Abstract The drive for achieving high values of fuel utilization factor, in the last years, has led to an increasing attention to combined heat and power (CHP) plants. In this scenario, the district heating allows to achieve high conversion efficiencies by centralizing in few large power plants the need of thermal energy in household sector. The power plants that feed the District Heating Networks (DHN) usually work by combined heat and power set-up. District Heating Networks have found a large development in the last decades. The main advantage of DHNs is the reduction of pollutant and thermal emissions in the city area. Further, the large use of DHNs increases the safety, due to the absence of combustion systems at the final users of thermal energy. For the same reason also the transportation of fuel in the city area can be drastically reduced by the use of DHNs. On the basis of the previous observations, in this study a new software for the DHNs design and analysis is described and validated. This software, which has been developed by University of Bologna, is based on the Todini-Pilati algorithm generalized by the use of Darcy-Weisbach equation. More in details, in this paper the main physical-mathematical models adopted in the realized software, called Ca.R.Di.F., and its validation are described.