Enter the total energy consumed per year and the total gross floor area into the calculator to determine the energy use intensity (EUI).

EUI Formula

The following formula is used to calculate the energy use intensity.


  • Where EUI is teh energy use intensity (GJ/Ft^2)
  • TE is the total annual energy consumption of a building (GJ or kBtu)
  • TFLA is the total floor area of the building (ft^2 or m^2)

EUI Definitoin

What is EUI?

EUI, short for energy use intensity, is a measure of the total energy per unit of area that a building consumes on an annual basis.

The energy is typically measured in units of gigajoules (GJ) kBtu. The area units are most often square feet or square meters.

Example Problem

How to calculate EUI?

  1. First, determine the total energy usage for the building for the entire year.

    For this example, the building in question uses a total of 5,000 GJ of energy per year.

  2. Next, determine the total floor area of the building.

    This will be equal to the sum of the floor area of every story in the building. For this example, there are 10 floors with an average floor area of 2,000 square ft (ft^2). This yields 20,000 square feet of floor area.

  3. Finally, calculate the EUI.

    Using the formula above the energy usage index is calculated to be:
    EUI = TE / TFLA
    EUI = 5,000 GJ/ 20,000 ft^2
    EUI = .25 GJ/ft^2