Power has become a central issue in the design of modern computer systems. It affects a huge variety of systems, including mobile devices, embedded networks, and large scale data centers. While there has been significant research into energy efficiency and tradeoffs to performance and other metrics, there is still significant untapped opportunity to optimize across the systems architecture stack, comprehending the entire spectrum from silicon design to storage devices to mobile endpoints and datacenter designs. With several technology disruptions on the horizon, there is the impetus to rethink how traditional boundaries between hardware and software need to evolve, and how associated designs and implementations need to change. HotPower provides a forum in which to present the latest research and to debate directions, challenges, and novel ideas about building energy-efficient computing systems. In addition, researchers coming to these issues from fields such as computer architecture, systems and networking, measurement and modeling, language and compiler design, mobile computing, and embedded systems will have the opportunity to interact with one another, explore cross-cutting ideas, and develop new perspectives on the problem domain.