In this case study four actual energy efficiency projects are analyzed with two traditional engineering economy capital budgeting methods - internal rate of return and payback period - and the results compared with those obtained using the capital asset pricing model (CAPM). The alternative scenarios of the future states-of-the-world necessary for the latter are based on information available in Department of Energy reports. The traditional and CAPM approaches result in different economic conclusions for some of the projects. These differences are analyzed and the implications for certain types of improvement projects and equipment replacement problems as well as financial decision-making in general are discussed.