In the day-to-day operation of a power system, the system operator repeatedly solves short-termgeneration planning problems. When formulating these problems theoperators have to weigh the riskof costly failures against increased production costs. The resulting problems are often high-dimensionaland various approximations have been suggested in the literature.In this article we formulate the short-term planning problem as an optimal switching problem withdelayed reaction. Furthermore, we proposed a control variable technique that can be used in MonteCarlo regression to obtain a computationally efficient numerical algorithm.