A customer questionnaire asks for your greenhouse gas emissions. It may say Scope 1 and 2, or Scope 3, or carbon footprint in tCO2e. This guide explains what the terms mean, what a supplier is actually expected to report, and how to produce the figure from records you already have.
| First question | Short answer |
|---|---|
| What do I have to report? | Scope 1 and Scope 2, in metric tons CO2e, for the year the customer specifies. Scope 3 is asked for less often and is not expected from most SMEs. |
| Why does the customer want it? | Your emissions are their Scope 3. They cannot report theirs without yours. |
| What data do I need? | Twelve months of electricity, gas, and fuel consumption, plus refrigerant top-ups if any. |
| Do I need verification? | Not for a first response. Self-calculated figures with documented methodology are accepted. |
| How long does it take? | The first calculation is the slow one because of data gathering. Annual updates are routine once the data is tracked. |
The three scopes, plainly
The GHG Protocol — the carbon accounting standard almost every questionnaire references — divides a company's emissions into three scopes. The split assigns responsibility and stops the same metric ton of CO2 being counted twice as it moves through a supply chain.
Scope 1: what you burn or leak
Emissions from sources you own or control. For a typical 50-person manufacturer:
- Company vehicles — delivery vans, service trucks, company cars on diesel or petrol
- On-site fuel — natural gas heating the building, propane in forklifts, diesel in a generator
- Process emissions — if the manufacturing chemistry itself releases gases (cement, some chemical processes); most SMEs have none
- Refrigerant leaks — top-ups to air conditioning or cold storage, recorded on the service invoice; small quantities, but the gases are hundreds to thousands of times more potent than CO2
If you rent an office with electric heating and have no vehicles, Scope 1 can be zero. That is a legitimate answer.
Scope 2: the energy you buy
Emissions from purchased electricity, steam, heating, or cooling. The power station created them; you consumed the energy, so you report them. The same emissions are the utility's Scope 1. They enter the atmosphere once and responsibility is shared along the chain. For most small businesses Scope 2 is larger than Scope 1. For an office-based company it is nearly the entire footprint.
Scope 3: everything else in your value chain
All other indirect emissions, upstream and downstream. The GHG Protocol lists 15 categories. The ones that usually matter for an SME: purchased goods and services (materials and components — normally the largest for a manufacturer), upstream transport, business travel, employee commuting, waste, and, for some products, the energy the product uses in the customer's hands. For a service company, travel and commuting typically dominate.
Why your customer needs your figure
Your Scope 1 and 2 (and your Scope 3, if you report it) are what your customer records as their Scope 3, Category 1: Purchased Goods and Services. For most large companies Scope 3 is the majority of their footprint, and they cannot calculate it without supplier data. That is why the questionnaire arrived.
Regulation drives the request. The EU Corporate Sustainability Reporting Directive and frameworks such as CDP require Scope 3 reporting from large companies. If you sell steel, aluminum, cement, or fertilizers into the EU, there is a second driver: the EU carbon border mechanism (CBAM) requires importers to report the embedded emissions of what they buy, which they can only get from you.
What to report
At minimum, Scope 1 and Scope 2. Some customers ask for Scope 3 as well; for most small and mid-sized suppliers, Scope 1 plus 2 is the expectation.
Report annual emissions in metric tons of CO2 equivalent (tCO2e) for the calendar or fiscal year the customer specifies. They may ask for absolute emissions, an intensity figure (tCO2e per unit of revenue or production), or both.
Scope 1 sources: natural gas in boilers or heaters; diesel or petrol in company vehicles; refrigerant leaks; on-site processes if applicable.
Scope 2 sources: purchased electricity; purchased steam or district heating (less common for small suppliers).
Collecting activity data
A GHG calculation needs activity data (how much energy you used) and emission factors (how much CO2e each unit produces).
Electricity. Annual consumption in kWh from utility bills. Sum twelve months or request an annual statement. The free Scope 2 calculator converts the annual kWh into emissions.
Natural gas. Bills show therms, cubic meters, or kWh. Note the unit; factors differ by unit.
Vehicle fuel. Fuel card statements or purchase records show liters or gallons by fuel type. Mileage and average consumption is an acceptable fallback; direct fuel data is more accurate.
Refrigerants. If HVAC servicing included a top-up, the service record shows the type and quantity added. That goes into Scope 1.
Organize the data by source and by site if you have several. Customers with multi-country supply chains usually want a site-level breakdown.
Finding emission factors
Use published factors from a recognized source, for the same year as the activity data or the most recent available.
Electricity (Scope 2): national government publications (DEFRA in the UK, EPA eGRID in the US, and equivalents); International Energy Agency country factors; your electricity supplier's published factor.
Fuels (Scope 1): DEFRA conversion factors (UK, widely used internationally); EPA factors (US); IPCC defaults where no national data exists.
Refrigerants (Scope 1): IPCC global warming potential values; EPA reference tables.
Sample calculation
A small manufacturing site consumed in one year:
- Electricity: 120,000 kWh
- Natural gas: 15,000 kWh
- Diesel (vehicles): 3,000 liters
Scope 2 (electricity): 120,000 kWh × 0.233 kgCO2e/kWh (example grid factor) = 27,960 kgCO2e = 27.96 tCO2e
Scope 1 (natural gas): 15,000 kWh × 0.184 kgCO2e/kWh = 2,760 kgCO2e = 2.76 tCO2e
Scope 1 (diesel): 3,000 liters × 2.687 kgCO2e/liter = 8,061 kgCO2e = 8.06 tCO2e
Total Scope 1: 10.82 tCO2e. Total Scope 2: 27.96 tCO2e. Scope 1 + 2: 38.78 tCO2e.
With annual revenue of $5 million, emission intensity is 7.76 tCO2e per $1 million revenue.
The factors above are illustrative. To run the calculation with current factors and your own figures, the free carbon calculator applies them to your electricity, gas, and fuel data.
Reporting formats
Direct questionnaires. Custom spreadsheets or online forms asking for Scope 1, Scope 2, a breakdown by source, and sometimes methodology.
CDP Supply Chain. The customer invites you to disclose through CDP, which has a structured emissions section. See the CDP supply chain guide.
EcoVadis. Asks for emissions in the Environment theme, with evidence of the calculation.
Product-level requests. Some customers want emissions per unit of product rather than a company total. This requires allocating site emissions across products; the product carbon footprint guide covers it.
The underlying data is the same in every format. ESG Passport stores the emissions data once and drafts it into each questionnaire's structure.
Documenting the methodology
Customers increasingly ask how you calculated the figure. Record:
- Data sources (bills, fuel records, meter readings)
- Emission factors used (source, year, region)
- Method (GHG Protocol Scope 1 and 2 guidance)
- Organizational boundary (which sites)
- Reporting period
A one-paragraph methodology note is enough. It answers the auditor's questions before they are asked.
When third-party verification matters
For most small suppliers responding to a first request, self-calculated emissions are accepted. Verification becomes relevant when:
- The customer requires it (uncommon for small-spend suppliers)
- You make public climate claims or commitments
- You join a program that requires verified data (SBTi and some industry schemes)
Verification is a paid engagement with an accredited assurer. Cost scales with the number of sites and the assurance level. Get a quote before assuming it is needed.
Scope 3 for suppliers
Some customers ask suppliers to report their own Scope 3. For a small supplier this means obtaining emissions data from your own suppliers, which most cannot yet do. If asked, say what you can estimate (business travel, waste, a screening of purchased goods) and what you cannot. Customers understand that Scope 3 cascades down supply chains over years. Accurate Scope 1 and 2 is the priority.
Making the data useful
Once you have a baseline, the value is in the pattern. High Scope 1 points at fuel efficiency, fleet electrification, or replacing gas heating. High Scope 2 points at energy efficiency or renewable electricity procurement. High Scope 3, if you estimate it, points at supplier choice and material substitution. Companies measuring for the first time routinely find the generator that runs more than anyone realized, or the site using twice the energy per square meter of the others. Neither shows up until the numbers do.
If a customer asks for the emissions of a specific product rather than the company, that is a different calculation: the product carbon footprint guide explains how those requests work.
Building the capability
The first calculation takes longest: finding data sources, choosing factors, documenting the method. After that, annual updates are routine if the same data points are logged monthly or quarterly. Suppliers with the tracking in place respond to the next request from records rather than from a search. The figure you report is also a baseline for reduction, and increasingly a condition of preferred-supplier status with customers that have their own climate targets.