Abstract <p>The problem of determining the energy intensity of a thermal energy storage unit (TES) installed at a metro traction substation for receiving excess recuperation energy during braking of electric rolling stock (ERS) is considered. The distribution of the ERS recuperation current is described for the thrust of other ERS and the auxiliary needs of the ERS, as well as for ERS braking rheostats. The main technical solutions for receiving excess recuperation energy in the form of various kinds of energy storage devices are listed, arguments in favor of TESs are given due to their simplicity, high power and energy intensity, and relatively low price. The principle of operation of TESs and possible types of refrigerant for the storage element in a storage tank, including ones with a heat-capacitive phase transition, are described. The dependences of the current of a traction substation, as well as the current, voltage, and received energy of the capacitive energy storage as a function of time, are obtained. Mathematical expressions are proposed to determine the components of the TES energies depending on the time of day and the current TES energy reserve in real time, taking into account the initial (minimum) level of energy reserve, as well as taking into account the reception of excess recuperation energy and the parallel process of energy transfer to the heating main. It is determined that, under the operating conditions of the TES, taking into account the average heating power of the premises equal to 75 kW, the total energy consumption of the TES should be about 4000 MJ.</p>