What are emission factors and where do they come from?

An emission factor is a value that indicates the climate impact a specific activity or purchase generates. It is the mathematical link between something measurable — kilowatt-hours, litres of diesel, money spent on office supplies — and an emissions value in carbon dioxide equivalents (CO₂e). Without emission factors, it would be impossible to calculate a company's carbon footprint at any meaningful scale.

Where do emission factors come from?

Emission factors are built on research, national emissions statistics, and scientific databases. They cover different types of greenhouse gases — not just carbon dioxide but also methane, nitrous oxide, and fluorinated gases — since all are converted into a common measure: CO₂e. An important part of working with emission factors involves keeping them updated as energy mixes change and new research emerges.

GoClimate develops and maintains its own emission factors, based on established national and international data sources and tailored to the industries and purchasing categories most relevant to Swedish companies. This means the emission factors that calculate your carbon footprint in GoClimate's tool are customised for Swedish conditions — not generic global averages.

Two different types of emission factors

There are fundamentally two types of emission factors, depending on which data is used as input.

The first type is used in activity-based calculations. Here the starting point is the actual physical activity: how many litres of diesel were refuelled, how many kilowatt-hours of electricity were consumed, how many tonne-kilometres the freight was transported. The emission factor indicates the climate impact per physical unit — for example kg CO₂e per litre of diesel or per kWh. This method delivers high precision but requires the company to collect detailed activity data per purchase, which can quickly prove time-consuming to scale.

The second type is used in spend-based calculations. Here money is the input: how much did we pay, and to which supplier category? Emission factors per category are expressed in kg CO₂e per krona spent, and emissions are then calculated by multiplying by the amount.

Simply put: activity-based emission factors measure what happened physically. Spend-based emission factors start from what it cost and work backwards from there.

How are emission factors used in practice?

The GHG Protocol — the standard most climate frameworks are built on — ranks calculation methods in a data hierarchy with four levels: from supplier-specific primary data at the top, through hybrid methods and activity-based average emission factors, down to spend-based at the bottom². Spend-based emission factors are therefore the last resort in the methodology hierarchy, not an equivalent alternative. The standard is currently under active revision with greater emphasis on primary data³.

In practice, this means the different methods are often mixed: direct emissions from own vehicles and premises are calculated using activity-based emission factors, while purchased goods and services are calculated using spend-based factors. Both types are used in parallel, and together they provide a complete picture of emissions without requiring resources that most SMEs shouldn't need to spend.

Why does understanding the difference matter?

An emission factor is never exact — it is a well-founded estimate based on average data. A purchase of electricity is assigned an average value per kWh, regardless of whether the supplier in Sweden uses one hundred percent wind power or fossil production. The climate impact per product or service may therefore differ from what the factor indicates.

This means emission factors also vary in precision. Supplier-specific emission factors — where a supplier shares their actual climate data — provide the highest accuracy and lowest uncertainty. Average emission factors offer lower precision but instead cover the entire value chain without requiring individual supplier dialogue. Which part of the chain to prioritise depends on where the company's emissions are greatest.

As climate reporting matures and more suppliers begin sharing their own climate data, calculations can be refined with more accurate primary data. But the foundation — systematically linking activities and purchases to emissions values through standardised emission factors — remains the same.

Emission factors as a starting point

There is no "perfect" emission factor. But there is a significant difference between not measuring at all and starting with the emission factors and data that are already available.

Emission factors are not the final destination — they are the starting point. They give a company an answer to the fundamental question: what is generating our emissions, and where is the greatest opportunity to reduce climate impact? From there, more targeted action can follow — with better data, closer supplier dialogue, and over time a transition toward activity-based emission factors for the most important categories.

Want to see which emission factors are calculating your company's climate impact?

GoClimate's tool automatically links your purchases to the right emission factors and calculates emissions — with no manual work required.

Try GoClimate here →