Energy demand management for residential users is a promising research area within the Smart Grid revolution. The whole energy generation and distribution system performance can indeed be improved by optimizing the house energy management while still meeting the energy needs of customers. In this paper we propose Non-Cooperative models for the optimal planning of energy loads of a single house, with the final goal of minimizing the energy bill. A Pre-emptive variant of the model is also presented where some appliances activities can be interrupted in some phases. Finally, Cooperative models are defined for jointly managing the energy consumption of a group of users in order to easily decrease the aggregated maximum power demand, thus reducing the peak absorption. Numerical results, obtained applying models on realistic data, are presented and discussed.