What Is Energy Use Intensity (EUI)?
Energy Use Intensity, or EUI, is the standard metric for expressing a building's energy consumption relative to its size. Measured in kBtu per square foot per year, it lets you compare buildings of different sizes on a level playing field. A lower EUI means better energy performance.
The U.S. Environmental Protection Agency uses EUI as the foundation for its ENERGY STAR score. Property managers, architects, and energy auditors rely on it during benchmarking exercises to spot inefficiencies. If you know your annual energy bills and your building's floor area, you already have the raw data needed to compute your EUI. For tracking expenses over time, pair this with the electricity cost calculator to see how usage translates to dollars.
EUI works for any building type — offices, schools, hospitals, warehouses, retail stores, and even single-family homes. The metric cuts through differences in fuel types by converting everything to a common unit (kBtu), so natural gas and electricity can be combined into one number. You can also convert between unit systems using the energy conversion calculator.
How EUI Is Calculated
The basic formula is straightforward: total annual energy consumed (in kBtu) divided by gross floor area (in square feet). If your utility bills report electricity in kWh and gas in therms, convert each to kBtu first — 1 kWh equals 3.412 kBtu, and 1 therm equals 99.976 kBtu. Add them together, then divide by floor area.
Gross floor area includes all enclosed spaces: basements, mechanical rooms, storage areas, and corridors. Measure the exterior dimensions of the building, beyond the occupied space. The square footage calculator can help you compute this from building dimensions. Do not exclude unheated spaces unless your benchmarking protocol specifically requires it.
Some organizations calculate EUI using only conditioned floor area, which can make the number appear lower. Be consistent with whatever convention your local code or rating system specifies. The key is using the same methodology year after year so your trend line stays meaningful.
Site EUI vs Source EUI
Site EUI counts only the energy delivered to your building — what the meter reads. Source EUI accounts for the energy lost during generation, transmission, and distribution. For electricity, the U.S. national average source-site ratio is roughly 2.8, meaning every 1 kBtu delivered to your building required about 2.8 kBtu of primary energy at the power plant.
ENERGY STAR Portfolio Manager uses site EUI for its 1 to 100 score but also tracks source EUI for reference. If your building is all-electric, your source EUI will be nearly three times your site EUI. For buildings heated by natural gas or fuel oil, the gap is smaller because those fuels have source-site ratios closer to 1.0.
When reporting EUI to stakeholders, clarify which version you are using. Many state and local benchmarking ordinances (like NYC Local Law 84, Boston BERDO, and Washington DC BEPS) require site EUI reporting. Both versions are valid metrics — they just answer different questions about energy consumption and grid losses.
Benchmarking Your Building's Performance
The real value of EUI emerges when you compare it against peer buildings. The Commercial Building Energy Consumption Survey (CBECS) publishes median EUI values by property type. For example, the median office building in the U.S. has a site EUI around 52.8 kBtu/sq ft/yr, while hospitals average over 200 due to 24/7 operation and specialized equipment.
An efficient office building might achieve an EUI of 30 or below, placing it in the top quartile. Supermarkets and restaurants tend to run high (200 to 400) because of refrigeration and cooking loads. Knowing where your building sits on this distribution tells you whether upgrades are worth pursuing.
Before investing in retrofits, conduct a thorough heat loss calculator analysis to pinpoint where energy escapes the building envelope. You can also check whether your furnace size calculator results match your actual heating capacity — oversized equipment short-cycles and wastes fuel. For cooling loads, the AC tonnage calculator provides similar guidance on right-sizing.
Factors That Affect EUI
Climate is the single biggest driver of EUI variation. A building in Minneapolis will always use more energy than an identical one in San Diego because of heating demand. The International Energy Conservation Code (IECC) climate zone map divides the U.S. into eight moisture-designated regions, each with different envelope and mechanical requirements.
Building age matters too. Pre-1980 buildings often have single-pane windows, minimal wall insulation, and atmospheric combustion equipment — all of which push EUI upward. Retrofitting with proper insulation calculator recommendations can cut heating and cooling loads by 30 to 50%. Air leakage through the building shell is another major factor, measurable with the air changes per hour calculator.
Occupant behavior and operating schedules also shift EUI significantly. A building running servers 24/7 will have a baseload that dwarfs lighting upgrades. Start by auditing your appliance wattage calculator results to identify the biggest energy consumers. Plug loads from computers, monitors, and kitchen equipment often account for 20 to 30% of total consumption in office environments.
Reducing Your Building's EUI
Lowering EUI follows a standard hierarchy: reduce loads first, then improve system efficiency, then consider renewable energy. Load reduction means better insulation, air sealing, and high-performance windows. System efficiency means upgrading to LED lighting, variable-speed HVAC, and high-efficiency boilers or heat pumps.
After implementing upgrades, monitor EUI for at least 12 months to verify savings. Weather-normalize the data using heating degree days and cooling degree days so year-to-year comparisons remain fair. Utility bill tracking is the simplest method, but sub-metering specific zones or systems gives more granular feedback.
For buildings with high electricity consumption, on-site solar can offset purchased energy and lower your reported EUI. Many states offer performance incentives based on verified kWh savings rather than installed capacity. If you want to estimate the environmental benefit of efficiency upgrades, the carbon equivalent calculator converts energy savings into CO2 reductions.
EUI Reporting and Compliance
Over 40 U.S. cities and states now require annual energy benchmarking for commercial buildings, typically using ENERGY STAR Portfolio Manager. These ordinances trigger at thresholds like 50,000 sq ft (New York, San Francisco, Seattle) or 25,000 sq ft (Boston, Cambridge). The reported metric is almost always site EUI, submitted by June 1 of each year.
Building Performance Standards (BPS) go further by setting EUI targets that buildings must meet or face penalties. Washington DC's BEPS requires buildings to achieve a site EUI at or below their peer-group median by 2030. Colorado's BPS targets a 7% EUI reduction by 2026 and 4% more by 2030.
Staying compliant means tracking EUI continuously, beyond reporting time. Many facilities teams set up monthly utility tracking dashboards and review EUI trends quarterly. This proactive approach catches drift in HVAC controls, equipment malfunctions, and behavioral changes before they inflate annual totals.
Common EUI Values by Building Type
Representative median site EUI values from CBECS and ENERGY STAR data: offices approximately 53, K-12 schools around 47, hospitals near 228, retail stores about 73, hotels near 94, warehouses roughly 16, supermarkets close to 340, and restaurants around 290 kBtu/sq ft/yr. These are national medians — actual values vary by climate, vintage, and operating hours.
High-performance buildings routinely beat these numbers by 30 to 50%. A LEED Platinum office might achieve an EUI of 25 to 30, while a Passive House building could reach single digits in a mild climate. Net-zero energy buildings, which produce as much energy as they consume through on-site renewables, report an EUI of zero (or negative) on a net basis.
Use these benchmarks as conversation starters with building owners and facility managers. If your building is well above the median for its type, there is significant room for improvement. If you are already below median, incremental gains become harder and may require deeper retrofits or controls optimization.