The much-needed energy transition brings special focus on fuel cell micro-combined Heat and Power (mCHP or micro-CHP) systems for residential uses, one of which is a Solid Oxide Fuel Cell (SOFC), fed by natural gas, designed to provide continuously 1.5 kWel with an associated amazingly high expected Low heating Value (LHV) electrical efficiency of 60%. This power output can be modulated as desired down to 500 Wel and heat can also be recovered to partially contribute to the heat demand of the household. This system has been installed in a laboratory environment and has been specifically instrumented in order to evaluate its performance with different thermal loads and electrical output power settings. In this paper, focus is brought on the resulting thermal output and efficiencies, both thermal and electrical, which have also been modelled with great goodness of fit. With several electrical power outputs between the 500-1500 Wel range, this study shows total High Heating Value (HHV) total efficiencies up to 88-89% at minimal return temperatures (around 20°C) in the heat recovery circuit. Maximum LHV electrical efficiency has been found to be equal to 57% at nominal output power (regardless of the thermal loads), which is close to the manufacturer’s target of 60%.