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 from diverse 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 from the interactions. The workshop seeks submissions of early-stage research and novel ideas that will generate interesting discussion, e.g., unconventional, promising ideas with early results. Submissions about firsthand experience, lessons, challenges and problems from building and operating real-world systems are also welcome.