How to Calculate Building Energy Use Intensity (EUI)
Energy Use Intensity (EUI) condenses utility bills into a normalised indicator of how efficiently a building delivers conditioned space and services. Facility managers, ESG analysts, and mechanical engineers use the metric to prioritise retrofits, satisfy disclosure ordinances, and benchmark portfolios. This walkthrough breaks the calculation into reproducible steps and embeds an interactive calculator so you can validate assumptions in real time.
We align with ENERGY STAR® Portfolio Manager conventions, emphasise defensible unit conversions, and point to complementary CalcSimpler tools—including the BTU to kWh Conversion Calculator, the Heat Pump vs. Gas Furnace Breakeven Calculator, and the Data Center PUE Calculator—to keep benchmarking auditable from data collection through investment-grade analysis.
Step 1: Assemble a twelve-month utility record across all fuels
Gather at least twelve consecutive months of electricity, gas, district energy, and on-site generation data—EUI considers total consumption. Normalising to a full year strips out seasonal noise, and recording meter identifiers plus allocation notes gives auditors a transparent trail.
Step 2: Convert every energy source into consistent thermal units
EUI is reported in thousands of British thermal units per square foot per year (kBtu/ft²·yr) and increasingly in kilowatt-hours per square metre per year (kWh/m²·yr). Multiply electricity by 3.412 to express kWh in kBtu, treat therms as 100 kBtu, scale MMBtu by 1,000, and use the BTU to Watts Calculator when unusual units appear. Cite the multipliers you adopt—consistency year over year matters more than marginal precision.
Step 3: Confirm the gross floor area eligible for benchmarking
The denominator is the conditioned gross floor area documented on drawings, BIM exports, or occupancy surveys. Include heated basements or penthouses, exclude unconditioned garages, use CalcSimpler’s area reference guide for conversions, and flag partial vacancies so you can report both gross and occupied intensities.
Step 4: Compute site EUI and convert to metric intensity
Sum the converted energy totals to obtain annual site energy in kBtu, divide by gross floor area for site EUI, then convert to kWh/m²·yr by dividing the kBtu figure by 3.412 and the area by 10.7639. Record both values with their data vintage, and use the embedded calculator—identical to the standalone EUI calculator—to automate the arithmetic.
Step 5: Interpret the intensity against benchmarks and load profiles
Interpret EUI against peer data from Portfolio Manager or ASHRAE Standard 100. Analyse weather-normalised trends, tie anomalies to diagnostics like the Air Changes per Hour Calculator, and use submetered intensities for process loads, space conditioning, and plug loads to justify targeted retrofits.
Step 6: Extend from site EUI to source energy, cost, and carbon
Many ordinances request source EUI, so multiply electricity by a regional source factor before recomputing the metric and keep those factors stable each year. Pair the results with the heat pump breakeven tool, the LCOS walkthrough, and the PUE calculator to connect load shifting, electrification, and infrastructure efficiency with intensity outcomes.
Step 7: Document governance and iterate after each retrofit
Treat EUI as part of measurement and verification: store raw data, conversion factors, occupancy adjustments, and calculator outputs, rerun the calculation after each retrofit, and pair results with the Residential Solar Payback & ROI Calculator or the LCOS calculator to frame financial narratives. Review EUI annually alongside maintenance logs and tenant feedback so quantitative benchmarks align with qualitative observations about equipment performance and demand.