The number of smart devices connected h24 to the electric plant of an house is continuously growing with a clear impact on the energy consumption footprint. In the near future the stand-by consumption of these appliances will represent about the 15% of the total house consumption, a remarkable percentage intended to increase due to the growing number of smart devices contained in the house of tomorrow. In the presented scenario smart houses play an important role to reduce the stand-by consumption footprint introducing new strategies able to autonomously recognize these energy wastes. In 1999 the International Energy Agency launched the one-watt initiative with the aim of fighting this problem, today's smart homes can contribute to reduce the phenomenon with a 60% saving. Different strategies can be used in order to recognize a stand-by state, they can be divided in supervised and unsupervised approaches. In this paper we present an algorithm for each kind of approach comparing the performance of the two single approaches with the aim of proving that unsupervised techniques are ready to be widely adopted. An experimental evaluation concludes the paper.

Energy management, and in particular its efficient optimization, is one of the hot trends in the current days, both at the enterprise level (optimization of whole corporate/government buildings) and single-citizens' homes. Energy efficiency is generally function of out-door techniques -- renewable energy, smart energy production and distribution, etc. -- and in-door techniques; in particular, very few energy managers -- each of us can be an energy manager of his own home - can state "who, when and why is consuming", conversely this knowledge is fundamental in order to diminish wasting of energy. Recent studies show that the energy wasted in the overall consumption is about the 30% of the total amount; examples of potential energy wasting are printers and PCs on during the night, status LED of different devices (TV, set-top-box, etc.) and/or lights, lights during normal day-light time, etc.