Residential combined heat and power (CHP) systems using fuel cell technology can provide both electricity and heat and can substantially reduce the energy and environmental impact associated with residential applications. The energy, environmental, and economic characteristics of fuel cell CHP systems are investigated for single-family residential applications. Hourly energy use profiles for electricity and thermal energy are determined for typical residential applications. A mathematical model of a residential fuel cell based CHP system is developed. The CHP system incorporates a fuel cell system to supply electricity and thermal energy, a vapor compression heat pump to provide cooling in the summer and heating in the winter and a thermal storage tank to help match the available thermal energy to the thermal energy needs. The performance of the system is evaluated for different climates. Results from the study include an evaluation of the major design parameters of the system, load duration curves, an evaluation of the effect of climate on energy use characteristics, an assessment of the reduction in emissions, and a comparison of the life cycle cost of the fuel cell based CHP system to the life cycle costs of conventional residential energy systems. The results suggest that the fuel cell CHP system provides substantial energy and environmental benefits but that the cost of the fuel cell sub-system must be reduced to roughly $5001kWe before the system can be economically justified.