Work Out Your Factory's Scope 1-2 Emissions in Excel

You have probably heard plenty of talk about "having to measure your carbon emissions". But when you actually try to start, it is daunting. "What is a Scope?" "Where do we get the data?" "How do we multiply the factors?" "Do we really have to hire consultants for this?" — these are the questions that come up most often from staff at the suppliers of large companies.

In this article we set out, step by step, a method of roughly calculating Scope 1 and Scope 2 that a non-specialist can follow.

What is a Scope — the three-drawer analogy

"Scope" is an international standard that divides carbon emissions into three drawers. The same emission is classified differently according to "who produced it directly". Using three desk drawers as an analogy, it works like this.

Why start with Scope 1 and 2

Of the three drawers, Scope 3 is the largest and most complex. It typically accounts for 70 to 90% of total emissions. But because Scope 3 requires data from across the whole supply chain, it is hard for a small or mid-sized manufacturer to touch it at the first step.

Scope 1 and 2, by contrast, need only data from inside our own company. City gas bills, KEPCO electricity bills, vehicle refuelling records, and purchase records for process fuels — with those four sets of material, a rough calculation is possible. That is why responding to RE100 and CBAM also starts, as standard, with Scope 1 and 2.

The calculation principle — there is only one formula

It looks complicated, but there is only one formula.

Suppose, for example, that our company used 10,000 N㎥ of city gas in a year. The emission factor for city gas is about 2.176 kg CO₂eq per N㎥ (on the basis of the national greenhouse gas inventory).

• 10,000 N㎥ × 2.176 = 21,760 kg CO₂eq = about 21.76 tCO₂eq

That is all. This is our company's Scope 1 emissions from a year of city gas. "How much did we use × how much carbon does it produce" — repeat that structure for each fuel and for electricity.

Emission factors by fuel and for electricity (for a rough calculation)

The fuel factors below are values in common use for rough calculations from the national greenhouse gas inventory, and the electricity factor is the 2023 power emission factor (consumption side) of 0.4173 tCO₂eq/MWh, confirmed by the National Greenhouse Gas Statistics Management Committee and published on 17 December 2025. Since 1 MWh is 1,000 kWh, that is the same as 0.4173 kg CO₂eq per kWh. Emission factors are updated, so before actually writing a report, please check the latest annual factors from the Ministry of Environment, the Korea Energy Agency, and the Greenhouse Gas Inventory and Research Center once more.

※ Source of the electricity factor: National Greenhouse Gas Statistics Management Committee, "2023 power emission factor" (consumption-side CO₂eq), 0.4173 tCO₂eq/MWh, published 17 December 2025. It is 8.1% lower than the preceding factor, the 2020–2022 average of 0.4541. The fuel factors are values in common use for rough calculations, cited from the national greenhouse gas inventory.

Calculating it step by step

Scope 2 is far simpler. You only need one number, your electricity consumption. For a factory using 500,000 kWh of electricity a year:

• 500,000 kWh × 0.4173 = 208,650 kg CO₂eq = about 208.65 tCO₂eq

How to read the number — is 230 tonnes a lot?

This is the part that most confuses people who have just done the calculation for the first time. Let us get a feel for it against a few benchmarks.

In the example factory, Scope 2 (emissions from electricity) accounts for the great majority of the total. For a company like this, renewable conversion is a very high priority.

Five things staff easily miss

1. Emission factors now change every year. Korea's power emission factor (consumption-side CO₂eq) fell 8.1%, from the 2020–2022 average of 0.4541 published in March 2025 to the 2023 factor of 0.4173 published on 17 December 2025. The more important change is the update cycle — from December 2025 the publication cycle was shortened from three years to one, so a new factor will come out every year from now on. Each factor has a different "target year" and "publication date", so use the factor for the correct year and always state the base year when you report. The CO₂ value KEPCO prints on your bill and in PowerPlanner reflects the national factor one cycle late, so it may differ from the value we calculate with the latest factor.

2. It is based on electricity used, not electricity purchased. If there is electricity you purchased but resold without using, calculate on the basis of net consumption.

3. Location-based vs market-based. There are two ways of calculating Scope 2. The location-based method uses the national average factor (the method used above); the market-based method uses the factor of the electricity actually purchased (reflecting green premium and REC purchases). To reflect your RE100 compliance record you have to use the market-based method, and in global reporting it is standard to state both values.

4. CBAM covers Scope 1 and 2 plus raw materials. CBAM reporting includes carbon emissions at the raw material stage as well as Scope 1 and 2. This part requires cooperation from suppliers, so it takes a long time.

5. Rough calculation vs precise calculation. What we did today is a rough calculation. Reporting to global buyers, official CBAM submissions, and ESG certification require a precise calculation (to ISO 14064 or the GHG Protocol). It is more efficient to grasp the scale first with a rough calculation and then refine it gradually to the level you need.

How to use the result

Once you have a carbon emissions figure, you can put it to three uses.

1. Setting a reduction target — it becomes possible to set a concrete target such as "currently 230 tCO₂eq → 115 tCO₂eq by 2030 (-50%)". Without a number there is no target either.
2. Designing a renewable energy portfolio — knowing how much of the total Scope 2 (emissions from electricity) accounts for lets you judge whether to prioritise RECs, a PPA, or self-generation.
3. Writing reports for customers — supplier assessment forms and ESG due diligence questionnaires from large companies include fields for Scope 1 and 2 emissions. A company that has prepared in advance is at a considerable advantage.

If you need a precise calculation

Once a rough calculation has shown you the scale, the next step is refinement. With 12 months of electricity bills and fuel consumption records to hand, market-based Scope 2 and Scope 1 by fuel can be organised from actual data, right through to values set out in the RE100 and CBAM reporting formats.