The Research Center for Energy Economics (FfE), today published a study on the Primary Energy Factor (PEF) for electricity and the corresponding CO2 Equivalent Emission Factor (CEEF) applicable to technologies coupling heat and electricity sectors. Read the study in its entirety.


The European Union is building the European Energy Union /EC-01 15/ to ensure that Europe is supplied by secure, affordable and climate-friendly energy. In this context, energy efficiency and reduction of CO2-emissions are prioritised at the EU level as key to realise EU’s energy and climate objectives /EC-02 18/. Correctly measuring efficiency gains and CO2 emission reductions is indispensable to reach the Energy Union objectives and will play an important role in ensuring a level playing field that fairly recognises contributions of all energy solutions accurately. As Europe’s energy transition currently brings especially renewable electricity into the energy supply system, electricity is expected to play a great role in helping different sectors decrease their CO2 emissions.

While security of energy supply and energy costs remain a concern, accurately assessing the environmental impacts of technologies in the energy system is essential to ensure a sound and proportionate EU energy and climate change regulatory framework. The Primary Energy Factor (PEF) for electricity is one of the instruments used by policymakers to assess the efficiency of the electricity. The need for science-based and fit-for-purpose energy efficiency and carbon reduction policies is becoming increasingly relevant to allow a cost-effective energy transition, e.g. for sectors subject to electrification such as the transport sector and heat sector.

Key findings

• The electricity mix displaced by additional generation or used to cover additional electricity demand differs from the yearly average. A “marginal” approach, which more realistically reflects the composition of relevant electricity generation units, more accurately estimates the PEF and CEEF of this specific electricity mixes.
• An average PEF, as proposed by the European Commission in the ongoing Energy Efficiency Directive review, and specific CEEF based on a yearly average electricity generation mix, are not suitable for evaluating the efficiency or carbon intensity of additionally produced or consumed electricity. Using an average approach will overestimate the renewable electricity in the displacement respectively consumption mix. Meanwhile, the marginal approach will more accurately estimate the environmental impact on the electricity system due to additional generation and consumption, signalling more adequately to both policymakers and consumers the environmental impacts of appliances generating or using or this electricity.
• The marginal PEF for the displacement mix excluding the upstream chain, excluding nuclear power plants and including grid losses of 5 % is 2.81 in the EU-28. At national level, the corresponding displacement mix PEFs range from 2.3 to 3.75. Including conversion factors from lower to higher heating value into the calculation, increases the average PEF to 3.26 including nuclear energy and 2.99 excluding nuclear energy.
• The marginal CEEF for the displacement mix is determined including the upstream chain and including grid losses of 5 %. Excluding nuclear power plants this results in a CEEF 986 gCO2/kWhel.
• A separate analysis was carried out on the potential implications of including nuclear power plants, under the assumption that in some countries nuclear power plants may not act as must-run. Including nuclear power plants in the displacement mix results in a higher EU PEF (of 3.17) and a lower EU CEEF (446 gCO2/kWhel)
• Depending on the calculation method used, the PEF for electricity will be impacted differently by an increasing share of renewable electricity. While the PEF of the average generation mix will decrease at a rate reflecting the increase in renewable electricity generation, the decrease of the marginal PEF will be more gradual than the increasing share of renewable electricity. This is because most of the times the residual load (the difference between electricity demand and the supply of wind and sun electricity) in most countries is still positive in the short term. In the medium to long term the development highly depends on the increase in renewable energy
Background and Motivation 5
capacity and the employed load management of additional electricity generation and consumption units.
• The use of PEF and CEEF in climate and energy policymaking is complementary. Both the PEF and CEEF are needed to assess the two-dimensional characteristics in environmental impact (energy savings and reduction of CO2 emissions). PEF and CEER should be determined correctly and include impacts on the energy system transparently. It may be up to the policymaker to favour one of these factors, depending on the priorities at a certain time. Even in an energy system 100 % free of fossil fuels, the PEF is still needed to improve the overall system efficiency, while the CEEF may lose its relevance.

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