A new configuration for an existing PEM fuel cell based residential micro-cogeneration system has been proposed in which the conventional low temperature PEM fuel cell is replaced with a high temperature one. Detailed mathematical models for the fuel processor, HT- PEM fuel cell stack and all other components of the plant have been developed. The electrical and thermal performance of the system have been determined and the corresponding results have been compared with the performance indices achieved for the previous plant. The electrical efficiency and the primary energy savings index obtained for the proposed system are 29.21% and 17.50% respectively which are considerably higher than the ones obtained for the existing LT-PEM based plant (21.18% and 6.07%). In order to enlighten our understanding of the behaviour of the system a parametric study on the key parameters of the system has been carried out.