Energy use intensity (EUI), explained: the one number every building owner should track
EUI turns a building's messy energy history into a single, comparable number. Here is exactly how it is calculated, how it relates to the ENERGY STAR score, and why the data behind it is where most teams struggle.
If you only track one energy number for a building, track energy use intensity. It reduces a year of bills across every fuel into a single figure you can compare against last year, against a target, and against similar buildings.
How EUI is calculated
EUI is energy per square foot per year, expressed in kBtu per square foot. You take the total annual energy the building consumed, across electricity, gas and any other fuels, convert it to a common unit, and divide by the gross floor area. A lower EUI means the building does more with less energy.
EUI is simple arithmetic. It is only as good as the data underneath it: twelve months of consumption, every fuel, every meter, in consistent units, with the right floor area. A missing month or a wrong multiplier changes the number and every decision made from it.
EUI and the ENERGY STAR score
EUI is an absolute measure. The ENERGY STAR 1 to 100 score is a relative one: it compares your building to similar buildings nationwide and adjusts for climate and how the building is used. A score of 50 is median performance. A score of 75 or higher qualifies a building for ENERGY STAR certification, meaning it performs in the top 25 percent of its peers. EUI tells you how much energy you use per square foot; the score tells you how that stacks up.
Why teams struggle to get it right
The reason EUI is harder than it looks is data collection. To compute it correctly you need every bill, for every meter, for twelve consecutive months, normalized to the same units, tied to the correct floor area. Across a portfolio that is a lot of bills in a lot of formats, which is why so many owners either estimate or fall behind. Getting the bills structured and validated first turns EUI from an annual project into a number that is always current.
Frequently asked questions
What is a good EUI?
It depends heavily on building type and climate, which is why the ENERGY STAR score exists to compare like with like. As a rule, a lower EUI is better, and the ENERGY STAR score puts median performance at 50 and certification-eligible performance at 75 or above.
What does an ENERGY STAR score of 75 mean?
A score of 75 or higher means the building performs in the top 25 percent of similar buildings nationwide, adjusted for climate and use, and is eligible for ENERGY STAR certification.
What data do I need to calculate EUI?
Twelve consecutive months of consumption for every fuel and every meter, converted to a common unit, divided by the building's gross floor area. Missing months or incorrect meter multipliers are the most common sources of error.
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