[en] This research aims at analysing investment strategies of firms which are in an oligopolistic situation. After a brief description of the physical characteristics of an electric system, the author describes the reforms and defines the problematic of an investment in electricity production within markets in imperfect concurrence. In a first part, the author analyses the heterogeneity (either exogenous or endogenous) and technology choices of oligopolistic firms. In case of an exogenous heterogeneity, he studies the impact of the number of firms on investment decisions. In the second part, the author examines the regulations introduced in industries in imperfect concurrence: electricity production by a public firm and interaction between emission allowance market and investment