The Forum for Energy Models and Energy Economic Systems (FEES) represented an open platform for the close-up experience-based exchange between developers and users of energy models from the fields of research, policy, and industry. One of the major tasks of the Forum was to perform model experiments with various models and model approaches while using a harmonized set of data from joint case studies.The goal of the Model Experiment V was the improved understanding of the effects of the innovation process on energy- and macroeconomic development. This meant determining the relationships between technological progress and costs as well as market intensities/diffusion on the background of various framework conditions. Thereby diverging methodical approaches, various degrees of resolution, different theoretical groundwork or exogenous model data (e.g. technology parameters, costs/costs development of energy technology) were taken into particular consideration as regards their relevance towards the different analytical outcomes.