UK Government Conversion Factors 2026: SECR Calculations
Accurate carbon emissions reporting under the Streamlined Energy and Carbon Reporting (SECR) regulations requires using the correct conversion factors published annually by the UK Government. These factors translate your energy consumption data into greenhouse gas emissions measured in tonnes of carbon dioxide equivalent (CO2e).
This comprehensive guide explains the 2026 UK Government conversion factors, how to apply them correctly for SECR calculations, and how to ensure compliance with the GHG Protocol Corporate Standard.
Understanding UK Government Conversion Factors
The UK Government publishes Greenhouse Gas Conversion Factors annually to support consistent environmental reporting across UK businesses. These factors are based on the latest scientific data and align with international standards including the GHG Protocol.
Why Conversion Factors Matter
Conversion factors are the mathematical bridge between:
- Activity data: Energy consumed (e.g., 50,000 kWh of electricity)
- Emissions data: Carbon impact (e.g., 10.6 tonnes CO2e)
Using the correct, current-year factors is mandatory for SECR compliance and ensures your emissions reporting is:
- Accurate: Reflects latest grid carbon intensity and fuel compositions
- Comparable: Enables year-over-year tracking using consistent methodology
- Compliant: Meets Companies House SECR requirements
- Credible: Based on government-verified data sources
The 2026 Update
Each year, the UK Government updates conversion factors to reflect:
- Grid decarbonization: As renewable energy increases on the UK grid, electricity conversion factors decrease
- Fuel composition changes: Updates to average fuel carbon content
- Transportation updates: Changes in vehicle efficiency and fuel types
- Methodology improvements: Enhanced calculation approaches based on latest science
For financial years ending in 2026, you must use the 2026 conversion factors, not previous years' data.
Key 2026 Conversion Factors for SECR
Electricity Conversion Factors
UK electricity emissions vary by consumption type:
Grid Electricity (Location-Based Method):
- UK electricity: 0.21233 kgCO2e per kWh
- This represents the average carbon intensity of the UK grid in 2026
Transmission and Distribution Losses:
- T&D factor: 0.01698 kgCO2e per kWh
- Add this to account for energy lost in transmission
Total electricity factor: 0.21233 + 0.01698 = 0.22931 kgCO2e per kWh
Example Calculation:
- Annual consumption: 100,000 kWh
- Emissions: 100,000 × 0.22931 = 22,931 kgCO2e = 22.93 tonnes CO2e
Renewable Electricity: If you purchase electricity with Renewable Energy Guarantees of Origin (REGOs):
- REGO-backed electricity: 0 kgCO2e per kWh (market-based method)
- Reporting note: SECR allows market-based reporting but requires disclosure of methodology
Natural Gas Conversion Factors
Natural Gas (Gross CV basis):
- 100% natural gas: 0.18316 kgCO2e per kWh
This is the most common factor for UK businesses using mains gas for heating and hot water.
Example Calculation:
- Annual consumption: 200,000 kWh
- Emissions: 200,000 × 0.18316 = 36,632 kgCO2e = 36.63 tonnes CO2e
Important Note: Ensure your gas bills show consumption in kWh, not cubic meters. If billed in cubic meters, convert using the calorific value shown on your bill before applying conversion factors.
Transport Fuel Conversion Factors
Transport fuels require factors specific to fuel type and vehicle category.
Petrol (Average for company vehicles):
- Petrol (average): 2.31537 kgCO2e per litre
Diesel (Average for company vehicles):
- Diesel (average): 2.69869 kgCO2e per litre
LPG:
- LPG: 1.51427 kgCO2e per litre
Example Calculation (Company Car Fleet):
- Diesel consumed: 5,000 litres
- Emissions: 5,000 × 2.69869 = 13,493.45 kgCO2e = 13.49 tonnes CO2e
Biofuel Blends: Standard UK petrol contains up to 10% bioethanol (E10), and diesel contains up to 7% biodiesel. The factors above already account for these standard blends.
Grey Fleet Mileage Factors
For employee-owned vehicles used for business travel (grey fleet), conversion factors are expressed per distance traveled:
Average Car (Unknown Fuel Type):
- Average car: 0.17077 kgCO2e per mile
- Average car: 0.10611 kgCO2e per km
By Fuel Type:
- Petrol car (average): 0.15915 kgCO2e per mile
- Diesel car (average): 0.16619 kgCO2e per mile
- Hybrid car (average): 0.10804 kgCO2e per mile
- Electric car: 0.04736 kgCO2e per mile (includes upstream electricity generation)
By Vehicle Size (Petrol):
- Small petrol car: 0.13744 kgCO2e per mile
- Medium petrol car: 0.16186 kgCO2e per mile
- Large petrol car: 0.21227 kgCO2e per mile
Example Calculation (Grey Fleet):
- Business miles claimed: 25,000 miles
- Using average car factor: 25,000 × 0.17077 = 4,269.25 kgCO2e = 4.27 tonnes CO2e
Heating Fuels (Other Than Gas)
Heating Oil (Gas Oil / Red Diesel):
- Burning oil: 2.96139 kgCO2e per litre
LPG Bulk:
- LPG: 1.51427 kgCO2e per litre
Biomass:
- Wood chips: 0.01051 kgCO2e per kWh
- Wood pellets: 0.01397 kgCO2e per kWh
Coal:
- Coal (industrial): 0.32507 kgCO2e per kWh
Example Calculation (Heating Oil):
- Annual heating oil: 3,000 litres
- Emissions: 3,000 × 2.96139 = 8,884.17 kgCO2e = 8.88 tonnes CO2e
Understanding the GHG Protocol Scopes
SECR reporting follows the GHG Protocol Corporate Standard, which categorizes emissions into three scopes:
Scope 1: Direct Emissions
Emissions from sources you own or control:
Included in Scope 1:
- Natural gas combustion in your boilers
- Heating oil, LPG, or coal burned onsite
- Fuel in company-owned or leased vehicles
- Refrigerant leakage (if material)
- Process emissions from manufacturing
SECR Requirement: Mandatory reporting
Conversion Factors: Use fuel-specific factors (gas, diesel, petrol, heating oil) applied to your consumption data.
Scope 2: Indirect Energy Emissions
Emissions from purchased electricity, heat, or steam:
Included in Scope 2:
- Grid electricity consumed at all premises
- District heating or cooling
- Purchased steam
SECR Requirement: Mandatory reporting
Reporting Methods:
- Location-based: Use average grid factor (0.22931 kgCO2e/kWh including T&D)
- Market-based: Use supplier-specific factors or zero for REGO-backed renewable electricity
SECR allows either method but requires clear disclosure of your approach.
Conversion Factors: Use electricity factor (0.22931 kgCO2e/kWh) or district heating factors if applicable.
Scope 3: Other Indirect Emissions
Emissions from your value chain:
Commonly Included in SECR (Optional):
- Grey fleet business mileage
- Business air travel
- Hotel stays
- Taxi and rail travel
Not Typically Included in SECR:
- Employee commuting
- Supply chain (purchased goods and services)
- Waste disposal
- Downstream product use
SECR Requirement: Optional, but increasingly reported
Conversion Factors: Use distance-based factors for grey fleet (kgCO2e per mile or km).
Step-by-Step SECR Calculation Process
Step 1: Organize Your Energy Data
Collect 12 months of consumption data and organize by scope:
Scope 1 Data:
- Natural gas: 200,000 kWh
- Diesel (company vehicles): 5,000 litres
- Heating oil: 3,000 litres
Scope 2 Data:
- Grid electricity: 100,000 kWh
Scope 3 Data:
- Grey fleet: 25,000 miles
For data collection guidance, see our guide on SECR energy data collection.
Step 2: Apply Conversion Factors
Multiply each energy consumption figure by its corresponding 2026 conversion factor:
Scope 1 Calculations:
Natural gas: 200,000 kWh × 0.18316 = 36,632 kgCO2e
Diesel: 5,000 litres × 2.69869 = 13,493 kgCO2e
Heating oil: 3,000 litres × 2.96139 = 8,884 kgCO2e
Total Scope 1: 58,009 kgCO2e = 58.01 tonnes CO2e
Scope 2 Calculations:
Electricity: 100,000 kWh × 0.22931 = 22,931 kgCO2e
Total Scope 2: 22,931 kgCO2e = 22.93 tonnes CO2e
Scope 3 Calculations (Optional):
Grey fleet: 25,000 miles × 0.17077 = 4,269 kgCO2e
Total Scope 3: 4,269 kgCO2e = 4.27 tonnes CO2e
Step 3: Calculate Total Emissions
Mandatory SECR Total (Scope 1 + 2): 58.01 + 22.93 = 80.94 tonnes CO2e
Including Optional Scope 3: 80.94 + 4.27 = 85.21 tonnes CO2e
Step 4: Calculate Intensity Metric
SECR requires at least one intensity metric. Common options:
Emissions per Employee:
- Total emissions: 80.94 tonnes CO2e
- Employee count: 120
- Intensity: 80.94 ÷ 120 = 0.67 tonnes CO2e per employee
Emissions per £1M Turnover:
- Total emissions: 80.94 tonnes CO2e
- Annual turnover: £45 million
- Intensity: (80.94 ÷ 45) × 1 = 1.80 tonnes CO2e per £1M turnover
Emissions per Square Meter:
- Total emissions: 80.94 tonnes CO2e
- Total floor area: 5,000 m²
- Intensity: 80.94 ÷ 5,000 = 0.016 tonnes CO2e per m²
Advanced Conversion Factor Considerations
Well-to-Tank (WTT) vs Tank-to-Wheel (TTW)
The UK Government provides two types of emission factors:
Gross CV (Calorific Value) - Most Common for SECR: Includes combustion emissions only (tank-to-wheel or direct emissions)
WTT (Well-to-Tank): Includes upstream extraction, refining, and transmission emissions
For SECR compliance, use gross CV factors for Scope 1 and 2, as this aligns with GHG Protocol standards and avoids double-counting with Scope 3.
Location-Based vs Market-Based Electricity
Location-Based Method:
- Uses average UK grid factor (0.22931 kgCO2e/kWh including T&D)
- Simpler and more common for SECR
- Reflects actual grid carbon intensity
Market-Based Method:
- Uses supplier-specific factors or contractual instruments
- Allows reporting of zero emissions for REGO-backed renewable electricity
- Requires supplier emission factor disclosure
SECR Guidance: Either method is acceptable, but you must:
- State which method used in your methodology
- Be consistent year-over-year
- Provide both figures if claiming renewable electricity benefits
Transmission and Distribution Losses
When reporting electricity, you can choose to:
Exclude T&D: Use 0.21233 kgCO2e/kWh (grid generation only)
Include T&D (Recommended): Use 0.22931 kgCO2e/kWh (grid + transmission losses)
Including T&D provides a more complete picture of electricity-related emissions. Most SECR reporters include T&D for comprehensiveness.
Common Calculation Mistakes to Avoid
Mistake 1: Using Previous Years' Factors
Problem: Using 2025 or older conversion factors for 2026 reporting period
Impact: Inaccurate emissions calculations and potential non-compliance
Solution: Always use conversion factors matching your reporting year. Download the 2026 factors from gov.uk.
Mistake 2: Mixing Units
Problem: Applying kWh factors to litres or vice versa
Impact: Dramatically incorrect emissions figures (orders of magnitude errors)
Solution:
- Use litre-based factors for transport fuels (petrol, diesel)
- Use kWh-based factors for grid electricity and natural gas
- Convert gas bills from cubic meters to kWh before applying factors
Mistake 3: Forgetting T&D Losses
Problem: Using only the generation factor (0.21233) for electricity
Impact: Understating Scope 2 emissions by approximately 8%
Solution: Add T&D factor (0.01698) to generation factor, or use total factor (0.22931).
Mistake 4: Double-Counting Emissions
Problem: Including well-to-tank emissions in both Scope 1/2 and Scope 3
Impact: Overstating total emissions
Solution: Use gross CV factors for Scope 1 and 2, reserve WTT factors for specific Scope 3 upstream analyses.
Mistake 5: Incorrect Vehicle Factors
Problem: Using car factors for vans or vice versa
Impact: Inaccurate transport emissions
Solution: Match vehicle types to appropriate factors:
- Cars: Use car factors (0.17077 kgCO2e/mile average)
- Vans: Use van factors (0.25426 kgCO2e/mile average)
- HGVs: Use HGV factors by weight class
Conversion Factor Resources and Tools
Official UK Government Resources
Primary Source: 2026 Government GHG Conversion Factors for Company Reporting
Spreadsheet Tool: The government provides downloadable Excel spreadsheets with:
- All conversion factors organized by category
- Detailed methodology notes
- Previous years for comparison
Technical Guidance:
GHG Protocol Resources
Corporate Standard: GHG Protocol Corporate Accounting and Reporting Standard
Scope 2 Guidance: Scope 2 Guidance for Electricity Emissions
Calculation Tools: GHG Protocol provides free Excel-based calculation tools for various sectors.
Automated Calculation Tools
Manual application of conversion factors is time-consuming and error-prone. Modern platforms automate the entire process:
How Comply Carbon Handles Conversions:
- AI extracts consumption data from your utility bills
- System automatically identifies energy types (electricity, gas, diesel, etc.)
- Latest 2026 UK Government conversion factors applied automatically
- Emissions calculated by scope with full transparency
- Intensity metrics computed based on your business data
- Compliant SECR report generated with full methodology disclosure
This eliminates manual calculation errors and ensures you're always using current-year factors.
Year-Over-Year Comparison Considerations
Restating Previous Years
When conversion factors change significantly, you may consider restating previous years:
Arguments for Restating:
- Enables true like-for-like comparison
- Shows actual performance improvement vs. methodology changes
Arguments Against:
- SECR doesn't require restatement
- Maintains historical accuracy as reported
- Avoids confusion with previously published figures
Common Practice: Most SECR reporters do NOT restate previous years, instead noting in their methodology that year-over-year changes may reflect both performance and factor updates.
Tracking Actual Performance
To isolate actual energy reduction from conversion factor changes:
Track Energy Consumption: Report both energy (kWh) and emissions (tonnes CO2e) over time. Declining kWh consumption demonstrates real efficiency gains regardless of factor changes.
Normalize for Business Growth: Use intensity metrics to account for business expansion. Declining intensity shows improving efficiency even if absolute emissions increase.
Preparing for Future Factor Updates
2027 and Beyond
UK grid decarbonization means electricity conversion factors will continue declining:
- More renewable energy on the grid
- Coal-fired generation fully phased out
- Increased nuclear and offshore wind capacity
This trend means:
- Your electricity-related emissions will decrease even with constant consumption
- Focus efficiency efforts on Scope 1 (gas and fuel) where factors are more stable
- Consider electrification strategies (heat pumps, EVs) to benefit from grid decarbonization
Staying Current
Set reminders to:
- Download new conversion factors each June/July (typical release time)
- Update any internal calculation tools or spreadsheets
- Brief finance/sustainability teams on significant factor changes
- Consider implications for carbon reduction targets
Frequently Asked Questions
Q: Can I use Northern Ireland or Scotland-specific electricity factors? Yes, the UK Government provides country-specific factors. Use the factor matching where your electricity is consumed. However, most businesses use the UK average for simplicity.
Q: What if my electricity supplier provides their own emission factor? For market-based Scope 2 reporting, you can use supplier-specific factors if verified. Ensure the supplier follows recognized methodology and provides annual updates.
Q: How do I account for solar panels on my premises? Onsite renewable generation reduces your grid electricity consumption (Scope 2). Report net electricity purchased from grid. Some businesses voluntarily report renewable generation separately.
Q: Do I need to use different factors for different months? No, use the annual average factor for your entire reporting year. The UK Government factors already account for seasonal variations.
Q: What about carbon offsets or carbon credits? SECR reports gross emissions before any offsets. Carbon credits can be noted separately but don't reduce your reported SECR emissions.
Conclusion
Accurate application of UK Government conversion factors is essential for compliant SECR reporting. The 2026 factors reflect the latest grid decarbonization and fuel composition data, ensuring your carbon footprint accurately represents your business's environmental impact.
Key Takeaways:
- Always use conversion factors matching your reporting year (2026 for 2026 reports)
- Apply the correct factor type (kWh vs litres, cars vs vans)
- Include transmission and distribution losses for electricity
- Follow GHG Protocol scope classifications
- Document your methodology clearly
- Consider automation to eliminate calculation errors
For businesses seeking to streamline SECR compliance, Comply Carbon's automated platform applies the latest UK Government conversion factors automatically, eliminating manual calculation errors and ensuring 100% compliance with Companies House requirements.
Ready to simplify your SECR calculations? Get started with Comply Carbon or explore our complete SECR guide for comprehensive compliance support.