Energy Use Intensity (EUI) Calculator
Calculate energy use intensity euicalculator easily with our free tool. Get practical results, tips, and comparisons for everyday decisions.
Calculator
Adjust values & calculateFormula
Where EUI is Energy Use Intensity in kBtu per square foot per year, Total Energy is the sum of all energy sources converted to kBtu (electricity kWh x 3.412 + gas therms x 100), and Gross Floor Area is the total building floor area in square feet.
Last reviewed: December 2025
Worked Examples
Example 1: Office Building EUI Calculation
Example 2: Hospital Source EUI Analysis
Background & Theory
The Energy Use Intensity EUI Calculator applies the following established principles and formulas. Everyday life arithmetic underpins a vast range of routine financial and practical decisions that most adults encounter on a daily or weekly basis. At its core, consumer mathematics involves applying straightforward formulas to real-world quantities, but accuracy and convenience are essential when money is involved. Tip calculation follows the simple relationship tip = bill × rate, where rate is typically expressed as a decimal (0.15 for 15%, 0.20 for 20%). When dining in groups, the split total is computed as (bill + tip) / n, where n is the number of diners, though tax is sometimes included before or after the split depending on local convention. Percentage and discount arithmetic is equally fundamental. A discount of 20% on a $45 item is computed as 45 × (1 − 0.20) = $36, and stacked discounts require sequential multiplication rather than addition of percentages. Fuel cost estimation uses the formula cost = (distance / mpg) × price per gallon, allowing drivers to budget road trips or compare vehicle efficiency. Electricity billing relies on unit conversion: kilowatt-hours equal watts × hours / 1000, and the cost is then kWh × the utility rate. A 100-watt bulb left on for 10 hours consumes one kWh, which at a rate of $0.13 amounts to 13 cents. Loan payment calculations typically apply the standard amortisation formula, where monthly payment depends on principal, interest rate per period, and number of periods. Understanding this formula helps consumers evaluate mortgage offers or auto loans without relying solely on lender summaries. Unit price comparison, dividing total price by quantity or weight, is the most direct tool for supermarket decisions and is often more revealing than advertised sale prices. Sales tax, typically a percentage added to a pretax subtotal, varies by jurisdiction and product category. Together, these calculations constitute a practical numeracy toolkit that reduces reliance on guesswork and supports more informed consumer behaviour across every domain of daily spending.
History
The history behind the Energy Use Intensity EUI Calculator traces back through the following developments. The history of everyday consumer arithmetic is inseparable from the broader story of commercial society and the gradual democratisation of mathematical tools. In pre-industrial economies, most transactions occurred in kind or relied on weights and measures governed by local custom rather than standardised formulas. The shift toward decimal currency, pioneered by the United States in 1792 and gradually adopted by European nations through the 19th and 20th centuries, made percentage calculations far more intuitive and accessible to ordinary citizens. The rise of the modern supermarket in the mid-20th century created a new demand for practical price comparison skills. Early consumer protection advocates in the 1960s and 1970s pushed for unit pricing legislation, recognising that larger packages were not always cheaper per ounce and that shoppers needed standardised information to compare products fairly. The US Fair Packaging and Labeling Act of 1966 was an early legislative response to these concerns. Personal finance software emerged in the early 1980s as home computers became affordable. Quicken, launched in 1983, was among the first widely adopted tools that automated bill tracking, loan amortisation, and budget projection for ordinary households. It shifted the culture from paper ledgers and mental arithmetic toward software-assisted financial management. The internet era brought free tools and comparison engines that extended these capabilities further. Mint, launched in 2006, aggregated bank and credit card data to provide automatic categorisation of spending, making budget tracking nearly effortless. Smartphone calculator apps, present on virtually every mobile device by 2010, placed instant arithmetic in every pocket. E-commerce platforms subsequently embedded tax calculators, shipping cost estimators, and instalment payment breakdowns directly into checkout flows, normalising real-time financial calculation as part of the purchasing experience. Today, the expectation that digital tools will perform these calculations instantly has become universal, yet understanding the underlying arithmetic remains valuable for interpreting results, catching errors, and making informed comparisons when automated tools are absent or misleading.
Frequently Asked Questions
Formula
EUI = Total Energy (kBtu) / Gross Floor Area (sq ft)
Where EUI is Energy Use Intensity in kBtu per square foot per year, Total Energy is the sum of all energy sources converted to kBtu (electricity kWh x 3.412 + gas therms x 100), and Gross Floor Area is the total building floor area in square feet.
Worked Examples
Example 1: Office Building EUI Calculation
Problem: A 25,000 sq ft office building consumed 300,000 kWh of electricity and 5,000 therms of natural gas in a year. Calculate the site EUI and compare to benchmark.
Solution: Electricity in kBtu: 300,000 kWh x 3.412 = 1,023,600 kBtu\nNatural gas in kBtu: 5,000 therms x 100 = 500,000 kBtu\nTotal energy: 1,023,600 + 500,000 = 1,523,600 kBtu\nSite EUI: 1,523,600 / 25,000 = 60.9 kBtu/sqft\nOffice benchmark: 78 kBtu/sqft\nPerformance: 60.9 / 78 = 78% of benchmark (Good)
Result: Site EUI: 60.9 kBtu/sqft | 22% better than the median office benchmark of 78 kBtu/sqft
Example 2: Hospital Source EUI Analysis
Problem: A 100,000 sq ft hospital uses 2,000,000 kWh of electricity and 40,000 therms of natural gas annually. Calculate site and source EUI.
Solution: Electricity site kBtu: 2,000,000 x 3.412 = 6,824,000 kBtu\nGas site kBtu: 40,000 x 100 = 4,000,000 kBtu\nTotal site kBtu: 10,824,000 kBtu\nSite EUI: 10,824,000 / 100,000 = 108.2 kBtu/sqft\nSource electricity: 6,824,000 x 2.80 = 19,107,200 kBtu\nSource gas: 4,000,000 x 1.05 = 4,200,000 kBtu\nSource EUI: 23,307,200 / 100,000 = 233.1 kBtu/sqft
Result: Site EUI: 108.2 kBtu/sqft | Source EUI: 233.1 kBtu/sqft | Below the hospital median of 250 (Good)
Frequently Asked Questions
What is Energy Use Intensity (EUI) and why does it matter?
Energy Use Intensity (EUI) is a metric that measures a building's energy consumption relative to its size, expressed in kBtu per square foot per year. It provides a standardized way to compare the energy performance of different buildings regardless of their size. EUI matters because it helps building owners, managers, and policymakers identify energy-efficient and energy-wasteful buildings. Lower EUI values indicate better energy performance, meaning the building uses less energy per square foot. This metric is central to energy benchmarking programs, green building certifications like LEED and ENERGY STAR, and many local building performance standards that cities are adopting.
What is the difference between site EUI and source EUI?
Site EUI measures the energy consumed at the building location, counting each unit of electricity and gas equally based on what the meter reads. Source EUI accounts for the total energy required to generate, transmit, and deliver that energy to the building. Electricity has significant transmission and generation losses, so its source multiplier is approximately 2.80, meaning for every 1 kBtu of electricity used on-site, about 2.80 kBtu of primary energy was consumed at the power plant. Natural gas has a much lower source multiplier of about 1.05 since it arrives relatively directly. Source EUI gives a more complete picture of total environmental impact and is the metric used by ENERGY STAR Portfolio Manager for benchmarking.
What are typical EUI values for different building types?
EUI values vary dramatically by building type due to different operational requirements. Warehouses are the most efficient at around 28 kBtu per square foot since they require minimal conditioning. Schools average about 58 kBtu per square foot, while multifamily residential buildings come in around 65 kBtu per square foot. Offices typically fall around 78 kBtu per square foot, and hotels average about 95 kBtu per square foot due to 24-hour operations. Hospitals are energy-intensive at approximately 250 kBtu per square foot because of specialized equipment and strict ventilation requirements. Restaurants top the list at roughly 432 kBtu per square foot due to heavy cooking equipment and ventilation needs.
How can I reduce my building EUI effectively?
Reducing building EUI requires a systematic approach starting with an energy audit to identify the largest energy consumers. Common strategies include upgrading HVAC systems to high-efficiency models, improving building envelope insulation and air sealing, installing LED lighting with occupancy sensors and daylight harvesting controls, and optimizing building automation system schedules. Retro-commissioning existing systems can often achieve 10-15 percent energy savings with minimal capital investment. Adding renewable energy sources like rooftop solar panels reduces site energy consumption directly. Behavioral changes and tenant engagement programs can also contribute 5-10 percent savings by encouraging energy-conscious habits like turning off equipment when not in use.
How do I convert between different energy units for EUI calculation?
To calculate EUI, all energy sources must be converted to a common unit, typically kBtu (thousand British Thermal Units). One kilowatt-hour of electricity equals 3.412 kBtu. One therm of natural gas equals 100 kBtu. One gallon of fuel oil equals approximately 139 kBtu. One cubic foot of natural gas equals approximately 1.036 kBtu. One gallon of propane equals approximately 91.5 kBtu. For metric conversions, one kBtu equals 1.055 megajoules. Once all energy sources are converted to kBtu, simply sum them and divide by the gross floor area in square feet to get the site EUI. Using consistent conversions is critical for accurate benchmarking.
What is ENERGY STAR Portfolio Manager and how does it relate to EUI?
ENERGY STAR Portfolio Manager is a free online tool provided by the EPA that allows building owners and managers to measure and track energy and water consumption, greenhouse gas emissions, and costs across their entire portfolio of buildings. It uses source EUI as the primary metric and compares your building against a national database of similar buildings to generate an ENERGY STAR score from 1 to 100, where 50 represents median performance. Buildings scoring 75 or higher are eligible for ENERGY STAR certification. Many cities now require annual benchmarking through Portfolio Manager as part of building performance disclosure ordinances. The tool accepts utility bill data and automatically handles unit conversions.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy