Commercial energy / Buyer guidance
Electricity per square foot: calculate a comparable building metric
Define the meter and floor-area boundaries, distinguish site electricity from whole-building EUI and test an original normalization example.
Define the numerator and denominator before comparing buildings
Annual electricity use divided by floor area gives a useful screening ratio only when both refer to the same boundary and period. Record the meters included, annual kWh, area definition, occupancy, operating hours and significant equipment. A landlord's common-area electric account divided by the entire building area is not comparable to a whole-building account.
ENERGY STAR explains EUI as an energy-intensity measure and distinguishes site and source metrics. An electricity-only kWh/ft² ratio is not automatically whole-building EUI, an ENERGY STAR score or a performance grade. Keep gas and other fuels visible instead of labeling electricity alone as total energy.
Build a consistent annual record
Use a complete, defined period with no overlapping or missing invoices. Identify estimated readings, tenant changes, vacancy, new equipment and area changes. If solar generation or another behind-the-meter source changes, utility purchases may no longer represent total electrical consumption. Record whether the metric is purchased electricity or total site electricity.
Compare properties with similar function and operating conditions. A refrigerated warehouse and a dry warehouse are not interchangeable peers. Within one property, a new production line can change both total use and the appropriate activity denominator. A low ratio can reflect vacancy rather than efficient operation.
Worked example: the area boundary changes the apparent result
Hypothetical property: annual electric purchases are 900,000 kWh. Gross area is 50,000 ft², giving 18 kWh/ft²-year. If someone uses only 40,000 ft² of occupied area while leaving the same whole-building electricity in the numerator, the result becomes 22.5 kWh/ft²-year.
Neither calculation is inherently wrong if clearly defined, but they answer different questions. Comparing the 18 figure to another property's occupied-area metric would be misleading. If use later falls to 810,000 kWh because one tenant vacates, the gross-area ratio becomes 16.2; that change is not proof of an efficiency project.
A benchmarking record to keep
| Record | Include |
|---|---|
| Boundary | Whole building, common area, tenant or process |
| Energy | Meter list, units and complete dates |
| Area | Gross or other defined floor area, with source |
| Conditions | Hours, occupancy, weather and major loads |
| Comparison | Same property over time or a defined peer group |
Use the result to prioritize investigation, not to prescribe a budget cut. Inspect operating schedules and equipment with the facility team. A project decision needs a more specific baseline and measurement plan than an annual ratio. The worked-example guide shows how total use and intensity can move in opposite directions.
Sources and limits
ENERGY STAR EUI definitions and benchmarking interpretation support the measurement distinctions. This guide supplies no invented industry benchmark, target score or typical savings percentage. All property figures above are independently constructed.