The U.S. Department of Energy (DOE) Building Technologies program has set aggressive goals for energy efficiency improvements in buildings that will require collaboration between the DOE laboratories and the building industry. This report details the development of standard or reference energy models for the most common commercial buildings to serve as starting points for energy efficiency research. These models represent reasonably realistic building characteristics and construction practices. Fifteen commercial building types and one multifamily residential building were determined by consensus between DOE,

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Commercial buildings have a significant impact on energy use and the environment. They account for approximately 18% (17.9 quads) of the total primary energy consumption in the United States (DOE 2005). The energy used by the building sector continues to increase, primarily because new buildings are added to the national building stock faster than old buildings are retired. Energy consumption by commercial buildings will continue to increase until buildings can be designed to produce more energy than they consume. As a result, the U.S. Department of Energy's (DOE) Building Technologies Program has established a goal to create the technology and knowledgebase for marketable zero-energy commercial buildings (ZEBs) by 2025. To help DOE reach its ZEB goal, the Buildings and Thermal Systems Center at the National Renewable Energy Laboratory (NREL) studied six buildings in detail over the past four years to understand the issues related to the design, construction, operation, and evaluation of the current generation of lowenergy commercial buildings. These buildings and the lessons learned from them help inform a set of best practices-beneficial design elements, technologies, and techniques that should be encouraged in future buildings, as well as pitfalls to be avoided. The lessons learned from these six buildings are also used to guide future research on commercial buildings to meet DOE's goal for facilitating marketable ZEBs by 2025. The six buildings are:

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Reported as: annual value Cogeneration Electrical Energy Output Electrical energy produced by cogeneration equipment that is either (a) used at the facility in a way that offsets the consumption of purchased energy or other energy generated at the facility, or (b) exported from the facility and used elsewhere (e.g., electrical energy fed to the utility grid). Units: kWh, Btu, or Joules Reported as: Monthly totals (tabular), monthly daily averages (graphical), annual total, graph of peak day in each billing period. Cogeneration Fuel Use Fuel consumed by cogeneration equipment. Units: kWh, Btu, or Joules Reported as: Monthly totals (tabular), monthly daily averages (graphical), annual total, graph of peak day in each billing period. Cogeneration Losses = Cogeneration Fuel Use-Cogeneration Electrical Energy Output-Cogeneration Thermal Energy Output Units: kWh, Btu, or Joules Reported as: Monthly totals (tabular), monthly daily averages (graphical), annual total, graph of peak day in each billing period. Cogeneration Thermal Energy Output Thermal energy produced by cogeneration equipment that is either (a) used at the facility in a way that offsets the consumption of purchased energy or other energy generated at the facility, or (b) exported from the facility and used elsewhere (e.g., heat used at another facility). Units: kWh, Btu, or Joules Reported as: Monthly totals (tabular), monthly daily averages (graphical), annual total, graph of peak day in each billing period.