We consider an equilibrium problem with equilibrium constraints (EPEC) arising from themodeling of competition in an electricity spot market (under ISO regulation). For acharacterization of equilibrium solutions, so-called M-stationarity conditions arederived. This first requires a structural analysis of the problem, e.g.,verifying constraint qualifications. Second, the calmness property of a certainmultifunction has to be verified in order to justify using M-stationarity conditions.Third, for stating the stationarity conditions, the coderivative of a normal cone mappinghas to be calculated. Finally, the obtained necessary conditions are made fully explicitin terms of the problem data for one typical constellation. A simple two-settlementexample serves as an illustration.
