This paper presents mapping method to show characteristics of cogeneration systems (CGS) for the reduction of carbon dioxide emission and economy. In this method, effects of CGS can be consolidated into rated reduction ratio, relative reduction ratio map, demand repetition map and weight map. By lapping these maps, it can be easy to evaluate compatibility with each building types and optimal installed capacity. Analyzed charts are useful to evaluate quantitative effects of CGS for various areas and price rates of electric/gas from average annual demand of electricity and heat.