Energy efficiency is now a fundamental part of doing business in real estate and property management. If companies miss out, they risk falling behind in terms of market competitiveness. This City Energy Project resource provides a multidimensional, in-depth look at the business case for energy efficiency in buildings. It provides an overview of the basic financial arithmetic of energy savings, avoided operating costs, net income, and value, as well as a summary of case study data on what this arithmetic has meant to real projects and companies. The core of this report is the firsthand commentary of executives at three real estate companies—Jamestown LP, Physicians Realty Trust, and Praxia Partners—each at the leading edge of efficiency and sustainability in its respective subsector, and each with its own approach to the business case.