In the recent year’s low power computing systems have gained popularity. Networks, which use low power computer systems and transmitted data by using wireless connection are called wireless sensor networks. Nowadays, the most topical researches pertaining to wireless sensor networks are grounded on the new optimization of structure of network transmission protocol, the routing optimization in transmission network, optimization of network structure, as a result of which the life circle of wireless network sensors is possible to increase. This paper provides a structural view on the life expectancy of a wireless sensor network with an autonomous power supply without the option of renewing energy. The factors, that affect total life expectancy of a wireless sensor network are defined as well.