Solid Oxide Fuel Cells (SOFCs) have been proposed for Combined Heat and Power applications, but suffer from slow startup and limited cycling. In this work the heat exchanger of a residential furnace is modified and a SOFC stack is integrated in the combustion process. Specifically, the SOFC generates electricity by electrochemically oxidising remainingfuel in the combustion exhaust. The SOFC stack is thermal cycled as the residential furnace undergoes 200 on/off cycles. A rapid startup rate of 215° C/ min and a rapid cool down rate of 205° C/ min are achieved. The stack produces a high power density exceeding 150 mW/cm2.