In this study, the energy consumption of online (streaming or video on demand) lectures is compared with on-site lectures in the case of the Garching campus of the Technical University of Munich (TUM). The energy consumption is calculated using data collected by a survey, own measurements and literature research. On-site lectures at the TUM consume up to two orders of magnitude more energy than digital formats, making any combination of both always more energy intensive than purely online lectures. Transportation turns out to be the factor with the highest energy consumption. In scenarios with a decreased impact of transportation, e.g. regarding universities with dormitories on campus, hybrid or purely on-site lectures can become more favorable in terms of energy consumption, especially if several on-site lectures are attended in one day.