Building Energy Intensity Calculator
A building's energy use intensity — kilowatt-hours per square metre per year — from its bills and floor area, against typical bands, and what a reduction target means in energy and money.
Energy use intensity is annual energy divided by floor area.
How the building energy intensity calculator works
Energy use intensity is annual energy divided by floor area. It is the single number that lets buildings of different sizes be compared, and it is what rating schemes are built on.
An office at 100 kWh/m²/year is good; at 250 it is poor. A house at 50 is efficient; 150 is typical of older stock. The bands are broad because climate moves them, but the ranking holds.
Formula: EUI = annual energy / floor area
Worked examples
| Inputs | Energy intensity (kWh/m²/year) | Note |
|---|---|---|
| An 1,800 m² office | 113.9 | 114 kWh/m² — typical |
| An efficient house | 41.7 | efficient |
| An old retail box | 375 | very poor |
FAQFrequently asked questions
What is energy use intensity?
Annual energy per square metre of floor. It is how buildings of different sizes are compared and what most rating schemes measure.
What is a good EUI?
Under 100 kWh/m²/year for an office and under 50 for a house is efficient in most climates. Very cold or hot climates push every band up.
Should I use site or source energy?
This uses site energy — what the meter reads. Source energy weights electricity for generation losses and is what carbon accounting needs.
Where does the saving come from?
Lighting and HVAC controls first, then envelope and equipment. Thirty per cent is usually achievable in an older building without touching the fabric.
Does floor area include car parks?
Rating schemes usually exclude them. Use the conditioned or lettable area your scheme specifies; the answer changes a lot.
Where these figures come from
- Sabine (1922) — Collected Papers on Acoustics — the reverberation-time equation
- CIBSE Guide A — Environmental design — daylight, comfort and ventilation criteria
- Neufert — Architects' Data — the standard reference for space and dimension
- International Code Council — International Building Code — occupant load and egress factors
- Building Regulations — Approved Documents — the UK building regulations
Last checked: September 2026. Formulas are the standard building-science and code relationships; default thresholds are common international values and should be replaced with the ones in your code.