The paper considers the accuracy of the approximate calculation of the potential funnel of square and rectangular mesh earth electrodes in homogeneous soil. For the approximate calculation of the potential at greater distances from the centre of the earth electrode, the expression for the potential field of a circular disk located on the surface of the earth is used, provided that the areas of the mesh earth electrode and the disk are equal or the resistance of the distribution is equal. The approximate results are compared with those obtained by the calculation using the mean potential method.