Capital intensity and investment longevity are just two among the many peculiarities of the electricity industry. Also for the sector of energy transmission these properties play an important role from an economic point of view. Assets are often used for a long time beyond the normal useful life, but after the end of this period, they are only shown with the so-called "reminders" in the company's balance sheets. In fact, these plants continue to be of great value for their continued operation. The aim of this master thesis is therefore to determine the capital stock of the European transmission system operators. This was realized with the aid of an EXCEL model. With this model it was possible to simulate the historical development of the capital stock of the European transmission system operators. The results of the model show a clear difference between the gross and net capital stock. This is due to depreciation, which reduces the real value of the assets. The detailed research results are discussed in the conclusion of the work.