The global commitment towards a sustainable future energy supply portfolio yields several new technical, economical and political challenges. Thus, understanding the drivers of energy technology investment costs is of key importance. Consequently, the core objective of this book is to identify the simultaneous impact of, on the one hand, energy and raw material prices and technological learning effects, on the other hand, on the investment costs of electricity technologies. Results depict a significant impact of steel prices on wind onshore investment costs, whereas offshore wind investment costs are additionally affected by concrete prices. Steel and concrete prices show an even stronger impact on biomass CHP investment costs. In contrast, the silicon price holds a marginal impact on Photovoltaic investment costs. Similar results are derived for small-scale hydro power investment costs, where energy and raw material prices do not explain their development. In general, technological learning by doing effects are largely compensated by the impact of raw material prices in the case of wind and biomass CHP technologies whereas the opposite effect is identified for Photovoltaics.