Application scenarios of WSN implementations are really broad. Due to their typical characteristics, such advantageous power consumption, wide communication coverage and relatively broad sensing possibilities, many application fields can be covered. In this paper, the problematic of power metering is targeted. Places with shared power sources, where electricity usage is calculated equally according to the number of users, are often misused by single users for illegitimate power usage. Special WSN was developed and implemented in a scenario of multi-store parking garage to solve this problem.