This paper presents the results of stationary off-design modelling of a micro-combined heat and power unit with solid oxide fuel cells. Mathematical models of the main components of the system with nominal power output of 1.6 kW were developed and implemented in the commercial modelling software Aspen HYSYS 8.0. The purpose of the study was to perform an analysis of possible operating conditions of the power system, using methodology which makes it possible to track changes in electrical and overall efficiency. Electrical load, fuel and oxidant utilization were varied to observe changes in performance of the micro-CHP unit. Performance maps were created to determine optimal working conditions to achieve either maximum electrical efficiency or power. The currently analysed system exhibits electrical and overall efficiencies exceeding 40% and 80%, respectively. Copyright (C) 2015, The Authors. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications, LLC.