Over the past quarter century, building energy efficiency has focused on improvements to components and equipment. While component efficiencies increased dramatically, the size of our homes and the number of energy using stuff has increased even faster. Looking forward, the focus for energy efficiency in buildings will need to shift to systems rather than components. This shift will involve transformations in how we build, and where and how we live. This shift does not mean that we can ignore component efficiency, because energy using appliances are proliferating, but that we need to take a more holistic approach to our communities.