Energy use intensity – or EUI. It has been called “the miles per gallon rating of the building industry,” but many design and construction professionals are not entirely sure how EUI is defined and what its utility is with regard to project. Below is a primer to help get anyone started.
Energy Use Intensity (EUI)
Energy Use Intensity (EUI) can be defined as the measurement of a building’s annual energy consumption relative to its gross square footage. EUI is often used to:
1. Express an existing building’s actual, metered energy consumption;
2. Convey the average annual energy use derived from a data set of similar building type and location; or
3. Communicate the anticipated energy use for a particular project based on design performance or energy modeling (sometimes, this latter use is distinguished as pEUI – for predicted).
Site EUI or Source EUI?
EUI is expressed relative to either site or source energy.
Site energy is most often referenced in the design community. In simple terms, site EUI is the energy consumed at the building site and is reflected in the utility bills paid by the owner.
Source energy is a more accurate representation of a building’s energy footprint as it considers the site energy as well as the energy lost during production, transmission, and delivery to the site.
It is also worth clarifying the distinction between net EUI and gross EUI. Net EUI is determined by comparing the gross EUI – or the annual energy consumption from all sources – to the Renewable Production Intensity (RPI).
Net EUI = Gross EUI – RPI
If the annual renewable energy production is greater than the gross energy consumption, the project is said to be net zero energy.