Primary energy factor (PEF) is energy indicator used for quantifying the primary energy use of a plant. It is calculated by using the methodology described in the European Standard EN 15316-4-5. Using this calculator, the coefficient of Primary Energy Factor (PEF) is obtained by consumed heat, fuel input to the Heating Plant (HP) and Combined Heat and Power (CHP), electricity production of the cogeneration plants, fuel and its primary resource factor. This factor indicates how much primary energy is used to generate a unit of heat and electricity. This factor shows heat and electricity production efficiencies and allow to make comparison among different DH companies or different scenario. The lower is primary energy factor the higher is energy production efficiency of DH company. The main users of tool can be DH operators to have an overview about the energy efficiency of heat distribution processes or heat losses in the grid. The tool can be also used by municipalities and national stakeholders to evaluate the DH companies and write specific regulation acts.