We propose an end-to-end approach to describe the energy usage of video delivery within a content delivery framework, and use this to investigate the energy usage behavior of two popular coding schemes, namely, H.264/AVC and H.265/HEVC. Our study based on the proposed model is backed up by measurements of encoding and decoding energy usage of a sample video and shows that, from an end-to-end perspective, taking into account all the elements of a content delivery network, neither of the coding formats is always dominant in terms of energy saving. We also find that the popularity of video content is a key parameter for predicting which encoding scheme saves most energy. In particular, we find that H.265 encoded content results in lower energy...