This paper presents the application of Demand Response (RD) to evaluate the flexibility of a customer group based on an aggregated stochastic demand model, whose behavior and decision making is based on recent statistical surveys. The sample of users is evaluated in two scenarios. First scenario applies a negative incentive on which 36% of the customers respond and overcome it. The second scenario uses a power peak tariff where customers voluntarily reduce the cost in their bill. About 5% of reduced peak demand is achieved with low effect on customer comfort.