This paper presents a model of a combined heat and power system, also known as cogeneration, for the generation of electricity and steam for in situ bitumen extraction operations. The model simulates the operation of a gas turbine-electric generation system with the hot exhaust gases from the turbine being directed to a boiler for steam production. Alternately, a topping steam turbine-electric generation system with exhaust steam directed to the in situ operations is simulated. The model provides estimates of the fuel requirements and electricity generated by the combined process. It enables the investigation of the relationships between electricity generation, steam production and fuel requirements for these operations. Included is an illustrative example of the application of the model for the assessment of the economics of the steam assisted gravity drainage (SAGD) process using alternate fuels, natural gas and petroleum coke.