EN 17423 (on reporting Prim.En.Factors + CO2)

Energy performance of buildings – Determination and reporting of Primary Energy Factors (PEF) and CO2 emission coefficient – General Principles, Module M1-7

CEN standards database


Geographical scope:
EP indicators, requirements or ratings
Published date:
Nov. 15, 2020
  • Overarching
CEN and/or ISO


This document provides a transparent framework for reporting on the choices related to the procedure to determine PEFs and CO2 Emission coefficients for energy delivered to and/or exported by the buildings as described in EN ISO 52000-1:2017. Exported PEFs and CO2 Emission coefficients can be different from those chosen for delivered energy.
This document can be considered as a supporting/complementing standard to EN ISO 52000-1, as the latter requires values for the PEFs and GHG Emissions factors to complete the EPB calculation.

NOTE : This CEN standard was the basis for the ISO standard ISO 52000-3:2023. Both standards are largely identical. As long as there is no initiative to prepare a common CEN and ISO standard, EN 17423 should be used for application in Europe.


Why is this standard important?

By: Johann ZIRNGIBL (CEN TC371/WG1)

The values of primary energy factors (PEFs) and CO2 Emission factors have a strong impact on the expression of the energy performance of buildings as they are the multiplication factors for the whole calculated building energy use according to EN ISO 52000-1. Primary energy is the key indicator for the energy performance of building requested by the European Energy Performance of Building Directive (EPBD).

The quality and transparency of the PEF calculations is key for the:

  • reliability of primary energy consumption or the primary energy savings in buildings,
  • fair competition between energy saving technologies using different fuels,
  • consistency of cost-optimisation,
  • definitions of Nearly Zero Energy Buildings (NZEB).

Therefore, there is a need for transparency related to the choices that have been made to determine the content of the PEF and the related CO2 emission factors. The purpose of EN 17423 is not to standardize the value of the PEF or CO2 emission factors, but to make clear which assumptions were used to determine these factors.
Annex B of EN ISO 52000-1 provides some first information on assumptions used. EN 17423 enlarges the assumptions, for example by several internationally recognized conventions for the primary energy content of electricity from renewable or nuclear sources, biogenic carbon, energy exchanges between geographical perimeters.