How to calculate your small business's carbon footprint from your bills
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Your carbon footprint sounds complicated, but for most small businesses the first version is just three numbers from your bills multiplied by three conversion factors.
This guide shows you which bills to find, how the maths works, and how to turn the result into something you can share with customers.
The short version
- You need 12 months of electricity, gas (or other heating fuel) and vehicle fuel data.
- Multiply each by a conversion factor to get kilograms of CO₂e (carbon dioxide equivalent), then add them up.
- Save the result each year so you can show it going down.
Step 1: Gather 12 months of data
| What | Unit | Where to find it |
|---|---|---|
| Electricity | kWh | Electricity bills or your supplier's online account |
| Gas or other heating fuel | kWh (or litres for oil/LPG) | Gas bills or fuel delivery invoices |
| Company vehicle fuel | Litres (or miles) | Fuel cards, receipts or mileage claims for company vehicles |
Step 2: Multiply by conversion factors
A conversion factor tells you how many kilograms of CO₂e come from one unit of energy or fuel. In the UK, the government publishes official factors every year (the DESNZ greenhouse gas conversion factors). Granular's estimator uses indicative factors in line with them:
| Source | Scope | Factor |
|---|---|---|
| UK grid electricity | Scope 2 | 0.207 kg CO₂e per kWh |
| Natural gas | Scope 1 | 0.183 kg CO₂e per kWh |
| Diesel | Scope 1 | 2.51 kg CO₂e per litre |
| Petrol | Scope 1 | 2.08 kg CO₂e per litre |
Not sure what Scope 1 and 2 mean? See Scope 1, 2 and 3 explained.
A worked example
A small workshop uses, over a year:
| Source | Use | Calculation | Emissions |
|---|---|---|---|
| Electricity (Scope 2) | 20,000 kWh | 20,000 × 0.207 | 4.14 tonnes |
| Gas heating (Scope 1) | 30,000 kWh | 30,000 × 0.183 | 5.49 tonnes |
| Van diesel (Scope 1) | 2,000 litres | 2,000 × 2.51 | 5.02 tonnes |
| Total | 14.65 tonnes CO₂e |
So this business's Scope 1 & 2 footprint is about 14.65 tonnes of CO₂e a year, and over two-thirds of it comes from gas and diesel. That tells them where to focus: heating controls and vehicle choices before anything else.
Frequently asked questions
How do I calculate my carbon footprint as a small business?
Collect 12 months of electricity, gas and vehicle fuel use, multiply each by an emissions conversion factor (kg CO₂e per kWh or per litre), and add them up. That gives your Scope 1 and 2 footprint.
Where do UK carbon conversion factors come from?
The UK government (DESNZ) publishes greenhouse gas conversion factors for company reporting every year. Use the latest set for formal reporting.
What if I work from home or share an office?
Use your share of the building's energy if your landlord can provide it, or estimate based on floor area. Home-working emissions can be counted later as part of Scope 3.
Found this useful? Pass it on to someone who's been asked the same question.
Official sources
- GHG Protocol — Corporate Standard (opens in a new tab)
- GOV.UK — Environmental reporting guidelines (opens in a new tab)
This guide is educational and not legal advice. Thresholds are simplified and rules change, so always confirm with the official source or an adviser.
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