Formula & Calculator
Building Energy Use Intensity (EUI)
Normalizes a building's total annual energy consumption by its floor area, allowing energy performance comparisons between buildings of different sizes.
Interpretation
EUI = Total Annual Energy Use / Building Floor Area. The energy consumed per unit floor area. Used to benchmark and improve building energy efficiency.
Variables
| Symbol | Quantity | Unit |
|---|---|---|
| EUI | Energy use intensity | kWh/m2/year |
| Total Annual Energy Use | Total annual site energy consumption | kWh/year |
| Building Floor Area | Total conditioned floor area | m2 |
What it means
Energy Use Intensity (EUI) is a key metric for building energy performance, expressed as the total annual energy consumption (in kWh or GJ) divided by the building floor area (in m² or ft²). It allows comparison of energy efficiency across different buildings and helps identify opportunities for improvement. Lower EUI means better energy performance. EUI is used in building codes, green building certifications (LEED), and energy audits. Example: An office building of 10,000 m² consumes 500,000 kWh/year. EUI = 500,000 / 10,000 = 50 kWh/m²/year. This can be compared to benchmarks for similar buildings; if above average, energy‑saving measures may be implemented, such as improved insulation, LED lighting, or efficient HVAC.
Worked example
Building Energy Use Intensity – Two Examples
Real‑World| Parameter | Value |
|---|---|
| Energy use | 500,000 kWh/yr |
| Floor area | 5,000 m² |
| Parameter | Value |
|---|---|
| Energy use | 150,000 |
| Floor area | 2,000 |
Common mistakes
- Total annual energy use: The total energy consumed by the building over a year – in kWh, MBtu, etc.
- Building floor area: The gross floor area (or net conditioned area) – in m² or ft².
- Units: EUI is expressed as kWh/m²/year or kBtu/ft²/year.
- Benchmarking: Compare EUI to similar building types (e.g., offices, schools) for energy performance assessment.
- Energy sources: EUI may be site energy or source energy – specify which.
Applications
Building energy use intensity (EUI) is the total annual energy consumed by a building divided by its gross floor area, typically expressed as kWh/m²/year. It is a key metric for benchmarking energy performance, identifying efficiency improvement opportunities, and tracking progress over time. Architects, building engineers, and facility managers use EUI to compare buildings of similar type and climate, to set energy reduction targets, and to achieve green building certifications (e.g., LEED, ENERGY STAR). Low EUI indicates better energy efficiency. By monitoring EUI, professionals can identify under‑performing systems, prioritise retrofits, and demonstrate compliance with energy codes and standards.
- Benchmarking of commercial, institutional, and residential buildings
- Energy audits and identification of efficiency measures
- Green building certification and disclosure programmes
- Tracking of energy performance improvements over time
- Policy development for building energy codes and targets
Frequently Asked Questions
EUI is the energy consumption per unit floor area of a building. It is calculated as EUI = Total Annual Energy Use / Building Floor Area. The units are typically kBtu/ft²/year or kWh/m²/year.
Comparing EUI across buildings with very different uses (data centers vs offices vs warehouses) without normalising for building type. Energy‑intensive equipment loads vary greatly. Use building‑type‑specific benchmarks for fair comparison.
- Office buildings: 50‑100 kBtu/ft²/year (150‑300 kWh/m²/year).
- Hospitals: 200‑300 kBtu/ft²/year.
- Schools: 50‑80 kBtu/ft²/year.
- Data centers: 300‑600 kBtu/ft²/year.
- Warehouses: 20‑40 kBtu/ft²/year.
EUI = 500,000 / 10,000 = 50 kWh/m²/year. In kBtu/ft², using conversion: 50 kWh/m² × 0.317 = 15.85 kBtu/ft² (approx).
EUI allows benchmarking of a building's energy performance against similar buildings, identifying opportunities for energy savings, and tracking improvements over time. It is used in energy audits and green building certifications (e.g., LEED).
- Building age and envelope efficiency (insulation, windows).
- HVAC system efficiency.
- Lighting and plug loads.
- Occupancy schedules.
- Climate (heating and cooling degree days).
- Building use and operating hours.
- Upgrade insulation and windows.
- Install energy‑efficient HVAC and lighting.
- Implement energy management systems (EMS).
- Use renewable energy (solar panels).
- Optimise operational schedules.
Site EUI is the energy consumed at the building (kWh). Source EUI includes the energy lost in generation and transmission of electricity (source energy). Source EUI is used for some benchmarking programs and is higher than site EUI (by a factor depending on the grid).
LEED, BREEAM, and other certifications require a certain performance relative to benchmarks. EUI below the median (or better) earns points. It is also used for ENERGY STAR rating.
- Does not account for building use intensity (occupant density, operating hours).
- Does not differentiate between energy sources (electricity vs gas).
- May mask sub‑system inefficiencies.