Carbon Emission Factors – How to Choose the Right Data for Carbon Footprint Calculations

1,000 MWh of energy consumption is still 1,000 MWh of energy. Yet the resulting carbon footprint may differ depending on the emission factor applied.

This is why selecting an emission factor is not merely a technical detail of the calculation. It is one of the factors that determines the reliability of the final result.

In practice, organisations use a wide range of data sources: national KOBiZE emission factors, electricity and heat supplier data, UK Government conversion factors commonly referred to as DEFRA factors, LCA databases such as ecoinvent, EXIOBASE, IPCC data and information obtained directly from suppliers.

The challenge is not simply finding an emission factor.

The key question is:

Which emission factor is appropriate for the specific activity, location, reporting period and purpose of the calculation?

At its most basic level, an emissions calculation follows a simple relationship:

activity data × emission factor = greenhouse gas emissions

Activity data may include litres of fuel consumed, kWh of electricity, kilometres travelled, tonnes of materials purchased, quantities of waste generated or the monetary value of purchased goods and services.

As the number of emission sources and organisational units increases, it becomes increasingly important to manage not only the activity data themselves, but also the information about the emission factors used.

TABLE OF CONTENTS

1. What is an emission factor?
2. Why can the choice of emission factor change your carbon footprint result?
3. KOBiZE – when should Polish national emission factors be used?
4. Electricity and heat supplier data
5. DEFRA – emission factors for a wide range of activities
6. ecoinvent – data for LCA and Product Carbon Footprint
7. EXIOBASE – when detailed physical data are not available
8. IPCC – a key source of emissions methodologies and factors
9. How to choose the right emission factor
10. The most common mistakes when selecting emission factors
11. Why the source of an emission factor should be documented
12. How NEOGAGE Carbon Footprint supports emission factor management
13. Checklist before applying an emission factor
14. Conclusion
15. FAQ

What is an emission factor?

An emission factor represents the amount of greenhouse gas emissions associated with a specific unit of activity.

It may, for example, be expressed as:

• kg CO₂e/kWh of electricity, • kg CO₂e/litre of fuel, • kg CO₂e/tonne-kilometre of transport, • kg CO₂e/kg of material, • kg CO₂e/kg of waste, • kg CO₂e/unit of expenditure.

At first glance, the calculation appears straightforward.

An organisation takes a certain amount of energy, fuel or material consumption, multiplies it by the relevant factor and obtains an emissions result.

However, one of the most significant risks arises before the calculation even begins – when the emission factor itself is selected.

An emission factor may vary depending on:

• country, • reporting year, • technology, • fuel type, • energy source, • supplier, • system boundaries, • unit, • whether the calculation concerns an organisational or product carbon footprint.

This means that two factors both described as “electricity emission factors” may not represent exactly the same thing.

H2: Why can the choice of emission factor change your carbon footprint result?

Electricity provides a useful example.

A different result may be obtained when using an average grid emission factor compared with a calculation based on information relating to a specific energy procurement arrangement, where the chosen methodology allows this.

For Scope 2 emissions, the GHG Protocol distinguishes between the location-based and market-based methods.

The location-based method reflects the average emissions intensity of the electricity grid within a defined geographical area.

The market-based method reflects emissions associated with the electricity a company has chosen to purchase, based on qualifying contractual instruments where the relevant criteria are met.

This means that asking:

“What is the emission factor for electricity?”

is often too broad a question.

A more useful question is:

Which factor is appropriate for this reporting period, country, emissions scope and accounting method?

KOBiZE – when should Polish national emission factors be used?

KOBiZE is one of the key Polish sources of data used in greenhouse gas emissions calculations.

Its published indicators and emission factors can be used, among other applications, in calculations relating to electricity and other emission sources relevant to Polish conditions.

However, this does not mean that any value found online and labelled as a “KOBiZE emission factor” can automatically be used in a carbon footprint calculation.

Before applying a factor, you should verify:

• the year to which the data relate, • the unit in which the factor is expressed, • what the factor specifically represents, • which boundaries it covers, • the purpose for which it was developed.

It is particularly important to retain information about the source and version of the factor used.

If the carbon footprint calculation is repeated in a subsequent year, the organisation should be able to determine not only the previous result, but also which data and emission factors were used to produce it.

Electricity and heat supplier data

In some cases, it may be possible to use electricity or heat emission data published by a specific supplier.

Such information may allow an organisation to apply an emission factor that more closely reflects the actual energy procurement arrangement.

However, it should not be assumed that every supplier-specific factor automatically replaces a national average.

The appropriate choice depends on the accounting methodology and the scope of the calculation.

When supplier-specific data are used, it is good practice to retain:

• the source name, • the emission factor value, • the unit, • the period for which it applies, • the document from which it originates, • information about the accounting method in which it was used.

In NEOGAGE Carbon Footprint 2.8.0, the available resources were expanded to include new emission factor databases for electricity and heat suppliers in Poland for 2025.

DEFRA – emission factors for a wide range of activities

The term DEFRA factors is commonly used to refer to UK Government greenhouse gas conversion factors.

The database covers a broad range of activities, including:

• fuels, • energy, • transport, • business travel, • freight transport, • waste, • water.

The factors are regularly updated.

NEOGAGE Carbon Footprint 2.8.0 also includes the DEFRA 2026 database.

DEFRA is a valuable source of emissions data, but this does not mean that every UK emission factor should automatically be applied to activities taking place in Poland or other countries.

The type of activity, geographical context and methodological compatibility of the factor should always be considered.

Good carbon accounting practice is therefore not about selecting one preferred database for the entire organisation.

Each factor should be appropriate for the specific emission source being calculated.

ecoinvent – data for LCA and Product Carbon Footprint

ecoinvent serves a different purpose from a basic table of fuel or electricity emission factors.

It is a comprehensive life cycle inventory database widely used in Life Cycle Assessment – LCA.

It contains data covering a wide range of processes, including:

• material production, • energy, • transport, • fuels, • metals, • chemicals, • agriculture, • waste management, • industrial processes.

ecoinvent is particularly relevant to Product Carbon Footprint calculations.

When an organisation wants to determine the carbon footprint of a specific product, knowing how much electricity was consumed at the manufacturing site is often not sufficient.

The calculation may also need to include emissions associated with raw materials, components, transport and other life-cycle stages that fall within the defined system boundaries.

For this reason, ecoinvent datasets should not be treated as a simple substitute for every national emission factor.

They serve a different purpose and often provide a different level of detail.

EXIOBASE – when detailed physical data are not available

EXIOBASE is a multi-regional environmentally extended input-output database linking economic information with environmental data.

It can be particularly useful for:

• Scope 3 analysis, • value-chain screening, • spend-based emissions estimates, • preliminary calculations where detailed supplier data are not yet available.

For example, an organisation may know how much it has spent on a category of services but may not have information about the supplier’s actual energy, fuel or material consumption.

In such a situation, environmentally extended economic data may provide a basis for an initial emissions estimate.

However, a spend-based result should not be treated as equivalent to a detailed calculation based on physical activity data.

As data quality improves, organisations can move from sector-average and spend-based factors towards more specific physical data or supplier-specific information.

IPCC – a key source of emissions methodologies and factors

IPCC Guidelines underpin many of the methods used to calculate greenhouse gas emissions.

They cover areas such as fuel combustion, industrial processes and other emissions sources.

However, this does not mean that a generic IPCC factor will always be the best option.

Where a reliable and more specific factor is available for a particular technology, fuel, location or source, it may provide a more representative estimate of actual emissions.

The principle is straightforward:

the better an emission factor represents the actual activity being assessed, the more likely it is to produce a representative result.

How to choose the right emission factor

There is no single database that is appropriate for every type of emission.

Emission factor selection should begin with several basic questions.

1. What exactly are you calculating?

Is the calculation intended for:

• an organisational carbon footprint, • Scope 1, • Scope 2, • Scope 3, • Product Carbon Footprint, • an LCA study?

The purpose of the calculation affects the type of data required.

2. What activity data are available?

Do you know:

• litres of fuel consumed, • kWh of electricity, • transport distance, • tonnes of materials, • quantities of waste, • supplier-specific activity data,

or only:

• monetary expenditure?

The more specific the activity data, the greater the opportunity to use an emission factor that reflects the actual process.

3. Where does the emission-generating activity take place?

Geography can significantly affect the appropriate factor.

This is particularly relevant to electricity and heat, where emissions intensity can vary substantially between countries, regions and suppliers.

4. Which reporting year does the activity relate to?

Emission factor databases are updated over time.

Electricity mixes change. Technologies evolve. Fuel characteristics and statistical datasets are revised.

For this reason, the database version used should be selected deliberately for the reporting period concerned.

5. What boundaries does the emission factor cover?

This is one of the most frequently overlooked questions.

Two factors may apply to the same unit of activity but cover different parts of the life cycle.

For example, emissions from the direct combustion of a fuel are not the same as life-cycle emissions associated with extracting, processing, transporting and ultimately using that fuel.

The most common mistakes when selecting emission factors

Mistake 1. Using the first emission factor found online

A numeric value alone is not enough.

Its source, year, unit and methodological scope must also be known.

Mistake 2. Mixing emission factors from different years without methodological control

If an organisation changes data sources between reporting periods without documenting the methodology, year-on-year comparisons may become distorted.

Mistake 3. Ignoring geography

A factor appropriate for one country may not accurately represent an activity carried out in another.

Mistake 4. Using inconsistent units

kg CO₂e/kWh, kg CO₂e/MWh, kg CO₂e/litre and kg CO₂e/kg of product cannot be used interchangeably without correct unit conversion.

Mistake 5. Failing to distinguish between Scope 1, Scope 2 and Scope 3

A similar activity may require a different approach depending on which part of the carbon footprint is being calculated.

Mistake 6. Using a highly generic factor when better data are available

Sector-average factors can be useful when more specific information is unavailable.

However, where reliable process-specific or supplier-specific data are available, it is worth assessing whether they provide a better representation of the activity.

Mistake 7. Failing to record the source of the emission factor

A year later, the result may still exist in a spreadsheet, but nobody remembers:

• where the factor came from, • which year it represented, • why it was selected, • whether a more recent version was subsequently published.

This makes the calculation much more difficult to reproduce or verify.

Why the source of an emission factor should be documented

A credible carbon footprint is more than a final number expressed in tonnes of CO₂e.

The calculation process should be reproducible.

For important emission factors, it is therefore advisable to retain:

• the factor name, • its numerical value, • unit, • source, • database year or version, • validity period, • emissions category, • information about how and where it was applied.

This becomes particularly important during subsequent reporting periods, external verification and trend analysis.

If a result changes significantly from one year to the next, the organisation should be able to determine whether the change was caused by:

• an actual reduction in emissions, • a change in business activity, • improved source data, • or an updated emission factor.

How NEOGAGE Carbon Footprint supports emission factor management

With only a small number of emission sources, emission factors may still be managed in a spreadsheet.

However, as the number of sites, emission categories, products and reporting periods increases, so does the risk of:

• different users applying different sources, • outdated emission factors being used, • incorrect unit conversions, • source information being lost, • previous calculations becoming difficult to reproduce.

NEOGAGE Carbon Footprint helps organisations manage this process within one structured environment.

The system supports databases and data sources including:

• ecoinvent, • EXIOBASE, • DEFRA, • IPCC, • KOBiZE, • URE, • electricity supplier emission factors, • district heating supplier emission factors.

Users can also define their own emission factors.

The system supports assigning factors to calculations, using default emission factors and retaining information about the data used during the calculation process.

NEOGAGE Carbon Footprint 2.8.0 additionally introduces:

• new 2025 emission factor databases for electricity suppliers in Poland, • updated heat supplier data, • the DEFRA 2026 database.

The value of such a system is not that the software replaces methodological judgement.

Its role is to organise data, reduce the risk of accidentally applying an incorrect or outdated value and maintain a consistent calculation history.

Checklist before applying an emission factor

Before using an emission factor, verify:

1. Does it come from a credible source?
2. Does it correspond to the correct type of activity?
3. Is it appropriate for the relevant geography?
4. Does the database version or year correspond to the reporting period?
5. Is the unit consistent with the activity data?
6. Do you understand which emissions boundaries the factor covers?
7. Will the source and version be recorded together with the calculation?

If the answer to any of these questions is “I don’t know”, the factor should be reviewed before it is used in the final calculation.

Conclusion

KOBiZE, DEFRA, ecoinvent, EXIOBASE and IPCC are not competing to be the single “best” emission factor database.

They serve different purposes, provide different levels of detail and cover different types of data.

Professional carbon accounting is therefore not about finding one number and applying it across the entire organisation.

It is about matching the emission factor to:

the emission source, activity data, geography, reporting period and calculation boundaries.

As the scale of carbon accounting grows, it also becomes increasingly important to be able to answer three simple questions:

Which emission factor was used?

Where did it come from?

Why was it selected?

NEOGAGE Carbon Footprint helps organisations structure this process – from activity data and emission factor management through calculations, analysis and reporting.

FAQ – carbon emission factors and carbon footprint calculations

What is a carbon emission factor?

An emission factor is a coefficient used to convert a specific activity – such as fuel consumption, electricity consumption or material use – into the corresponding quantity of greenhouse gas emissions.

Is there one universal emission factor for electricity?

No. The appropriate factor may depend on the country, reporting year, source of the data and whether a location-based or market-based Scope 2 approach is being used.

Can the same emission factor be used for several years?

This should not be assumed automatically. Many emission factor databases are updated regularly, so the version and relevance of the factor should be reviewed for each reporting period.

What is the difference between KOBiZE and DEFRA?

KOBiZE provides data relevant to Polish conditions and national emissions accounting. DEFRA commonly refers to UK Government conversion factors covering a wide range of activities. The two sources should not be treated as automatically interchangeable.

When should ecoinvent be used?

ecoinvent is particularly useful in Life Cycle Assessment and Product Carbon Footprint calculations where data are required for materials, processes, energy, transport and other life-cycle stages.

What is EXIOBASE used for?

EXIOBASE supports environmentally extended economic analysis and spend-based emissions calculations. It can be particularly useful for initial Scope 3 screening when detailed physical activity data are not yet available.

Are supplier-specific data always better than average emission factors?

Not necessarily. Supplier-specific data must be reliable, complete and methodologically appropriate. Where high-quality source-specific data are available, however, they may provide a more representative result than a highly generic average factor.

Why does the year of the emission factor matter?

Because electricity mixes, technologies, fuel characteristics and statistical datasets change over time. Using a factor from a different period may affect the result and reduce comparability between reporting years.

Which emission factor databases are supported by NEOGAGE Carbon Footprint?

NEOGAGE Carbon Footprint supports work with sources including ecoinvent, EXIOBASE, DEFRA, IPCC, KOBiZE, URE and emission factors published by electricity and heat suppliers. The system also allows users to define their own emission factors.

Does NEOGAGE automatically decide which emission factor is methodologically correct?

NEOGAGE should not be treated as a substitute for expert methodological judgement. The system helps organise available data and emission factors, perform calculations and maintain consistency and traceability across the carbon accounting process.