Commonwealth Edison and other power suppliers are challenging the state's plan to help finance the FutureGen clean-coal project by charging Illinois electricity customers.
Edison and the Illinois Competitive Energy Association plan to go to the Illinois Appellate Court.
They will challenge the surcharge the Illinois Commerce Commission approved in December.
CEA President Kevin Wright says the commission lacks the authority to make electricity customers help finance the federally backed project.
Commerce Commission spokeswoman Beth Bosch says the agency knows about the planned appeals but hasn't seen arguments yet.
FutureGen has been the subject of political and financial difficulties for years.
It was initially proposed as a new power plant.
But now the project will retrofit a western Illinois coal-fired plant.
Carbon dioxide would be removed from fuel and stored underground.