It is obvious that a contract on the consumption of electricity must be kept in order to well operate companies from the view point of cost-effectiveness and eco-friendliness. In general, if the amount of the electricity consumption is over the contract demand, the company must owe the excessive penalty cost. In such a background, we are curious about the optimum switching strategy of air-conditioners which may occupy the large amount of the operation cost. In this thesis, we use a Markov decision process model to analyze the optimum switching policies. In addition, we also take into account the possibility of failure occurrences of air-conditioners and other factors in the modeling
