As the avoidance of CO2 emissions in energy production is gaining more and more attention in our time, the focus is on renewable energies is more significant. However, in the past, these enegy supply technologies have proven not to be cost favorable. It is necessary to investigate how and by what the investment costs of the respective energy sources have changed over time. Therefore, the investment costs of renewable and other technologies were analyzed and compared. For this purpose, the learning curve was used, which allows a qualitative description of the investment costs over time. It has been found that photovoltaic has a high learning rate compared to the other technologies used for energy production. The learning rate for wind energy approaches zero. There are also technologies such as nuclear energy, for example, which even have "negative" learning. To get more meaningful analysis, more data is needed. On the basis of the learning curves at least it can be seen that the investment in renewable energy sources is worthwhile.