The article analyzes some methods for calculating the loss of active power in lowvoltage industrial networks, taking into account the main influencing parameters. Equivalent resistance and losses of active power in radial and trunk circuits are determined. The errors of the equivalent resistance and the loss of the active power of the circuits relative to the reference values are calculated. Graphic dependencies of the equivalent resistance of the radial and trunk circuits of the industrial networks are taken into account, taking into account switching devices on the lines in the functions of such parameters as the total cross-section of lines, average lengths, cross-sections of lines and ambient temperature, and with a change in the line load factor. The proposed nomograms are highly accurate and can be used in practical calculations.