Abstract: In this paper a new method of using a wattmeter electrodynamometer to verify the Tellegen's theorem is presented. It is proved that this me-thod can be applied not only to networks excited by dc or sinusoidal ac sources, but also to networks excited by the same periodic non-sinusoi-dal sources. Detailed experimental information of the general case of excitation, by same periodic non-sinusoidal sources is also provided. The experime-ntal results fully verify the validity of this new method.