What Is Energy Use Intensity (EUI)?

Energy Use Intensity refers to the rate of energy use in a building each year in relation to its total floor area. It is normally measured in thousands of British thermal units per square foot per year (kBtu/ft²/yr).

EUI makes comparison between buildings much easier because, unlike an energy bill, it accounts for building size. Owners and managers can use it to benchmark similar properties, identify areas where energy is being wasted, and track the results of efficiency improvements. A higher EUI generally indicates a less energy-efficient building.

Why EUI Matters for Building Owners

EUI is more than a reporting figure. It helps property owners and managers identify poorly performing buildings within a portfolio, establish a baseline for efficiency improvements, and support benchmarking obligations. Local benchmarking regulations also make accurate building energy data important for annual reporting.

The EUI Formula

At its core, calculating EUI is a straightforward division, but accurate inputs matter.

The basic formula is:

EUI = Total Annual Energy Consumption (kBtu) ÷ Gross Floor Area (ft²)

You need two key pieces of information: the building's total energy use over a 12-month period and its total square footage. Dividing annual energy use by gross floor area gives the building's EUI.

Units Used in EUI Calculations

Energy use is converted to kBtu for calculating EUI. This allows electricity, natural gas, steam, and other fuel sources to be combined using a common unit. Floor area is measured in square feet, resulting in an EUI expressed in kBtu/ft²/yr.

How to Calculate EUI Step by Step

Calculating EUI becomes easier when it is broken into a consistent sequence.

Step 1: Gather Your Annual Energy Use Data

Gather 12 months of utility data for every fuel source used by the building, including electricity, natural gas, steam, and fuel oil where applicable. The data should be complete and cover the same reporting period.

Step 2: Convert Energy Use to kBtu

Fuel sources are measured differently. Electricity may be reported in kilowatt-hours and natural gas in therms, so convert each source to kBtu using the applicable conversion factors before adding the totals together.

Step 3: Get Your Building's Gross Floor Area

Calculate the total gross floor area of the building in square feet. Use the area definition required by your benchmarking program and make sure it matches the property and occupancy information in your reporting system.

Step 4: Divide Total Energy Use by Floor Area

Divide total annual energy consumption in kBtu by gross floor area in square feet. The result is the building's EUI in kBtu/ft²/yr.

EUI Calculation Example

If a building consumes 500,000 kBtu in one year and has a gross floor area of 10,000 square feet, its EUI is:

500,000 kBtu ÷ 10,000 ft² = 50 kBtu/ft²/yr

Site EUI vs. Source EUI

Not all EUI figures are calculated the same way, and understanding the difference matters when comparing results.

What Is Site EUI?

Site EUI reflects the amount of energy consumed at the building itself, as recorded on utility bills. It is a direct measure of what the building uses on site.

What Is Source EUI?

Source EUI accounts for the energy required to generate and deliver energy to the building, including losses during generation, transmission, and distribution. It is generally higher than Site EUI, particularly for electricity.

Which One Should You Use?

Site EUI is useful for straightforward energy tracking and cost analysis. Source EUI is commonly used for benchmarking and comparing environmental impact because it accounts for the full energy chain. EPA Portfolio Manager typically uses Source EUI for ENERGY STAR scoring.

Average EUI by Building Type

EUI benchmarks vary significantly by building type because energy needs differ by use.

Office buildings: Energy use depends on HVAC systems, operating hours, occupancy, and equipment density.
Multifamily and residential buildings: EUI can vary based on building age, insulation, heating systems, and the way utilities are metered.
Retail and other commercial buildings: Extended operating hours, refrigeration, and lighting can result in higher EUI values.

How EnergiDash Simplifies EUI Calculation

The EUI formula is simple, but gathering accurate data across multiple buildings and fuel types can be time-consuming. EnergiDash removes much of that manual effort.

Automatic EUI Tracking

EnergiDash automatically calculates EUI using connected utility data, reducing the need to manually gather bills and perform conversions.

Portfolio-Wide EUI Comparison

Organizations managing multiple properties can compare EUI across an entire portfolio and identify which buildings need attention. Portfolio energy data management keeps those comparisons connected to the underlying property data.

Sync EUI Data to EPA Portfolio Manager

EnergiDash syncs EUI and related energy data directly to EPA Portfolio Manager, helping keep benchmarking records accurate without duplicate data entry. Learn more about ENERGY STAR Portfolio Manager reporting software.

Frequently Asked Questions

How do I calculate EUI manually?

Divide total annual energy consumption in kBtu by gross floor area in square feet. The result is expressed in kBtu/ft²/yr.

What is a good EUI score?

A good EUI depends on building type and location. Comparing a building with similar properties through EPA Portfolio Manager provides the most useful context.

What's the difference between EUI and ENERGY STAR score?

EUI is a raw measure of energy consumption per square foot. An ENERGY STAR score compares a building's performance against similar buildings nationwide on a 1-to-100 scale, accounting for factors such as climate and operating hours.

Does building type affect EUI?

Yes. Energy needs vary widely between offices, hospitals, retail properties, and residential buildings, so EUI should be compared within similar property categories.

Can EnergiDash calculate EUI automatically?

Yes. EnergiDash calculates EUI from connected utility data and keeps the related benchmarking information organized for review.

Calculate Your Building's EUI with EnergiDash

Knowing how to calculate EUI is a valuable first step, but managing it across an entire portfolio does not have to be manual. EnergiDash automates EUI tracking and syncs data with EPA Portfolio Manager, helping keep benchmarking records accurate. Request an EnergiDash demo to see how the workflow can support your buildings.

How to Calculate EUI (Energy Use Intensity)