EUI Calculator (Energy Use Intensity)

Energy Use Intensity (EUI) is a metric that measures how much energy a building consumes relative to its size. It is calculated by dividing the total annual energy consumption (in kBtu) by the total floor area (in square feet). 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 sum all energy sources — electricity, natural gas, fuel oil, propane, steam, and chilled water — converting each to kBtu before dividing by the building's gross floor area.

Typical EUI values vary widely by building type. Offices average around 50–90 kBtu/ft²/yr, schools around 50–70, hospitals can exceed 200–400, warehouses are often below 30, and retail stores typically fall between 50–100. Energy Star certified buildings generally score in the top 25% for their type.

EUI provides a standardized way to compare the energy performance of buildings regardless of their size. It helps property owners, engineers, and policymakers identify inefficient buildings, track improvements over time, and set targets for energy reduction. Many green building certifications and local benchmarking laws use EUI as a primary metric.

Site EUI measures the energy consumed directly at the building, while source EUI accounts for the total energy required to produce and deliver that energy, including transmission losses. Source EUI gives a more complete picture of a building's total environmental impact. Energy Star typically uses source EUI for its benchmarking scores.

Electricity is converted using the factor: 1 kWh = 3.412 kBtu. So if a building consumes 100,000 kWh per year, that equals approximately 341,200 kBtu. This conversion is necessary to add electricity to other fuel types, which are often already measured in kBtu or can be easily converted.

A good target depends on your building type, climate zone, and operational hours. Generally, an EUI significantly below the median for your building type is considered good performance. Net-zero energy buildings aim for an EUI low enough that on-site renewable generation can offset it entirely — often below 20–30 kBtu/ft²/yr for offices.

Yes — that is precisely why EUI is so useful. Because it normalizes energy consumption by floor area, a 1,000 ft² office and a 500,000 ft² skyscraper can be meaningfully compared. However, for fair comparisons, buildings should ideally be of the same type and in similar climate zones, since both factors heavily influence energy needs.