Breeam In Use Energy Calculator

Analyze building energy intensity, carbon emissions, and estimated performance rating for BREEAM In-Use Version 6 assessments.

What is the BREEAM In-Use Energy Calculator?

A BREEAM In-Use Energy Calculator is a specialized tool used by building managers, sustainability consultants, and property owners to quantify the energy efficiency of an existing asset. Unlike standard energy models, the BREEAM In-Use framework focuses on operational performance and asset capabilities. Using a BREEAM In-Use Energy Calculator allows stakeholders to identify how many credits they might earn under the Energy category (Part 2 and Part 3) of the assessment.

This tool is essential for anyone pursuing BREEAM certification. By inputting annual consumption data and floor areas, the calculator generates an Energy Use Intensity (EUI) metric, which is the cornerstone of sustainable building metrics. It helps demystify the complex point-scoring system of the Building Research Establishment (BRE), providing a clear pathway toward carbon neutrality.

A common misconception is that a BREEAM In-Use Energy Calculator only looks at electricity. In reality, it must account for all fuels, including natural gas, biomass, or district heating, to provide a holistic view of the building’s environmental impact.

BREEAM In-Use Energy Formula and Mathematical Explanation

The core of the BREEAM In-Use Energy Calculator relies on calculating the Energy Use Intensity (EUI) and comparing it against established benchmarks. The formula used in this calculator is:

EUI = (Annual Electricity + Annual Gas + Other Fuels) / Gross Internal Area (m²)

Once the EUI is determined, the calculator assesses the carbon footprint calculation using standard conversion factors (e.g., UK Government GHG Conversion Factors):

Total CO2e = (kWh Electricity * 0.233) + (kWh Gas * 0.183)

Variables Table

Variable	Meaning	Unit	Typical Range
Floor Area (GIA)	Total internal floor area of the building	m²	500 – 50,000
Electricity Usage	Annual consumption from utility bills	kWh/yr	Varies by asset type
Gas Usage	Heating or process fuel consumption	kWh/yr	0 – 500,000+
Benchmark Intensity	Target energy use for specific building types	kWh/m²	150 – 400

Practical Examples (Real-World Use Cases)

Example 1: Large City Office

A 5,000 m² office building in London uses 600,000 kWh of electricity and 200,000 kWh of gas per year. Using the BREEAM In-Use Energy Calculator:

• EUI: (600,000 + 200,000) / 5,000 = 160 kWh/m²/yr
• Benchmark (Office): 200 kWh/m²/yr
• Performance: 20% better than benchmark.
• Interpretation: The building likely qualifies for a “Very Good” or “Excellent” rating in the energy category, as it significantly outperforms standard office benchmarks.

Example 2: Retail Outlet

A 1,200 m² retail store uses 400,000 kWh of electricity (intensive lighting/HVAC) and no gas. Using the BREEAM In-Use Energy Calculator:

• EUI: 400,000 / 1,200 = 333 kWh/m²/yr
• Benchmark (Retail): 250 kWh/m²/yr
• Performance: 33% worse than benchmark.
• Interpretation: This asset requires urgent energy efficiency upgrades or an energy performance certificate review to achieve a “Pass” or “Good” BREEAM rating.

How to Use This BREEAM In-Use Energy Calculator

To get the most accurate results from our BREEAM In-Use Energy Calculator, follow these steps:

1. Gather Your Data: Collect 12 months of utility bills for all energy sources.
2. Input Floor Area: Enter the Gross Internal Area (GIA). Do not include external parking or balconies.
3. Select Asset Type: Choose the category that best matches your building to ensure the correct benchmark is applied.
4. Review the Primary Result: Look at the estimated rating. This provides a snapshot of where you stand today.
5. Analyze Intermediate Values: Pay attention to the EUI. This number is often used in ESG reporting and green building standards.
6. Adjust Scenarios: Use the calculator to see how a 10% reduction in electricity might change your overall BREEAM score.

Key Factors That Affect BREEAM In-Use Energy Results

Several financial and technical factors influence the outcomes of a BREEAM In-Use Energy Calculator:

• Occupancy Rates: High occupancy typically increases energy consumption but improves “per capita” metrics. However, BREEAM usually focuses on intensity per square meter.
• HVAC Efficiency: The age and maintenance of heating/cooling systems are the primary drivers of gas and electricity consumption.
• Local Grid Carbon Intensity: While the calculator uses standard factors, the actual carbon footprint of your energy depends on your specific utility provider’s fuel mix.
• Building Fabric: Insulation levels and glazing performance determine how much energy is “wasted” to maintain thermal comfort, directly impacting sustainable building metrics.
• Renewable Energy: On-site generation (like solar PV) can drastically reduce the “Electricity Usage” input, significantly boosting your BREEAM score.
• Operation Hours: 24/7 buildings will naturally have higher EUI compared to 9-to-5 offices, which is why choosing the correct benchmark is vital for fair comparison.

Frequently Asked Questions (FAQ)

1. What version of BREEAM does this calculator support?

This BREEAM In-Use Energy Calculator is designed based on the logic used in Version 6, focusing on Asset Performance and EUI metrics.

2. Is EUI the only thing that matters for the Energy rating?

No. While EUI is critical, BREEAM also looks at energy monitoring, management practices, and lighting controls. However, EUI is the largest contributor to the quantitative score.

3. How does gas usage impact my CO2 results differently than electricity?

In most regions, electricity has a higher carbon intensity per kWh than natural gas. Reducing 1 kWh of electricity usually has a greater positive impact on your carbon footprint calculation than reducing 1 kWh of gas.

4. Can I use this for a residential building?

BREEAM In-Use is primarily for commercial/institutional assets. While you can input residential data, the benchmarks used in this BREEAM In-Use Energy Calculator are commercial-focused.

5. Does this calculator provide an official BREEAM certificate?

No. This tool provides an estimate. To get an official rating, you must engage a licensed BREEAM Assessor and submit evidence to the BRE.

6. Why is floor area so important?

The EUI calculation is highly sensitive to the denominator (m²). An incorrect floor area will lead to an inaccurate performance assessment and incorrect credits.

7. How often should I recalculate my building’s energy performance?

BREEAM In-Use certificates are typically valid for three years, but you should use the BREEAM In-Use Energy Calculator annually to track improvements.

8. What is the difference between Part 2 and Part 6?

Part 2 measures Asset Performance (the building itself), while Part 6 (now often integrated into Part 3) measures management performance. Our calculator focuses on the physical asset’s efficiency.

Related Tools and Internal Resources

• BREEAM Certification Guide – A comprehensive roadmap to achieving high scores in BREEAM assessments.
• Sustainable Building Metrics Explained – Understanding the KPIs that drive modern real estate sustainability.
• Energy Performance Certificate Basics – How EPCs differ from BREEAM ratings and why both matter.
• Carbon Footprint Calculation Tips – Best practices for reporting Scope 1 and Scope 2 emissions.
• Green Building Standards Overview – Comparing BREEAM, LEED, and DGNB for international portfolios.
• Commercial Energy Audit Checklist – How to prepare for your next on-site energy assessment.