A simultaneous optimization of the design and operation of a district heating, cooling and power generation plant supplying a small stock of residential buildings has been undertaken with regards to cost and CO?2 emissions. The simulation of the plant considers a superstructure including a SOFC-GT combined cycle, a compression heat pump, a compression chiller and/or an absorption chiller, and an additional gas boiler. The Pareto-frontier obtained as the global solution of the optimization problem delivers the minimal CO?2 emissions rate achievable with the technology considered for a given accepted investment, or respectively the minimal cost associated with a given emission abatement commitment.