Combined heat and power (CHP) systems in residential settings are uncommon in the United States, but they provide many benefits in terms of energy and cost savings. When comparing a conventional furnace system to one with CHP in a residence located in Boston, MA, significant cost and energy savings are possible. In this study, a direct comparison is made between a gas-fired furnace system with cooling and a CHP system of various parameters for a 4,160 ft2 house. The system sizes investigated in this study are 1, 2, 5, and 10 kW, with an electric efficiency of 15 to 50%, an overall efficiency of 80 to 90%, and start-up times of 0.1, 0.5, 1, and 2 hours. The load following mode is also varied between thermal and electric. The program used to generate these results is eQuest, and two different models, both with code-compliant constructions, air-side systems, water-side systems, and internal loads, have been directly compared. The conventional system costs $4,976 per year for both electricity and natural gas, while the CHP system can reach prices (depending on the parameters) of less than half the conventional. The results of this study advocate for the more widespread use of CHP systems in general and in residential buildings, due to their ability to save energy and money.