Energy use intensity lets you compare the energy performance of buildings of different sizes. A lower EUI means better performance. ENERGY STAR Portfolio Manager publishes median EUIs for many building types, which give a useful benchmark.
How to use the EUI Calculator
- Annual energy use
- Gross floor area
- Building type (median site EUI, kBtu/ft²)
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the total energy the building used in a year (add electricity, gas and other fuels converted to the same unit), the gross floor area and the building type.
Tips
- Use the figures from your own bills and product labels – prices and appliance ratings vary widely.
- Look at yearly totals: small daily costs add up and make it easier to compare options.
- Round quantities up to whole packs, rolls or bulbs when you shop.
- Re-check the numbers when prices change; most results scale directly with the unit price.
Common mistakes to avoid
- Confusing watts (power) with watt-hours or kilowatt-hours (energy).
- Comparing prices without bringing them to the same unit first.
- Ignoring one-off costs such as installation, delivery or replacement parts.
Inputs explained
| Field | What to enter |
|---|---|
| Annual energy use | Units: kBtu, kWh, MWh, therms, GJ |
| Gross floor area | Units: ft², m² |
| Building type (median site EUI, kBtu/ft²) | Choose one: Office (52.9), Hotel (63.0), K-12 school (48.5), Hospital (234.3) … |
What each result means
- Energy use intensity = [Annual energy use]÷[Gross floor area]
- Compared with national median = ([Energy use intensity]÷[Building type (median site EUI, kBtu÷ft²)] – 1)×100
Example values
How the main result changes when Annual energy use changes and everything else stays at the example values above:
| Annual energy use (kBtu) | Energy use intensity (kBtu/ft²/yr) |
|---|---|
| 100,000 | 10 |
| 150,000 | 15 |
| 200,000 | 20 |
| 250,000 | 25 |
| 300,000 | 30 |
| 400,000 | 40 |
Formula
Site EUI = total annual site energy ÷ gross floor areakBtu/ft² = kWh/ft² × 3.412; kWh/m² = kBtu/ft² × 3.155Worked example
Inputs — Annual energy use: 200,000 kBtu; Gross floor area: 10,000 ft²; Building type (median site EUI, kBtu/ft²): Office (52.9).
Results — Energy use intensity = 20 kBtu/ft²/yr; Compared with national median = -62 %.
Key terms
- EUI
- Energy use intensity – annual energy divided by floor area.
Frequently asked questions
What is a good EUI for an office?
The U.S. median for offices is about 53 kBtu/ft² per year; high performers are under 35.
What is the difference between site and source EUI?
Site EUI counts energy used on site; source EUI includes losses in generating and delivering it.
How do I convert kWh to kBtu?
Multiply by 3.412.
What formula does the EUI Calculator use?
Site EUI = total annual site energy ÷ gross floor area.