EUI Calculator
Calculate building Energy Use Intensity from annual energy use and gross floor area. Enter electricity, natural gas, optional fuel oil or propane, and get site EUI in kBtu/sf/year.
Reviewed May 26, 2026. JouleIO calculators are planning tools; confirm final utility rates, equipment specs, incentives, installation bids, and safety decisions with official utility, manufacturer, installer, DOE, ENERGY STAR, EPA, IRS, or EIA sources.
1. Enter real usage
Use your actual watts, runtime, home size, miles, battery size, or appliance schedule.
2. Localize the rate
Compare national assumptions with your state, utility bill, time-of-use plan, or project quote.
3. Verify before acting
Check final prices, rebates, tax rules, and safety requirements before buying or installing equipment.
Annual Energy Inputs
Use a full 12 months of meter data. Leave fuels blank if the building does not use them.
From 12 monthly electric bills or interval-data totals.
1 therm = 100 kBtu.
No. 2 heating oil basis: 138.5 kBtu/gallon.
Propane basis: 91.452 kBtu/gallon.
Match floor area to the meters included above.
Site EUI
kBtu/sf/year
Benchmark signal
Very low site EUI
Efficient or lightly loaded building
Calculation Breakdown
| Energy source | Input | Annual kBtu | Share |
|---|---|---|---|
| Electricity | 120,000 kWh | 409,440 | 54% |
| Natural gas | 3,500 therms | 350,000 | 46% |
Total site energy
759,440 kBtu/yr
Average month
63,287 kBtu
Fuel split
46% fuel
Benchmarking Caveats
EUI is a screening metric, not a score by itself. A hospital, restaurant, grocery store, school, warehouse, multifamily building, and office can have very different normal EUI ranges.
Compare buildings with similar property type, climate, operating hours, occupancy, plug loads, commercial kitchens, data centers, EV charging, and parking treatment. For formal benchmarking, enter the same 12-month meter set and gross floor area definition in ENERGY STAR Portfolio Manager.
If the EUI looks unexpectedly high, start with missing meters, partial-year bills, gas-heated water or space heating, simultaneous heating and cooling, ventilation schedules, failed controls, and equipment that runs after hours. Then use the Energy Cost Calculator and Home Energy Audit to isolate practical fixes.
Method and Sources
- Formula: total annual site energy kBtu divided by gross floor area in square feet.
- EUI concept: ENERGY STAR describes EUI as annual energy use divided by total gross floor area, and Portfolio Manager reports both site and source EUI.
- Conversion factors: EIA Btu references use 1 kWh = 3,412 Btu, 1 therm = 100,000 Btu, No. 2 heating oil = 138,500 Btu/gallon, and propane = 91,452 Btu/gallon.
- DOE context: energy intensity tracks energy use per unit of activity and helps compare efficiency trends, but the right denominator and comparison group matter.
Frequently Asked Questions
What is EUI?
Energy Use Intensity, or EUI, is annual building energy use divided by gross floor area. In the United States it is commonly shown as kBtu per square foot per year. Lower EUI usually means lower energy intensity, but property type, hours, climate, occupancy, data centers, kitchens, labs, and parking loads can change the comparison.
What formula does this EUI calculator use?
Site EUI = annual site energy in kBtu / gross floor area in square feet. This calculator converts electricity at 3.412 kBtu per kWh, natural gas at 100 kBtu per therm, No. 2 heating oil at 138.5 kBtu per gallon, and propane at 91.452 kBtu per gallon.
Should I use site EUI or source EUI?
This page calculates site EUI because it follows the fuel that enters the building and is easy to verify from utility bills. ENERGY STAR Portfolio Manager also reports source EUI, which accounts for upstream electricity generation, transmission, and delivery losses. Use the same EUI type when comparing buildings.
What floor area should I enter?
Use gross floor area, not rentable area, unless your benchmarking program explicitly tells you otherwise. Include the conditioned and operational building space that matches the meters you entered; exclude separately metered parking energy if the parking area is not part of the benchmarking floor area.
Why does my EUI differ from an ENERGY STAR Portfolio Manager result?
Common causes include missing meters, partial-year bills, weather normalization, source EUI instead of site EUI, parking or EV charging handled separately, different gross floor area definitions, or property-use details that affect ENERGY STAR scoring.