Building Energy Performance Calculator

Measure energy intensity, emissions, and benchmark alignment. Turn building data into practical performance decisions today.

Enter Building Performance Data

Example Data Table

Building Type Floor Area (m²) Electricity (kWh) Fuel (kWh) Renewables (kWh) Net EUI (kWh/m²·yr)
Office Block 1200 185000 95000 22000 215.00
School Wing 2400 248000 118000 45000 133.75
Retail Unit 800 99000 21000 7000 141.25

Formula Used

Gross Annual Energy = Annual Electricity + Annual Fuel Energy

Net Annual Energy = Gross Annual Energy − Onsite Renewable Generation

Energy Use Intensity = Net Annual Energy ÷ Floor Area

Conditioned EUI = Net Annual Energy ÷ Conditioned Area

Conditioned Area = Floor Area × Conditioned Area Ratio

Energy per Occupant = Net Annual Energy ÷ Occupants

Annual Operating Hours = Weekly Operating Hours × 52

Base Load Energy = Net Annual Energy × Base Load Ratio

Variable Load Energy = Net Annual Energy − Base Load Energy

Renewable Share (%) = Onsite Renewable Generation ÷ Gross Annual Energy × 100

Electricity CO₂ = Electricity Use × Electricity Emission Factor

Fuel CO₂ = Fuel Use × Fuel Emission Factor

Total CO₂ = Electricity CO₂ + Fuel CO₂

Carbon Intensity = Total CO₂ ÷ Floor Area

Performance Score (%) = Benchmark EUI ÷ Net EUI × 100

Benchmark Gap = Benchmark EUI − Net EUI

Climate Normalized EUI Index = (Net EUI × 1000 ÷ Climate Index) × 100

Climate Index = (Heating Degree Days × 0.55) + (Cooling Degree Days × 0.45)

How to Use This Calculator

Enter the building floor area and annual delivered energy values first. Add electricity, fuel, and onsite renewable generation in consistent yearly units.

Supply occupancy, operating hours, climate degree days, and benchmark EUI to expand the analysis. These fields help compare buildings more meaningfully.

Use emission factors that reflect your local grid and fuel conditions. This improves the carbon estimates and intensity indicators.

Click Calculate Performance to display the result summary above the form. Review the EUI, score, carbon intensity, and performance class.

Use the CSV button for spreadsheet analysis and the PDF button for reporting, meetings, or record keeping.

Frequently Asked Questions

1. What does EUI mean in this calculator?

EUI means energy use intensity. It shows annual net energy consumed per square meter of floor area, making building performance easier to compare.

2. Why is renewable generation subtracted?

Onsite renewable output offsets delivered energy demand. Subtracting it helps estimate net building energy performance after local generation contributes to operations.

3. Can I use this for offices and schools?

Yes. The calculator suits many building types, including offices, schools, retail spaces, and mixed-use facilities, as long as yearly inputs are consistent.

4. What is the benchmark EUI field for?

Benchmark EUI acts as a target or reference. The calculator compares your building against it and estimates a performance score and gap.

5. Are emission factors fixed values?

No. Emission factors vary by region, utility mix, and fuel source. Use local or project-specific values whenever available for better carbon estimates.

6. What does conditioned area ratio represent?

It estimates the portion of total floor area that is actively heated or cooled. This helps derive a conditioned EUI for focused analysis.

7. Why include heating and cooling degree days?

Degree days give climate context. They help create a normalization index so buildings in different weather conditions can be interpreted more fairly.

8. Does this calculator replace a formal energy audit?

No. It supports screening and benchmarking. Detailed audits still require end-use breakdowns, schedules, equipment data, and site-specific engineering review.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.