This paper proposes a model for the optimal choice among three alternative new markets for Québec electricity: new electrical processes in the industrial sector, electricity intensive industries, exportating electricity to other provinces and states. A partial equilibrium is computed between a supply model and demand models, via mathematical programming. This work includes features that are unusual in energy modelling, especially the inclusion of financial constraints in the linear programming model of electricity supply, and the estimation of demand functions via a detailed techno-economic demand model.