One Building, Two Fuels, One Number in kBtu per Square Foot
Benchmarking a commercial building means answering a single question: how much energy does this property use for its size? Getting there is arithmetic before it is analysis, because the electric meter counts kilowatt-hours and the gas meter counts therms, and nothing can be compared until both sit in the same unit. Benchmarking tools settle that by pulling every fuel into thousands of British thermal units — kBtu — and dividing the total by gross floor area to give site energy use intensity.
Three Conventions Behind Every Reported Figure
Every Fuel Lands in the Same kBtu Column
Source EUI Rescales the Electric Half
The 1–100 Score Is a Percentile, Not a Grade
Building an EUI From a Year of Electricity and Gas
The order matters more than the arithmetic: gather twelve full months first, convert second, divide last.
Total twelve consecutive months on every meter
Bills rarely land on calendar months, so align the electric and gas periods as closely as the statements allow and note the end date you used. A partial year quietly understates a heating-dominated property and flatters a cooling-dominated one.
Convert the electricity side
Type the annual kilowatt-hours and read the therm equivalent as you type, or multiply the same figure by 3.412 for kBtu directly. Both fields stay live, so a corrected meter total updates the other side immediately.
Add the gas kBtu and divide by gross floor area
Gas is the easy half: therms × 100 is kBtu with no rounding at all. Add it to the electric kBtu and divide by gross floor area — everything inside the exterior walls, including corridors, plant rooms and unoccupied space.
Reverse the arrows to test a therm reduction target
When a retrofit is quoted as therms saved, the swap control puts therms on the left so you can see the kilowatt-hours it stands for — the number you need when the same load is about to move onto the electric meter.
Site EUI for Mixed-Fuel Buildings by Property Type
Each row converts a year of metered electricity at 3.412 kBtu per kilowatt-hour and a year of gas at 100 kBtu per therm, then divides the combined total by gross floor area. The consumption figures are typical rather than measured, chosen so each EUI lands close to the published US median for that property type.
| Property type | Floor area (ft²) | Electricity (kWh/yr) | Gas (therms/yr) | Electric (kBtu) | Gas (kBtu) | Site EUI |
|---|---|---|---|---|---|---|
| Warehouse, unrefrigerated | 120,000 | 350,000 | 12,000 | 1,194,200 | 1,200,000 | 20.0 |
| K-12 school | 70,000 | 600,000 | 14,000 | 2,047,200 | 1,400,000 | 49.2 |
| Office | 25,000 | 300,000 | 2,800 | 1,023,600 | 280,000 | 52.1 |
| Office, all-electric | 25,000 | 340,000 | 0 | 1,160,080 | 0 | 46.4 |
| Hotel | 90,000 | 1,200,000 | 15,800 | 4,094,400 | 1,580,000 | 63.0 |
| Hospital | 200,000 | 6,000,000 | 187,000 | 20,472,000 | 18,700,000 | 195.9 |
| Supermarket | 45,000 | 2,300,000 | 11,500 | 7,847,600 | 1,150,000 | 199.9 |
The spread is the point: a supermarket runs roughly ten times the intensity of a warehouse of the same footprint, because refrigeration and long trading hours never stop. Note the two office rows, which describe the same 25,000 ft² building before and after a fuel switch. Site EUI falls from 52.1 to 46.4 simply because the heat pumps deliver more warmth than the kilowatt-hours they consume, while every therm the old boiler burned counted at face value.
What Helps While Assembling a Benchmark
Portfolio-Sized Totals Keep Their Spacing
Annual consumption for a hospital runs to seven digits. Thousands are separated in the display, so a six-million-kilowatt-hour entry stays legible while you check it against the utility summary.
Therm Digits That Paste Into the Benchmarking Workbook
The copy control returns the bare figure without the unit or the thousands spacing, so a converted therm total drops into the cell that feeds your kBtu column. Ctrl+C in the field behaves identically.
Test a Fuel-Switch Scenario From Either Side
Reversing the direction lets you start from the therms a boiler replacement removes and see the electric equivalent, or start from a proposed kilowatt-hour budget and read back the gas it displaces.
When a Portfolio Reports in MMBtu or Gigajoules
Multi-country owners rarely file everything in therms. The searchable menus on both sides cover 24 energy units, so a Canadian site reporting gigajoules meets a US site reporting therms without leaving the page.
Benchmarking Questions Behind the EUI Number
How do electricity kilowatt-hours and gas therms end up in one EUI?
Each fuel is multiplied by its own energy content until everything is in kBtu. Electricity converts at 3.412 kBtu per kilowatt-hour, which is just the joule equivalence of a kilowatt-hour restated in British thermal units; gas converts at exactly 100 kBtu per therm, because that is how the therm is defined. Add the kBtu columns, divide by gross floor area, and the result is site EUI in kBtu per square foot. Nothing in that chain cares which fuel did which job — a kBtu of gas heating and a kBtu of lighting count identically.
Why is an all-electric building's source EUI so much higher than its site EUI?
Because generating and delivering a kilowatt-hour consumes roughly two and a half to three times its own energy content at the power station and on the wires, whereas gas burned on site loses only a few per cent getting there. Applying those weightings to the all-electric office in the table takes it from 46.4 kBtu/ft² site to around 130 source, while the mixed-fuel office beside it moves from 52.1 to roughly 126. The site figure says the electric building uses less; the source figure says the two are close. Neither is wrong — they answer different questions, and a report has to name which one it used.
What counts as a good site EUI for an office?
US office stock clusters around a median near 52 kBtu/ft², so anything in the low forties is genuinely good and the high twenties is high-performance territory. Above about 75 there is usually something structural — a data room carried on the building's meter, a ventilation system running around the clock, or single-glazed envelope. Judge against the median for your climate zone and operating hours rather than a national figure, because a 24-hour trading floor and a nine-to-five suite are not the same property type even if both call themselves offices.
Does replacing a gas boiler with heat pumps improve EUI on its own?
On site EUI, yes, and often substantially, because the heat pump only draws a third or a quarter of the energy the boiler burned to deliver identical comfort. The table's two office rows show 52.1 dropping to 46.4 with no change in temperature or occupancy. On source EUI the gain is far smaller and can vanish, since the electricity carries its generation losses with it. That gap is exactly why disclosure programmes and lenders increasingly ask for both figures, and why a project justified on site EUI alone can look disappointing when the same portfolio is scored on source.
Which floor area does the benchmark divide by?
Gross floor area measured from the outside of the exterior walls, counting every finished storey: corridors, lobbies, stairwells, plant rooms, storage and vacant space all included. Enclosed parking is normally treated separately, and unenclosed decks are excluded. Substituting rentable or usable area is the most common error in a first submission, and because it can be ten to fifteen per cent smaller it inflates EUI by the same proportion — enough to move a building several points down a percentile ranking without a single kilowatt-hour changing.
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