How this calculator works
Energy use intensity is annual energy divided by floor area, usually reported in kilowatt-hours per square metre per year. Because it removes size from the comparison, a small efficient house and a large efficient house can end up with similar values, and a poorly insulated house becomes obvious when it sits next to its neighbours. Energy here means site energy, the electricity and fuel delivered to the building, not the upstream energy used to generate it. The same year and the same area definition must be used for a fair comparison, which in practice means the conditioned floor area and a full calendar year of bills.
Formula
EUI = annual energy in kWh / conditioned floor area in m2. annual energy = EUI x area. floor area = annual energy / EUI.
Worked example
A home using 18,000 kWh of electricity and 60,000 kWh of natural gas in a year has 78,000 kWh of site energy. Over 200 m2 of conditioned floor area that is 390 kWh/m2 per year. The same home at 200 m2 but with an EUI of 450 kWh/m2 would need 90,000 kWh for the year.
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Frequently asked questions
Which energy should I count?
Count every metered source delivered to the home for a full year: electricity, natural gas, propane, heating oil and wood. Combining fuels is simplest in kWh; convert other units with the supplier energy content and state what you used.
Should a garage or basement be included?
Include only conditioned space, the area that is heated and cooled. Counting an unheated garage makes the home look better than it is, and leaving out a finished basement makes it look worse.
What is a typical EUI in Canada?
It varies widely by region, home age and fuel mix, so a single national number is misleading. Compare against similar homes in your province, or track your own value from year to year after an upgrade.
Is EUI the same as an EnerGuide rating?
No. EnerGuide ratings for homes come from a modelled assessment and are reported on a different scale. EUI is a simple metered ratio that you can calculate from two bills and a floor plan.