Building Energy Use Intensity (EUI
### Building Science & HVAC: Energy Use Intensity (EUI) Energy Use Intensity (EUI) is the fundamental standard metric used by architects, MEP engineers, and the US Department of Energy to benchmark.
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📐 Formula
💡 Practical Example
For example, evaluating a \(50,000\text{ ft}^2\text{ commercial office building}\) consuming \(750,000\text{ kWh}\) of electricity (\(2,559,105\text{ kBTU}\)) and \(12,000\text{ therms}\) of natural gas (\(1,200,000\text{ kBTU}\)) at \ and \: Total site energy is \}}\). Site EUI is \. Source EUI is 168.51 kBTU/ft²/yr. Total utility bill is \ Energy Cost Intensity), running \(41.9\%\) above the commercial office CBECS median).
📖 About Building Energy Use Intensity (EUI
Building Science & HVAC: Energy Use Intensity (EUI)
Energy Use Intensity (EUI) is the fundamental standard metric used by architects, MEP engineers, and the US Department of Energy to benchmark building energy efficiency:
- Site EUI vs. Source EUI:
- Site EUI: The actual amount of heat and electricity metered directly at the building boundary per unit area per year.
- Source EUI: Factors in the upstream raw fuel generation, thermal efficiency, and transmission losses required to deliver energy to the building.
- Commercial Building Energy Consumption Survey (CBECS): Published by the US Energy Information Administration (EIA), providing national median EUI benchmarks by property type and climate zone.
- Energy Cost Intensity (ECI): Expresses total energy expenditure normalized on a \/sq.ft/year basis, allowing facility managers to evaluate energy savings against commercial lease rates.
How to Use This Calculator
Enter your Gross Conditioned Floor Area (Square Feet) (e.g. 50,000), Annual Electricity Consumption (kWh/Year) (e.g. 750,000), Annual Natural Gas Consumption (Therms/Year) (e.g. 12,000), Building Property Type (ASHRAE / CBECS) — choose from Commercial Office (Median Site EUI: ~53 kBTU/ft²), K-12 School (Median Site EUI: ~48 kBTU/ft²), Retail Store (Median Site EUI: ~58 kBTU/ft²), Electricity Utility Rate (/kWh) (e.g. 0.14), and Natural Gas Utility Rate (/Therm) (e.g. 1.20). Verify your units match the formula standard (SI vs imperial) before entering values.
The Formula
Building Energy Performance (ASHRAE \& EPA Energy Star Portfolio Manager) equations:
Total Site Energy (kBTU) = (Electricity kWh × 3.41214) + (Natural Gas Therms × 100)
Site EUI = (Total Site Energy (kBTU)) / (Gross Floor Area (ft^2)) (kBTU/ft^2/year)
Source EUI = ((Elec kBTU × 2.80) + (Gas kBTU × 1.05)) / (Gross Floor Area (ft^2))
Energy Cost Intensity (ECI) = (Total Annual Utility Spend (\)) / (Gross Floor Area (ft^2)) (\/ft^2/year)
Worked Example
For example, evaluating a 50,000 ft^2 commercial office building consuming 750,000 kWh of electricity (2,559,105 kBTU) and 12,000 therms of natural gas (1,200,000 kBTU) at \ and Total site energy is . Site EUI is \. Source EUI is 168.51 kBTU/ft²/yr. Total utility bill is \ Energy Cost Intensity), running 41.9\% above the commercial office CBECS median).
Understanding Your Result
Energy unit conversions: 1 kWh = 3,600,000 J (3.6 MJ), 1 kcal (food calorie) = 4,184 J, 1 BTU = 1,055 J. Power benchmarks: LED bulb 8–10 W, laptop 15–60 W, desktop PC 200–500 W, hair dryer 1,000–1,800 W, electric vehicle charger (Level 2) 7,200 W. A 100W device running 10 hours uses 1 kWh. At 15 cents/kWh (US average), that's 0.
- Energy efficiency is typically more cost-effective than energy generation — 1 unit of energy saved often costs 3–5× less than 1 unit generated.
💡 Methodological Standards & Calculation Accuracy
- All calculations are performed client-side in your browser using verified, standards-compliant mathematical algorithms.
- Results are provided for educational and informational analysis; verify critical applications with certified domain specialists.
- Ensure input values are entered in consistent units matching the selector options to guarantee accurate outputs.
- Periodic recalibration is recommended whenever baseline assumptions, operating parameters, or external conditions change.
Results are for informational and educational purposes only. Always verify critical decisions with a qualified professional.