What it is about
Part 4‑6 establishes the ERF as an indicator, defines measurement, calculation, and reporting, and distinguishes it from the PUE. It is aimed at data center managers, operations managers, ICT managers, and general contractors who supply waste heat to third parties or plan to do so.
The ERF assesses the quantity of energy supplied, not the efficiency of the process that uses it outside; the standard contains no limit or target value (EN 50600‑4‑6:2020, Introduction and Clause 1).
Core requirements in our own words
The ERF is an annual value between 0 and 1.
It divides the energy reused outside by the total energy consumption of the data center. At 0, nothing is reused; at 1, theoretically everything. Clause 5.
Only what leaves the boundary counts.
Energy reused within the data center lowers the PUE and must not also be counted in the ERF, otherwise it is counted twice. Heated battery rooms or preheated generators result in an ERF of 0. Clause 4, Annex A.3.
The boundary is the same as for the PUE.
It lies at the energy supplier’s point of connection and includes all energy carriers, including natural gas, diesel, or chilled water. Total consumption also includes the infrastructure that brings the heat flow to the point of connection. Clauses 4 and 5.
Measured at the point of connection.
Total consumption is measured at the supplier’s meter, the energy supplied where it passes to another party, usually as heat via temperature and flow rate, converted into kilowatt-hours. Clause 6, Annex B.
What counts is the waste heat at the input of the external system, not what that system delivers.
If a heat pump raises the temperature level, its drive energy is not part of the ERF; if waste heat drives a chiller, the heat counts, not the cooling produced. Annex A.2 and A.5.
A report states boundary, value, type of energy, and end date.
Because of seasonal fluctuations, the value is to be calculated over the year; shorter periods carry the prefix “i” for interim. Clauses 8.1 and 8.3.
From our seminars: two misconceptions
“We heat offices and the battery room with the waste heat, so we have an ERF.”
As long as the heat stays within the boundary, this is an efficiency measure that shows up in the PUE, but it is not an ERF. From seminar practice: operators who supply ancillary spaces in this way act sensibly, but they do not meet any requirement under this standard (Annex A.3.2).
“The district heating output behind the heat pump is our reused energy.”
The standard only counts the waste heat that the data center supplies at the point of connection; the heat pump is a separate system with its own electricity demand. In projects, we often see that raising the heat to district heating level costs more electricity than expected and that the heat customer only needs heat in winter (Annex A.5).
Where Part 4‑6 applies in a project
Site and planning
The ERF depends on a heat customer outside the boundary who can use the heat continuously and at the temperature level supplied; the discussion with the heating network operator belongs in the strategy phase.
Law
The EnEfG requires data centers that start operation from 1 July 2026 to reach a share of reused energy according to DIN EN 50600‑4‑6, staggered by year of commissioning; exemptions apply, among other cases, if a heating network operator does not accept an offer (Section 11(2) and (3)).
Reporting
Commission Delegated Regulation (EU) 2024/1364 requires the waste heat reused according to EN 50600‑4‑6 for the European database on data centers; shares used internally must be deducted (Annex II).
This protects you from a planned share that fails at the system boundary in the German energy efficiency register for data centers (Energieeffizienzregister) (Clause 4).
Status and revision
- Current edition
DIN EN 50600‑4‑6:2020‑07, German edition of EN 50600‑4‑6:2020, approved by CENELEC on 13 January 2020.
- International
ISO/IEC 30134‑6; Commission Delegated Regulation (EU) 2024/1364 refers to EN 50600‑4‑6 as the European implementation.
- Revision
No ongoing revision known. Committee CLC/TC 215, nationally DKE/GK 719.
- Last reviewed
EN 50600‑4‑6
Frequently asked questions
The ratio of the energy reused outside the data center to the total energy consumption, both as annual values. The value is between 0 and 1 (Clause 5).
No. Reuse within the boundary lowers the PUE and is not credited to the ERF (Clause 4).
For data centers starting operation from 1 July 2026, at least 10%; from 1 July 2027, 15%; from 1 July 2028, 20%; in each case no later than two years after commissioning, as an annual average (Section 11(2) EnEfG, as of 13 November 2023).
Both use the same boundary. Internal reuse improves the PUE, external reuse the ERF; for the PUE, the EnEfG disregards the electricity for systems that serve only to upgrade the waste heat (Annex A; Section 11(2) EnEfG).
Operators with an IT power demand of 500 kW or more report the reused energy annually to the European database; the EnEfG requires the share according to DIN EN 50600‑4‑6 as well as the quantity and temperature of the waste heat for the energy efficiency register (Annex 3).
Seminars
Related seminars
- DC-21008
Data Center Sustainability & Efficiency
5 days · In person
Waste heat use with temperature levels, heat pumps, and project examples, as well as a comparison of the indicators with the EnEfG; this saves you a waste heat strategy without a heat customer.
Next date: 7–11 Jun 2027, Munich · GermanPrice plus VAT: €6,990 - DC-21010
Energy Management According to ISO 50001
for data centers under Section 12 EnEfG
3 days · In person
Legally sound implementation of the EnEfG, including the question of where the waste heat goes.
Next date: 8–10 Dec 2026, Frankfurt am Main · GermanPrice plus VAT: €4,195
All prices plus VAT; the price is the same in every format.
- DIN EN 50600‑4‑6:2020‑07 (German edition of EN 50600‑4‑6:2020), Introduction, Clauses 1, 3.1, 3.3, 4, 5, 6, 7, 8.1 to 8.3, Annex A, Annex B
- ISO/IEC 30134‑6
- Commission Delegated Regulation (EU) 2024/1364 of 14 March 2024, Articles 1 and 3, Annexes II and III
- German Energy Efficiency Act (Gesetz zur Steigerung der Energieeffizienz in Deutschland, EnEfG) of 13 November 2023, Section 11, Section 16, Annex 3
- DCE academy seminar practice: Data Center Sustainability & Efficiency (session November 2025), Data Center – General Principles (session April 2026), Energy Management according to DIN EN ISO 50001 (session June 2026)
Glossary terms
- Energy Reuse Factor (ERF)
- energy reuse
- point of connection
- boundary
- total data center energy consumption
- interim ERF (iERF)
- waste heat
- German energy efficiency register for data centers (Energieeffizienzregister)
- European database on data centers
