EUI (Energy Use Intensity) Calculator

Energy Use Intensity (EUI) is a metric that measures the energy efficiency of a building by dividing its total annual energy consumption by its total gross floor area. It is typically expressed in kBtu per square foot per year (kBtu/ft²/yr). A lower EUI indicates a more energy-efficient building.

EUI is calculated using the formula: EUI = Total Annual Energy Consumption (kBtu) ÷ Total Floor Area (ft²). You first convert all energy sources — electricity, natural gas, fuel oil, propane, steam, chilled water — to a common unit (kBtu), sum them up, then divide by the building's gross conditioned floor area.

EUI provides a standardized way to benchmark and compare the energy performance of buildings regardless of size or type. It helps building owners, managers, and energy auditors identify inefficiencies, set reduction targets, and track progress over time. It is also a key metric used in programs like ENERGY STAR and LEED certification.

EUI varies widely by building type. A high-performing office building may have an EUI around 30–50 kBtu/ft²/yr, while a hospital or data center can exceed 300 kBtu/ft²/yr due to intensive 24/7 operations. The U.S. national median EUI for office buildings is approximately 90 kBtu/ft²/yr. Always compare your EUI against benchmarks for your specific building type.

Site EUI measures the energy consumed directly at the building, while Source EUI accounts for all energy losses during generation, transmission, and distribution. Source EUI provides a more complete picture of a building's total environmental impact. ENERGY STAR uses Source EUI for its building rating system.

Common conversion factors are: 1 kWh of electricity = 3.412 kBtu; 1 therm of natural gas = 100 kBtu; 1 gallon of fuel oil (#2) = 138.69 kBtu; 1 gallon of propane = 91.47 kBtu; 1 lb of steam ≈ 1.194 kBtu; 1 ton-hour of chilled water = 12 kBtu. This calculator handles all conversions automatically.

A good EUI depends on your building type and climate. As a general rule, buildings targeting net-zero energy aim for an EUI below 20–30 kBtu/ft²/yr. The U.S. Department of Energy's Zero Energy Ready Home program and ASHRAE 90.1 provide specific benchmarks by occupancy type. Comparing against peer buildings of the same type in the same climate zone gives the most meaningful assessment.

Common strategies to lower EUI include upgrading HVAC systems, improving building envelope insulation and air sealing, switching to LED lighting, optimizing building controls and automation, installing renewable energy systems, and conducting regular energy audits. Even behavioral changes like adjusting set-point schedules can meaningfully reduce energy use intensity.