Information technology can increase energy efficiency by improving the control of energy-using devices and systems. Awareness of this potential is not new—ideas for applications of information technology for energy efficiency have been promoted for more than 20 years. But much of the potential gain from the application of information technology has not yet been realized. Today a combination of new requirements for the operation of the electricity system and the development of new technology has the potential to cause a rapid increase in the pace of adoption of improved controls. In this paper we discuss one promising avenue for technology advancement. First, we review some basic concepts with emphasis on open software-architecture. Then we describe the components of XBOS, a realization of this open software-architecture. XBOS has the ability to monitor and control many different sensors and devices using both wired and wireless communication and a variety of communication protocols. Finally, we illustrate the capabilities of XBOS with examples from an XBOS installation in a small commercial office building in Berkeley California.