A geothermic heater system for heating a geological formation includes a fuel cell stack assembly disposed at the surface of the geological formation and includes a plurality of fuel cells which convert chemical energy from a fuel into electricity through a chemical reaction with an oxidizing agent, thereby producing an anode exhaust and a cathode exhaust. The geothermic fuel cell system also includes a combustor disposed within a bore hole of the geological formation. The combustor combusts a mixture at least one of the anode exhaust and the cathode exhaust to produce a heated combustor exhaust. The combustor discharges the heated combustor exhaust to heat the geological formation.