In the past decade, video communication systems have conquered the world. Nowadays, billions of people worldwide use a wide variety of online video services every day. Applications range from videoconferencing and video streaming to social networks and surveillance scenarios. Concurrently, recent studies have found that in 2018, roughly 1% of the global greenhouse gas emissions could be attributed to these online video services, highlighting the need for research targeting energy efficient online video systems. In this talk, we give a broad overview on the energy consumption of these systems and discuss latest research and trendsetting ideas to reduce their carbon footprint.