Experimental results of the performance of a solid oxide fuel cell (SOFC) unit are presented. The unit was designed, manufactured and tested at the VTT Technical Research Centre of Finland. The 10 kW power class SOFC stack and stack module were designed and manufactured by Versa Power Systems (VPS). A successful commissioning test of the unit was conducted in 2010. Long term testing of the unit was started in November 2010. The unit has been operated with natural gas for over 1500 hours supplying electricity to the local grid. The unit has shown robust and uninterrupted performance. Stack DC efficiency of 60% and system net AC efficiency of 43% has been measured during the operation.