The Micro energy grids (MEGs) are expected to play a vital role in designing smart grids because it reduces energy expense and gas emissions by utilizing renewable and non-renewable distributed energy resources. However, currently, problems exist concerning the design and utilization of MEGs. In our previous work , we assume that the distributed generators put the priority on electricity production and the surplus/deficient electricity can be sold to/bought from the utility grid. The surplus/deficient heat can be stored/or supplied by thermal storage tank, boiler and/or electrical heater. In this study the distributed generators put the priority on heat production and the deficient heat can be supplied by the boiler and/or electrical heater. Multi-objective particle swarm optimization (MOPSO) algorithm is used to specify the optimal combination of components and optimal sizing of all MEG components for minimization of the total system cost and total carbon dioxide emissions simultaneously.