Energy Use Intensity (EUI) Calculator

Energy Use Intensity normalizes a building's annual energy consumption by its gross floor area, expressed in the United States as thousand Btu per square foot per year and elsewhere as kilowatt hours per square metre. All fuels are converted to a common unit before dividing: electricity at 3.412 kBtu per kilowatt hour and natural gas at 100 kBtu per therm. Site EUI counts energy as delivered at the meter. Source EUI adds the generation and transmission losses upstream, applying a multiplier near 2.8 for grid electricity and close to 1.05 for natural gas, so an all-electric building looks better on site EUI and worse on source EUI than an equivalent gas-heated one. Interpretation is by comparison with peers. Median site EUI in US commercial stock is roughly 50 to 80 kBtu per square foot for offices, retail and schools, near 30 for unrefrigerated warehouses, around 90 to 100 for hotels, and far higher for process-driven types, with hospitals near 250 and full service restaurants above 400. A ratio below about half the peer median is exceptional, and above about 1.25 times it indicates a real problem. The caveats are substantial: EUI is not weather normalized, so the same building scores differently in Minneapolis and Phoenix; it is sensitive to how gross floor area is defined, including whether unconditioned parking and mechanical space count; and it ignores operating hours, occupant density and plug load intensity, all of which can legitimately double the figure for a well-run building.

Building energy benchmarking became possible only when there was a statistically valid picture of the existing stock. The US Energy Information Administration began the Commercial Buildings Energy Consumption Survey in 1979, in the aftermath of the oil shocks, and has repeated it periodically since; it is the source of the peer medians against which almost every American EUI figure is judged. The intensity metric itself, energy divided by floor area, was already used by engineers and by the energy conservation standards work that produced ASHRAE Standard 90 in 1975, but the survey gave it a denominator drawn from real buildings. The Environmental Protection Agency launched ENERGY STAR in 1992 and extended it to whole buildings later in the decade, releasing the Portfolio Manager benchmarking tool in 1999 with a 1 to 100 score derived from survey regression models rather than raw EUI, precisely because raw EUI ignores climate and operating characteristics. Mandatory disclosure followed: New York City adopted Local Law 84 in 2009 requiring annual benchmarking of large buildings, and dozens of US cities and several states enacted comparable ordinances over the following decade. More recent building performance standards, including New York City Local Law 97 of 2019, moved beyond disclosure to enforceable intensity limits, which is why EUI has shifted from an engineering diagnostic to a compliance number with financial consequences.