Average emission factor · Glossary

The average emission factor indicates how many emissions on average are attributable to one unit of energy generated or consumed. In the electricity sector, it is usually stated in grams of CO₂ or grams of CO₂ equivalent per kilowatt hour. It is obtained by dividing the total emissions of a defined electricity mix by the corresponding quantity of electricity. The result is an average value. It indicates how emission-intensive a particular quantity of electricity was overall, not where an individual kilowatt hour came from. It is a special case of the more general concept of the emission factor.

The calculation is simple. How meaningful the result is, however, depends heavily on the system boundary. An average factor can refer to a country's electricity generation or to domestic consumption, in which imports and exports are taken into account. It can apply to a year, a month or an hour, or to the contractually stated supply mix of a supplier. The emission category that is counted must also be specified. Often only the direct CO₂ emissions from combustion in power plants are meant. CO₂ equivalents additionally cover other greenhouse gases such as methane and nitrous oxide, converted according to their climate impact. If upstream chains are included, emissions from fuel extraction, transport and processing are added. Depending on the system boundary, this may also include plant construction and disposal.

Unit of measurement and reference value

The unit g CO₂/kWh or g CO₂e/kWh relates a quantity of emissions to a quantity of energy. The kilowatt hour is a quantity of energy and not an instantaneous power. A device with a power of one kilowatt that runs for one hour consumes one kilowatt hour. A calculation example: if a household consumes 2,500 kWh per year and an average factor of 344 g CO₂/kWh is applied, the result is roughly 860 kilograms of CO₂ by calculation. This quantity is attributed to the consumption. It is not measured physically.

It is important whether the factor refers to generated or to consumed electricity. The generation mix shows which power plants produced electricity domestically. The consumption mix may differ from it because electricity flows across borders. In the closely interconnected European electricity market, this is more than a statistical nicety. The German Environment Agency (Umweltbundesamt, UBA) explicitly cites, as one reason for the decline in the German factor in 2025, that Germany imported more electricity than it exported. A lower emission intensity can therefore also result from generation having been shifted abroad.

The time period also changes the value. An annual average smooths out large differences: between windy nights, sunny midday hours and periods of Dunkelflaute (prolonged low wind and solar output). For an annual balance, an annual factor may be sufficient. If, by contrast, one wants to know whether flexible consumption can be shifted into lower-emission hours, hourly resolved factors are more meaningful.

Values for Germany

The Umweltbundesamt calculates the CO₂ emission factor of the German electricity mix every year and publishes the time series from 1990. This indicator covers the direct CO₂ emissions of electricity generation per kilowatt hour of electricity consumed domestically. For 2025, the UBA estimates 344 g CO₂/kWh. In 2024 it was 353 g and in 2023 it was 379 g. Around 1990, the value was about 765 g/kWh. As reasons for the decline, the UBA cites the growing share of renewable energies, the decline in electricity consumption as a result of economic stagnation, and the import surplus. In the UBA's assessment, the further decrease since 2023 therefore shows only to a limited extent that climate protection measures in the electricity sector are having a lasting effect. Values for 2025 are provisional and may be adjusted later.

The same UBA publication contains further indicators, for example factors that include greenhouse gases other than CO₂ as CO₂ equivalents and that include upstream chains. These are higher than the pure direct CO₂ value. Anyone who takes a factor from a table should therefore always check which variant is meant and which year it refers to.

Distinction from the marginal emission factor

The average factor is often confused with the marginal emission factor. The average factor distributes the emissions of an entire mix evenly across all kilowatt hours. The marginal factor, by contrast, describes how many emissions are additionally caused or avoided when consumption changes by one kilowatt hour in a specific situation. In the short term, what matters is which power plant at the margin of the merit order adjusts its output. This may be a gas-fired or a coal-fired power plant. In hours when wind or solar power is curtailed, additional consumption may even use electricity that would otherwise be lost.

For a household's annual balance, the average value is usually a usable approximation. If a heat pump, an electric car or an electrolyser is deliberately operated at particular times, it is not sufficient to assess the short-term climate impact. Long-term effects additionally depend on whether the new demand triggers the construction of new plants and, if so, which ones.

Corporate carbon footprints

In carbon footprints, the average factor is a practical tool. One multiplies electricity consumption by the factor and obtains a calculated quantity of emissions. For Scope 2 emissions, the Greenhouse Gas Protocol distinguishes two methods. The location-based method uses the average emission intensity of the grid on which consumption takes place. The market-based method relies on contracts, supplier information and certificates. A residual mix applies to the part not covered. In October 2025, the GHG Protocol put a revised Scope 2 methodology out for consultation. For the location-based method, it proposes a hierarchy of factors by spatial and temporal accuracy, up to hourly values. In the market-based method, general grid average factors are no longer to be permitted as a substitute value. Whether and in what form these proposals are finally adopted must be checked before application.

Electricity labelling in Germany

Average values also play a role in electricity labelling. Under Section 42 of the Energy Industry Act (Energiewirtschaftsgesetz, EnWG), electricity suppliers in Germany must state two things on invoices, in advertising material and on their website. First, the share of energy sources in their total energy source mix in the last or the year before last. From 1 July at the latest, the values of the previous year apply. Second, information on environmental impacts, at least on CO₂ emissions and radioactive waste. If suppliers offer different products, this applies correspondingly to each product and to the remaining mix. The data are reported annually to the Federal Network Agency (Bundesnetzagentur). Insofar as the disclosure of electricity from renewable energies is concerned, the Umweltbundesamt may verify its accuracy. This presentation is based on the version that has applied since 23 December 2025.

The attribution stated follows accounting and proof rules, in particular the cancellation of guarantees of origin. It does not follow the physical flow of electricity. Anyone who buys a green electricity tariff continues to receive electricity physically from the common grid. The CO₂ value of a supply product must therefore be read differently from the grid's average factor. Anyone who applies the grid average and certificates at the same time in a carbon footprint risks double counting.

Typical misunderstandings

The factor does not apply to every individual kilowatt hour. Grid electricity cannot be physically divided by origin. The factor is a calculated attribution for a defined quantity.
A low average does not mean that additional consumption is automatically climate-friendly. A low annual value says little about a tight winter evening hour. As electrification of heating, transport and industry increases, this question becomes more important.
Intensity is not the same as quantity. A falling factor can go hand in hand with high absolute emissions. Conversely, rising electricity consumption can reduce total emissions if it replaces oil, gas or coal in other sectors. To assess this, one must keep final energy, primary energy and conversion losses clearly apart.
A falling factor can also result from lower consumption or higher imports. For 2025, the UBA explicitly cites both effects alongside the expansion of renewable energies.

Role in the electricity system

The average factor is a compact indicator of the decarbonisation of electricity generation. It falls when renewable energies displace fossil power plants. Fossil power plants differ greatly in this respect: lignite and hard coal have significantly higher specific emissions than a modern gas-fired power plant. The effect of more gas-fired generation therefore depends on what it replaces. If it replaces coal-fired electricity, the factor tends to fall. If, on the other hand, gas replaces missing wind or solar power, the factor rises.

The average does not capture many operational questions: load flows, grid bottlenecks, balancing energy, price formation and security of supply. This becomes particularly clear with flexibility. Whether shifting consumption into hours with plenty of wind or sun reduces emissions depends on which generation is actually displaced and on whether grid bottlenecks limit the use of renewable energy. This requires time-resolved data and a look at the residual load.

Overall, the average emission factor is a value for accounting and comparisons. It is suitable for reports, product footprints and monitoring political targets, provided that the data source, system boundary, greenhouse gas scope and time period are stated. To assess individual decisions, new consumers or flexible modes of operation, it must be supplemented by marginal, temporal and spatial information.

Sources

CO₂-Emissionen pro Kilowattstunde Strom 2025 nur leicht gesunken — Umweltbundesamt; unbekannt (2026). Meldung, Einleitung und Ursachenbeschreibung
Climate Change 16/2026: Entwicklung der spezifischen Treibhausgas-Emissionen des deutschen Strommix in den Jahren 1990–2025 — Umweltbundesamt; 2026-03 (laut Ablagepfad). Kapitel 1.3, 2.1, 2.2; Tabellen 1 und 3
Energiewirtschaftsgesetz § 42 Stromkennzeichnung, Transparenz der Stromrechnungen, Verordnungsermächtigung — Bundesministerium der Justiz / juris; unbekannt (konsolidierte Fassung). § 42 Abs. 1 Nr. 1 und 2, Abs. 3, Abs. 7
Public Consultation Scope 2 — Greenhouse Gas Protocol; 2025-10. Abschnitte 3 und 4 (location-based method), Restmix-Regeln
EnWG § 42 (NWB Gesetze) — NWB Verlag; unbekannt. Redaktionelle Anmerkung zur Fassung

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Edited by eCMS on 11.11.2026 19:42