This paper provides a methodology to evaluate end use options to reduce primary energy consumption and CO₂ emissions associated with buildings. First, the paper discusses alternative energy efficiency metrics, their uses, and limitations. In particular, limitations of site energy and cost as meaningful societal metrics are reviewed, along with the challenges associated with alternative metrics such as full fuel cycle energy efficiency and CO₂ emissions. In addition, the paper provides a methodology and example calculations for evaluating the site energy, full fuel cycle energy, and CO₂ emissions of targeted direct use options. Results of the sample calculations show that natural gas water heaters can reduce primary energy consumption and CO₂ emissions significantly compared to equivalent electric resistance water heaters. Variations in calculated reductions occur depending on the fuels used to generate electricity and region selected for analysis.

Units: Dual