Demand for data services is expected to increase due to emerging technologies such as streaming, cloud gaming, blockchain, artificial intelligence, machine learning and virtual reality. Mobile data traffic is projected to quadruple by 2028, with 5G networks taking up a large share of the traffic. Demand for data centre services is also expected to rise due to blockchain and machine learning applications. Energy use does not increase proportionally with traffic volumes, and the average energy consumption of video streaming is fairly low. Decommissioning of legacy networks such as 2G and 3G offers a major opportunity to reduce mobile network energy use.