District heating and cooling system (DHC), which is responsible for supplying heat, cold, and electricity to the region, often have the ability to generate electricity as well as generate heat and cold. In our previous study, we proposed an operational method that would enable DHC to simultaneously supply electricity to the electricity market in Japan while fulfilling its responsibility for local demand, as well as a method for evaluating its economic efficiency. This study focuses on the issue that environmental value is not yet fully evaluated in many electricity markets around the world and proposes a method for determining an operation that maximizes the total of the economic value and environmental value of DHC. In addition, authors examine the possibility of changes in the optimal DHC equipment configuration, operation methods, and conditions through sensitivity analysis of carbon prices and CO2 emission factors. Based on these research results, conditions under which it will be necessary to update the DHC equipment configuration and operation methods are organized in future fluctuation scenarios of carbon price and CO2 emission factors.