The paper describes a method for calculating the unutilized regenerative braking energy in urban electric transport networks. The method has been developed applying principles of the probability theory and uses on the electric transport schedules. Being bases on the experimentally obtained power diagrams the method allows estimating the economical aspects of the of regenerative braking energy utilization not only for a current situation but also for the future in view of the plans concerning renovation of the electric transport fleet and changes in the transport organization.