This is not an insignificant issue given the potential large increase in rates.

OG&E's $1.1 billion environmental compliance plan in Oklahoma draws critics | NewsOK.com

A $1.1 billion plan for environmental compliance by Oklahoma Gas and Electric Co. will go before regulators in March, but several parties are questioning the timing and details of the utility’s proposal.

OG&E wants to install scrubbers at two of its Sooner coal units and convert two Muskogee coal units to natural gas. It also wants to replace its aging Mustang plant in western Oklahoma City. The utility must comply with federal regulations for regional haze and mercury and air toxins.

If approved by the Oklahoma Corporation Commission, the plan would increase residential customer bills by 15 percent from 2015 to 2019. The costs would be phased in each year and added to customer bills in the form of a separate line item called a rider.