Nowadays increasing energy efficiency is one of the main objectives of manufacturing systems so as to remain competitive despite of the foreseen increase in energy prices for the next years. We propose a novel queuing-based model for the appreciation of the energy consumption on a company base, so as to optimize the total energy costs due to electricity utilization.We propose an analytical model based on the extension of the M[x]/M/∞ model where arrivals of the queuing model represent the statistical distribution of switch-on of a generic set of machines and departures represent statistical distribution of the resources switch-off. This model can be easily used to assess and establish the contract with the energy supplier under optimal parameters of contractual power, based on its tariff components. Numerical examples are offered to show the applicability of the proposed model.