An energy-efficient and low-emissions solid oxide fuel cell (SOFC) combined heat and power (CHP) system is a promising electric and thermal energy generation technology for implementation in future commercial buildings. Recently developed performance models for kW- and MW-sized SOFC CHP systems have been integrated into a building energy simulation model of a medium-sized (7000 m(2)) office building to evaluate the potential of the system to lower annual utility costs and to reduce CO2 emissions. An optimized 175 kW SOFC CHP system successfully lowered annual utility costs by up to 14.5% over a baseline HVAC system in locations with space heating-dominant loads. Potential CO2 emissions were reduced by up to 62% over the baseline case for the optimized SOFC CHP systems. If the capital and installation costs of SOFC CHP systems are reduced in the near future, through the realization of cheaper, high-performance intermediate temperature SOFCs, the SOFC CHP system may be a promising energy-efficient and low-emitting alternative power and thermal energy cogeneration technology. (c) 2013 Published by Elsevier B.V.