Metrics for Energy Efficient Buildings: How Do We Measure Efficiency?

Secondary Author(s)

Goldstein, David

Report Number





Energy Efficiency; Buildings


Several mutually incommensurate metrics have been used to rate building energy efficiency. Metrics are constructed with two different goals: a broad goal of comparing different buildings with respect to their efficiency and the narrow goals of comparing all-electric buildings with those using two or more fuels. This paper discusses the comparative usefulness of broad measures of energy efficiency such as energy use per unit of conditioned floor space (Energy Use Index or EUI), the HERS Index and its commercial analogue the zEPI Index, and percent better-than-a reference-code. This comparison is performed in a policy context of how efficiencyin buildings is defined. It then looks at four possible ways of comparing fuels: normalized modified loads (used in the HERS Index and in the International Energy Conservation Code), site energy, source energy, emissions-weighted energy, and cost-weighted energy.It finds that the simpler methods of EUI and site energy provide the least useful information. The other methods offer useful answers to different questions, and therefore the user may need more than one of them in order to make justified decisions on energy efficiency.

Date Published



Buildings - Energy Efficiency

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