In this paper, an optimal deployment with respect to capacity sizes and types of DG (distributed generation) for CHP (combined heat and power) systems within microgrids was presented. The objective was to simultaneously minimize the total net present cost and carbon dioxide emission. A multi-objective GA (genetic algorithm) was applied to solve the planning problem including the optimization of DG type and capacity. The constraints include power and heat demands constraints, and DGs capacity limits. The candidate technologies involved in this study include CHP generators (with different characteristics), boilers, thermal storage, renewable generators (wind and photovoltaic), and a main power grid connection. The surplus/deficient electricity can possibly be sold to/bought from the main grid. Costs of CHP generators are based on their types and the capacity range. The approach was applied to a typical CHP system within microgrid system as a case study, and the effectiveness of the proposed method was verified.