To date, optimization models of uncertain endogenous technological change models commonly add cost resulting from overestimating technological learning rates into an objective function with a subjective risk factor. This paper argues that applying risk-constrained cost minimization to uncertain endogenous technological change models could be more practicable for decision-making support since it is more explicit and tangible to set an acceptable extra cost than to set a pure subjective risk factor value. This paper applies the risk-constrained method to analyze a simplified energy system with three technologies.