Design-point and part-load characteristics of a solid oxide fuel cell (SOFC) system, fuelled by methane and hydrogen, are investigated for its prospective use in the residential application. As a part of this activity, a detailed SOFC cell model is developed, evaluated and extended to a stack model. Models of all the required balance of plant components are also developed and are integrated to build a system model. Using this model, two system base cases for methane and hydrogen fuels are introduced. Cogeneration relevant performance figures are investigated for different system configurations and cell parameters i.e. fuel utilization, fuel flow rate, operation voltage and extent of internal fuel reforming. The results show high combined heat and power efficiencies for both cases, with higher thermal-to-electric ratio and lower electric efficiency for the hydrogen-fuelled cases. Performance improvements with radiation air pre-heaters and anode gas recycling are presented and the respective application limits discussed. (c) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.