Power, could see their power bills go up, according to a new report from the Sierra Club. The report released Wednesday claims that increased regulation of coal emissions, aging infrastructure and the rising price of coal â as well as more federal subsidies for alternative-energy sources â mean it may be more cost effective for energy companie... <img src="http://mngislctrib.112.2O7.net/b/ss/mngislctrib/1/H.17--NS/0?&pageName=RSS" height="1" width="1" border="0" alt=""/> <iframe src="http://www.sltrib.com/csp/mediapool/sites/sltrib/pages/garss.csp" height="1" width="1" > </frame>