What it is about
Part 4‑2 establishes the PUE as a key performance indicator, defines three measurement categories, governs measurement, calculation, and reporting, and gives guidance on interpretation. It is a tool for energy management: identifying improvements in operation and assessing design and processes over time. The PUE relates only to the infrastructure within the data center boundary.
It does not cover the efficiency of the IT itself, its productivity, renewable energy, or the reuse of waste heat (EN 50600‑4‑2:2019, Clauses 1 and 4).
Core requirements in our own words
The PUE is an annual value and always greater than 1.
It is the ratio of the total data center energy consumption to the IT equipment energy consumption, both over the same year in kilowatt-hours. Total consumption includes all forms of energy at the boundary, including natural gas or purchased chilled water. Clauses 3.1.3, 3.1.7 and 5.1.
The meter marks the boundary.
Total consumption is measured at the energy supplier’s point of connection. IT energy includes storage, processing, and transmission equipment; total consumption additionally includes power supply, cooling, lighting, and security systems. Clauses 5.1 and 6.2.1, Annex A.
Three categories by where the IT energy is measured.
Category 1 measures at the UPS output, category 2 at the output of the power distribution units, category 3 at the input of the IT equipment. The closer to the load, the more accurate the value; non-IT loads must be kept out of the IT energy. Clauses 6.2.1 to 6.2.5.
Without category and period, a PUE value is meaningless.
A report states the data center with its boundary, the value, the category as a subscript, and the end date of the measurement period. Values covering less than one year must be labeled as interim PUE. Clause 7.1.1, Annex C.2.
Derivatives supplement the PUE but do not replace it.
Partial PUE assesses a subsystem such as power distribution or cooling, interim PUE a shorter period, design PUE a planned data center. Each derivative must be labeled and documented with boundary, period, and assumptions. Annex C.
The PUE shows the development, not the ranking.
The indicator is meant to show how a facility develops over time and the effect of design and operational decisions. Values of different data centers should not be compared directly, because climate, utilization, Availability Class, and business purpose shape the result. Annexes A and D.
From our seminars: two misconceptions
“Our PUE is 1.3 today.”
A snapshot value is not a PUE in the sense of the standard; the indicator is an annual value from continuous measurement. Shorter periods and real-time values must be labeled as interim PUE. In projects, we often see a winter value passed on as the annual indicator (Clauses 3.1.3, 3.1.7, Annex C.2).
“We used less energy, so our PUE has improved.”
If the IT load falls more than the total consumption, for example after a server migration, the PUE rises even though fewer kilowatt-hours were consumed; fixed consumption and part-load operation of the cooling weigh more heavily in the ratio. From seminar practice: an auditor will then ask not about the kilowatt-hours but about the causes of the deterioration (Clause 4; seminar exercise).
Where Part 4‑2 applies in a project
Measurement concept
Meters are placed so that category and boundary are unambiguous; for the European database on data centers, Commission Delegated Regulation (EU) 2024/1364 requires the IT energy according to category 1 at the UPS (Annex II).
Reporting obligation
Operators with an IT power demand of 500 kW or more report annually by 15 May to the European database (Articles 1 and 3 of the Regulation); the EnEfG requires the indicator annually by 31 March for the German energy efficiency register for data centers (Energieeffizienzregister) and sets limits from July 2027 (Sections 11 and 13, Annex 3).
Energy management
Partial PUE values per subsystem show the effect of individual measures (Annex C.3).
This protects you from reporting a value that fails the audit because of the measurement category. It saves you from having to explain why the PUE got worse even though consumption went down.
Status and revision
- Current edition
DIN EN 50600‑4‑2:2019‑08, German edition of EN 50600‑4‑2:2016 with corrigendum AC:2017 and amendment A1:2019. The EnEfG and the Regulation refer to this edition.
- International
ISO/IEC 30134‑2:2016; since January 2026, the second edition ISO/IEC 30134‑2:2026 has been available, and the European version has not yet been aligned with it.
- Revision
Alignment with the second ISO edition is to be expected; as of our status in September 2026, no date is known. Committee CLC/TC 215, nationally DKE/GK 719.
- Last reviewed
EN 50600‑4‑2
Frequently asked questions
The ratio of a data center’s annual total energy consumption to the annual energy consumption of its IT equipment, both in kilowatt-hours. The value is always greater than 1 (Clauses 3.1.3, 5.1).
Three, by where the IT energy is measured: category 1 at the UPS output, category 2 at the output of the power distribution units, category 3 at the input of the IT equipment (Clause 6.2).
The standard advises against it. The PUE serves to track one data center over time; comparisons between sites are only meaningful with context on climate, utilization, availability, and measurement category (Clause 4, Annex D).
For data centers that started operation before 1 July 2026, a maximum of 1.5 from 1 July 2027 and a maximum of 1.3 from 1 July 2030, each as an annual average; for data centers commissioned later, a maximum of 1.2. The basis of calculation is DIN EN 50600‑4‑2 (Section 11 and Annex 3 EnEfG, as of 13 November 2023).
Operators of data centers with an IT power demand of 500 kW or more, annually by 15 May for the previous year, under Commission Delegated Regulation (EU) 2024/1364 (Articles 1 and 3).
Seminars
Related seminars
- DC-21008
Data Center Sustainability & Efficiency
5 days · In person
The indicators of the 4-x series with calculation, measurement concept, and the link to the EnEfG and the European reporting obligation; this saves you a report that is based on the wrong measuring point.
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 with case exercises on the PUE, including the case in which lower consumption produces a worse indicator.
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 50600‑4‑2:2019‑08 (German edition of EN 50600‑4‑2:2016 with AC:2017 and A1:2019), European foreword, national foreword of the German edition, Clauses 1, 3.1, 4, 5.1, 6.2.1 to 6.2.5, 7.1, Annex A, Annex C, Annex D, national Annex NC of the German edition
- Commission Delegated Regulation (EU) 2024/1364 of 14 March 2024, Articles 1 and 3, Annex II
- German Energy Efficiency Act (Gesetz zur Steigerung der Energieeffizienz in Deutschland, EnEfG) of 13 November 2023, Sections 11, 13, Annex 3
- ISO/IEC 30134‑2:2016; ISO/IEC 30134‑2:2026 (catalog entry retrieved 2026‑09‑17)
- DCE academy seminar practice: Data Center – General Principles (session April 2026), Data Center Sustainability & Efficiency (session November 2025), Energy Management according to DIN EN ISO 50001 (materials June 2026)
Glossary terms
- Power Usage Effectiveness (PUE)
- total data center energy consumption
- IT equipment energy consumption
- boundary
- PUE category 1 to 3
- partial PUE (pPUE)
- interim PUE (iPUE)
- design PUE (dPUE)
- power usage effectiveness under the EnEfG (Energieverbrauchseffektivität)
- German energy efficiency register for data centers (Energieeffizienzregister)
- European database on data centers
- power distribution unit (PDU)
