How to calculate your GHG emissions for VSME (without hiring a consultant)

Somewhere in your company there is a folder of invoices that contains your entire greenhouse gas footprint. Diesel for the vans. Gas for the boiler. The electricity bill. Maybe a service receipt for the air conditioning.

Turning that folder into the numbers your VSME report asks for is one multiplication, repeated:

activity data × emission factor = emissions

That’s it. That’s the method the official guidance describes, and the one every consultant uses. What you’re really paying a consultant for is knowing what counts as activity data, which factors to use, and where the traps are. This post covers those three things.

1) What VSME actually asks for

The energy and emissions disclosures sit in a few closely related sections of the VSME standard, and it pays to keep their codes straight:

• B3 is your total energy consumption in MWh, split into renewable and non-renewable if you can obtain that split.
• B3.2 is the emissions disclosure: your estimated gross Scope 1 emissions and location-based Scope 2 emissions, each in tonnes of CO₂ equivalent (tCO₂e). Market-based Scope 2 is optional on top.
• B3.3 is the intensity ratio: gross emissions divided by your turnover.
• Scope 3 is voluntary. If you choose to disclose it, it’s presented together with your B3.2 figures, and if you set reduction targets under the Comprehensive Module, the same gross figures become your C3.1 baseline.

One thing worth saying out loud: the standard’s own wording is “estimated gross GHG emissions”. Estimated. You are not expected to install meters on every exhaust pipe. You are expected to be transparent about your method and consistent from year to year.

2) The three scopes, translated for a normal company

Scope 1 is what you burn or leak. Fuel in company vehicles, gas in the boiler, LPG in the forklift, the generator behind the warehouse. It also includes refrigerant losses from air-conditioning and refrigeration. The convention there is simple: the kilograms your technician refilled during the year are treated as the kilograms that leaked, multiplied by that gas’s global warming potential. The refill amount is usually printed on the service invoice.

Scope 2 is energy made elsewhere that you buy. Electricity, district heating, purchased steam or cooling.

Scope 3 is everything else. Purchased goods, freight, business travel, commuting, waste, the use of the products you sell. The GHG Protocol splits it into fifteen categories, most of which won’t apply to you.

Two traps catch people every year:

• Electric vehicles burn nothing. Their charging is purchased electricity, so it belongs in Scope 2, not Scope 1. Counting an EV’s electricity under “fuels” is probably the most common first-draft mistake there is. (Plug-in hybrids are the exception: their petrol share still belongs in Scope 1.)
• Wood and biofuels are a special case. The CO₂ from burning biomass is reported as a separate memo item, outside your gross totals. (The methane and nitrous oxide from the same fire stay in Scope 1.)

3) The paperwork hunt

Before touching any calculator, collect one reporting year of:

• Fuel invoices or fuel-card statements: litres, per fuel type
• Gas bills: kWh or m³ (note which, the unit matters)
• Electricity bills: kWh, per country if you operate in several
• District heat or steam invoices: kWh or MWh
• AC and refrigeration service invoices: kilograms of refrigerant refilled, and the gas name (R-410A, R-32…)

If you have subsidiaries, gather this per entity. And decide your boundary once: the guidance describes the options, and operational control (you count everything you operationally run, leased vans included) is the sensible default for most SMEs. Whatever you pick, apply it everywhere and say so in the report.

A pleasant side effect: the same fuel and electricity entries give you the B3 energy figure in MWh almost for nothing. One folder of invoices, two disclosures.

4) The multiplication, and where the factors come from

An emission factor is just “kg of CO₂e per unit of activity”. Per litre of diesel (roughly 2.5 to 2.6 kg), per kWh of French versus Polish electricity (wildly different), per kilogram of R-410A leaked (over two tonnes; refrigerants are brutal).

You don’t have to invent these numbers, and you shouldn’t. The guidance lists public factor databases such as the IPCC’s Emission Factor Database and ADEME’s Base Empreinte. The sources Verdnt draws on are in the same family, all free and openly licensed: the UK Government’s annually updated conversion factors for company reporting, the European Environment Agency’s per-country electricity intensities, and IPCC AR6 global warming potentials for converting methane, nitrous oxide and refrigerants into CO₂e.

Grid factors are published a couple of years behind the reporting period. That’s normal for every tool and every consultant; you use the newest available and note it.

On location-based versus market-based Scope 2: location-based uses your country’s average grid mix and is what B3.2 requires. Market-based reflects your contracts (green power purchase agreements, certificates) and is worth adding as well, never instead, if you buy renewable electricity and want credit for it.

5) Four rules that keep your number defensible

1. Totals are gross. Offsets are never subtracted from Scope 1, 2 or 3. If you buy offsets, that’s a separate story you tell elsewhere.
2. Biogenic CO₂ stays outside the gross totals, as its own line.
3. One boundary, applied consistently.
4. Keep the trail. For each line: the quantity, the unit, the source document, and which factor (and factor edition) you multiplied by. When a bank’s analyst questions a figure, this trail is the answer. Next year, it’s your template.

That fourth rule is the real difference between a number and a defensible number.

6) So what does Verdnt’s GHG calculator actually do?

Exactly the process above, with the sharp edges filed off. You type what you know from the invoices (“14,200 litres of diesel”, “640,000 kWh of gas”, “12 kg of R-410A refilled”) and it applies the published factors: DESNZ conversion factors, EEA and JRC grid intensities, IPCC AR6 warming potentials. Scope 1, Scope 2 and Scope 3 each get their own tab, entries can be assigned to subsidiaries and consolidated, and the results panel shows tCO₂e per scope alongside the MWh figure for B3.

A few details worth knowing about:

• Every calculation carries a “How this was calculated” statement: a plain-language paragraph naming the standard, the factor sources and the boundary, with a copy button. Paste it straight into your report or your reply to the bank.
• Factors live in versioned packs (2026.3, for example), and a calculation stays pinned to its pack. A filed figure can be recomputed exactly, years later. Updating to newer factors is your explicit choice, never a silent change.
• The numbers don’t need retyping. Section B3.2 of your report has an Import from GHG calculator button that copies the figures straight in, into the current-year or base-year column, and records which calculation they came from.

The point isn’t magic. It’s that the multiplication, the factor bookkeeping and the audit trail, the tedious 90% of the job, shouldn’t cost you a consulting engagement.

Verdnt is free and launching soon. You can join the waitlist here.

Related reading: Is your site in a biodiversity-sensitive area? · What “high water stress” means in VSME · Choosing the Basic or Comprehensive module