Technology dynamics is endogenized into a bottom-up energy systems model. Mixed integer programming is used to incorporate into the model the non-convex relation between declining specific investment in energy technologies and overall experience or capacities installed. The initial results achieved with this approach show the importance of early investment in new technology developments. New technologies will not become cheaper irrespective of research, development, and demonstration (RD&D) decisions; they will do so only if determined RD&D policies and investment strategies enhance their development.