The rising energy consumption of the ICT industry has triggered a quest for more sustainable, i.e. energy efficient, ICT solutions. Software plays an essential role in finding these solutions, as software is identified as the true consumer of power. However, in this context, software is often treated as a single, complex entity instead of the interrelated elements that it actually consists of. Although useful results can be gained, this approach fails to provide detailed insight in the elements that invoke specific energy consumption behavior. As a result, software vendors are not able to address energy consumption on software level. In this paper, we propose an energy consumption perspective on software architecture as a means to provide this insight and enable analysis on the architectural elements that are the actual drivers behind the energy consumption. In support of this perspective, we also position sustainability as a potential quality attribute thereby provide a means to quantify energy consumption aspects related to software. In a case study using a commercial software product the perspective and quality attribute are applied, demonstrating the potential by achieving an energy consumption saving of 67.1 %.