How to Calculate EUI (Energy Use Intensity)
Unlock insights into your building's energy consumption. Learn to effectively measure and evaluate its Energy Use Intensity (EUI).
Energy Use Intensity (EUI) serves as a metric for evaluating a building’s energy performance. This standardized measurement helps property owners and managers understand how efficiently their buildings consume energy relative to their size. It provides a consistent benchmark, facilitating informed decision-making regarding energy management and potential improvements.
What is Energy Use Intensity (EUI)
Energy Use Intensity (EUI) quantifies a building’s annual energy consumption in relation to its gross floor area. It acts as a performance indicator, similar to a “miles per gallon” rating for buildings, reflecting operational efficiency. EUI is expressed in units such as kBtu per square foot per year (kBtu/sq ft/year) or kilowatt-hours per square meter per year (kWh/sq m/year). This metric allows for benchmarking a building’s energy performance against similar types or industry averages. Understanding EUI can highlight areas of energy waste, guiding efforts to reduce consumption and support sustainability initiatives.
Essential Data for EUI Calculation
Accurately calculating EUI requires two primary pieces of information: the total annual energy consumption and the total building area. The total annual energy consumption encompasses all energy sources used by the building over a full 12-month period, including electricity, natural gas, and any other fuels. This data is found on utility bills, and all energy types must be converted into a common unit, such as British thermal units (Btus) or kilowatt-hours (kWh), before summing them. For instance, electricity might be billed in kWh, while natural gas is often measured in therms or cubic feet, necessitating conversion to a consistent unit like kBtu.
The second required data point is the total building area, which refers to the gross floor area of the conditioned space. This area includes all enclosed spaces within the building’s thermal envelope that are directly or indirectly heated or cooled. Building plans, property records, or previous appraisals are common sources for obtaining this measurement in square feet or square meters. Ensure the area calculation is comprehensive, including stairwells and elevator shafts, but excluding unconditioned spaces like exterior parking areas or open terraces.
Step-by-Step EUI Calculation
Once the necessary data is collected and converted to consistent units, calculating EUI involves a straightforward division. The formula for EUI is the total annual energy consumption divided by the total gross floor area. For example, if a building consumed 1,500,000 kBtu of energy over a year and has a gross floor area of 20,000 square feet, the calculation is as follows.
To apply this, first confirm the total annual energy consumption is in a single unit, such as kBtu, and the total gross floor area is in square feet. Then, divide the energy consumption by the area. Using the example values: EUI = 1,500,000 kBtu / 20,000 sq ft. This calculation yields an EUI of 75 kBtu per square foot per year. This standardized ratio allows for meaningful comparisons across buildings of varying sizes and energy usage levels.
Understanding Your EUI Score
The calculated EUI score provides a quantifiable measure of a building’s energy performance. A lower EUI indicates greater energy efficiency, as the building uses less energy per unit of area. The significance of an EUI score is best understood through benchmarking, which involves comparing a building’s EUI to that of similar buildings or industry averages. Building types influence EUI, with facilities like hospitals or laboratories having higher energy demands than offices or residences.
Tools like the U.S. Environmental Protection Agency’s (EPA) ENERGY STAR Portfolio Manager are widely used for benchmarking. This web-based tool allows building owners to input their energy data and receive an EUI, which can then be compared to national median EUIs for similar property types. Benchmarking helps identify if a building is performing efficiently or if it consumes more energy than comparable structures, thereby highlighting potential opportunities for energy efficiency improvements and cost reductions.