EUI Calculator (energy use intensity: site & source kBtu/ft², kWh/m²)

Understanding the energy use intensity (EUI) calculator — concept and principle

This calculator works out a building's energy use intensity, its yearly energy use per unit of floor area, from a year of electricity, gas, propane and heating-oil bills. EUI lets you compare buildings of different sizes, track savings over time and benchmark against similar buildings, in the way ENERGY STAR Portfolio Manager does.

Energy per square foot: with the default inputs the result is 41.3 kBtu/ft² (site EUI ≈ 130 kWh/m²).

How it is calculated

Each fuel is converted to kBtu: 1 kWh = 3.412, 1 therm = 100, 1 US gallon of propane = 92, 1 gallon of No. 2 oil = 138.
Site energy = sum of those kBtu.
Source energy = site energy of each fuel × its US site-to-source ratio: grid electricity 2.80, natural gas 1.05, propane and fuel oil 1.01.
Site EUI = site energy ÷ floor area (ft²); source EUI likewise. Floor area in m² is converted with 1 ft² = 0.09290304 m².
Site EUI in kWh/m² = site kBtu ÷ 3.412 ÷ floor area in m².

The principle

Dividing by floor area removes the effect of size, so a large and a small home can be compared on the same footing. Site energy is what your meters record. Source energy adds the losses in producing and delivering that energy: generating and transmitting electricity loses much more than piping gas, so electricity carries a larger ratio. Using source energy makes buildings with different fuel mixes comparable in terms of total energy drawn from primary resources. A full year of bills evens out seasonal swings in heating and cooling.

Worked example

Default inputs: 2,200 ft², 10,500 kWh electricity, 550 therms gas, no propane or oil.

Electricity = 10,500 × 3.412 = 35,826 kBtu; gas = 550 × 100 = 55,000 kBtu.
Site energy = 90,826 kBtu; site EUI = 90,826 ÷ 2,200 = 41.3 kBtu/ft².
In metric: 90,826 ÷ 3.412 = 26,620 kWh ÷ 204.4 m² = 130 kWh/m².
Source = 35,826 × 2.80 + 55,000 × 1.05 = 158,063 kBtu; source EUI = 71.8 kBtu/ft².
Electricity share = 35,826 ÷ 90,826 = 39.4%.

Each point is the calculator re-run with only “Gross floor area” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Gross floor area	Site EUI (kBtu/ft² per year)
550	165.1
1,100	82.6
1,650	55
2,200	41.3
2,750	33
3,300	27.5
4,400	20.6

How to read the result

Lower is better for the same type of building and climate. Compare your EUI with your own past years after upgrades, and with similar buildings in a similar climate. A cold climate, electric heating or a home-based business can all raise EUI without poor efficiency. Commercial benchmarks differ greatly by building type, so compare like with like.

Common mistakes

Using less than 12 months of bills.
Using heated floor area for one building and gross floor area for another.
Comparing site EUI of an all-electric building with source EUI of another.
Forgetting fuels delivered in bulk, such as oil or propane.

Keep in mind: The source ratios are US national values; other countries use different factors. The result is a benchmark, not an energy audit.

Frequently asked questions

What is a good EUI for a home?

It depends on climate and building type; compare with similar homes in your area and with your own past years.

What is the difference between site and source EUI?

Site counts the energy at your meters; source adds generation and delivery losses.

How do I convert kBtu/ft² to kWh/m²?

Multiply by about 3.155 (1 kBtu = 0.2931 kWh and 1 ft² = 0.0929 m²).

Sources: ENERGY STAR Portfolio Manager Technical Reference: Thermal Energy Conversions (2015) · ENERGY STAR Portfolio Manager Technical Reference: Source Energy (2023)

Checked 9 Nov 2026. ENERGY STAR Portfolio Manager Technical Reference: Thermal Energy Conversions (Aug 2015; kWh 3.412, therm 100, propane gal 92, No. 2 oil gal 138 kBtu) and Source Energy (Aug 2023; US ratios: grid electricity 2.80, natural gas 1.05, fuel oil and propane 1.01). The default bills are an example home.

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