The proposed in the paper heat source cogeneration potential assessment method, is based on the heat sources group gathered heat load duration curve analysis and optimization of installed thermal power of cogeneration unit. Heat loads of sources group are converted into the normative climatic conditions. For the method verification are used Lielvarde heat source operating data in year 2007. The results show that quantitative indicator value differences are small and methods of use are correct. There is investigated cogeneration optimal heat capacity correlation with the source of the average heat capacity, which significantly facilitates the assessment of the potential of CHP in the event if there are available only year fuel consumptions. During the methods inspection process is performed Lielvarde heat source cogeneration thermal capacity optimization and found that the installed capacity is less than optimal. There are observed possible amounts for heat and power generation in optimal capacity case.