ISO/IEC 30134-7

Information technology — Data centres key performance indicators — Part 7: Cooling efficiency ratio (CER)

This document specifies the cooling efficiency ratio (CER) as a key performance indicator (KPI) for quantifying the efficient use of energy to control the temperature of spaces within a data centre (DC). This document: a) defines the CER of a DC; b) describes the relationship of this KPI to a DC’s infrastructure, information technology equipment and information technology operations; c) defines the measurement, the calculation and the reporting of the parameter; and d) provides information on the correct interpretation of the CER. Annex A describes the correlation of the CER and other KPIs. Annex B provides examples of the usage of the CER. Annex C introduces the parameters that affect the CER. Annex D describes requirements and recommendations for derivatives of KPIs associated with the CER. This document is not applicable to cooling systems that are not powered by electricity (e.g. heat-driven absorption chillers).

Titre manque — Partie 7: Titre manque

General Information

• Status: Not Published
• ICS: 35.020 - Information technology (IT) in general
• ICS: 91.120.10 - Thermal insulation of buildings
• Technical Committee: ISO/IEC JTC 1/SC 39 - Sustainability, IT and data centres
• Drafting Committee: ISO/IEC JTC 1/SC 39/WG 1 - Resource Efficient Data Centres
• Current Stage: 6000 - International Standard under publication
• Completion Date: 10-Feb-2023

Standards Content (Sample)

Style Definition
ISO/IEC 30134-7:20222023(E)
...
Formatted: Font: 11 pt, English (United Kingdom)
ISO IEC JTC 1/SC 39/WG 1
Formatted
...
Date: 2022-11-122023-01-13 Formatted: zzCover, Left
Formatted: English (United Kingdom)

Information technology — Data centres key performance indicators — Part 7: Cooling efficiency

Formatted: zzCover, Left, Space After: 0 pt
ratio (CER)
Formatted: Font: 11 pt
Formatted: zzCover, Line spacing: single
DIS stage
Warning for WDs and CDs

This document is not an ISO International Standard. It is distributed for review and comment. It is subject to

change without notice and may not be referred to as an International Standard.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of

which they are aware and to provide supporting documentation.
© ISO #### – All rights reserved
---------------------- Page: 1 ----------------------
© ISO 2022
---------------------- Page: 2 ----------------------
ISO/IEC DIS 30134-7:20222023(E)
© ISO 2023

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part

Formatted: Font: 11 pt, Font color: Blue

of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or

Formatted: Border: Box: (Single solid line, Blue, 0.5 pt

mechanical, including photocopying, or posting on the internet or an intranet, without prior written

Line width)

permission. Permission can be requested from either ISO at the address below or ISO’s member body

in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Formatted: Font: 11 pt, Font color: Blue, English (United
Kingdom)
Email: [e-mail]
Formatted: Font: 11 pt, Font color: Blue
Website: www.iso.orgwww.iso.org
Formatted: Font: 11 pt, Font color: Blue, English (United
Kingdom)
Published in Switzerland
Formatted: Font: 11 pt, Font color: Blue, English (United
Kingdom)
Formatted: Font: 11 pt
Formatted: Space After: 0 pt, Line spacing: single
iv © ISO #### – All rights reserved
iv © ISO/IEC 2023 – All rights reserved
---------------------- Page: 3 ----------------------
ISO/IEC DIS 30134-7:20222023(E)
Formatted: Space Before: 48 pt, Don't adjust space
Contents
between Latin and Asian text, Don't adjust space
between Asian text and numbers

Foreword ................................................................................................................................................................. v

Introduction .......................................................................................................................................................... vi

1 Scope .......................................................................................................................................................... 1

2 Normative references .......................................................................................................................... 1

3 Terms, definitions and abbreviations ............................................................................................ 1

3.1 Terms and definitions .......................................................................................................................... 1

3.2 Abbreviated terms ................................................................................................................................ 2

3.3 Symbols ..................................................................................................................................................... 2

4 Applicable area of the data centre ................................................................................................... 3

5 Definition of the CER ............................................................................................................................. 3

6 Measurement of CER ............................................................................................................................. 4

6.1 General ...................................................................................................................................................... 4

6.2 Requirements .......................................................................................................................................... 4

6.3 Recommendations ................................................................................................................................. 5

7 Application of CER ................................................................................................................................. 5

8 Reporting of CER .................................................................................................................................... 5

8.1 Requirements .......................................................................................................................................... 5

8.1.1 Standard construct for communicating CER ................................................................................ 5

8.1.2 Data for public reporting of CER ...................................................................................................... 5

8.2 Recommendations ................................................................................................................................. 6

Annex A (informative) Correlation of CER and other KPIs .................................................................. 8

A.1 General ...................................................................................................................................................... 8

A.2 Discussion of existing terms for performance rating ............................................................... 8

Annex B (normative) Examples of usage of CER ................................................................................... 10

B.1 Determining PUE in data centres with different computer rooms using CER .............. 10

B.2 Determining CER in cases of energy re-use ............................................................................... 10

Annex C (informative) Parameters influencing CER ........................................................................... 11

C.1 Adjustment of temperature ............................................................................................................ 11

C.2 Demand of cooling .............................................................................................................................. 11

Annex D (normative) Derivatives of CER ................................................................................................ 12

D.1 Purpose of CER derivatives ............................................................................................................. 12

D.2 Using CER derivatives ....................................................................................................................... 12

D.3 Interim CER ........................................................................................................................................... 12

D.4 Determination of CPR ........................................................................................................................ 12

Formatted: Font: 11 pt

D.4.1 Calculation of CPR ............................................................................................................................... 12

Formatted: Space After: 0 pt, Line spacing: single
© ISO #### – All rights reserved v
© ISO/IEC 2023 – All rights reserved v
---------------------- Page: 4 ----------------------
ISO/IEC DIS 30134-7:20222023(E)

D.4.2 Measurement of CER ..........................................................................................................................13

D.4.2.1 Requirements .......................................................................................................................................13

D.4.2.2 Recommendations ..............................................................................................................................13

D.4.3 Reporting of CER ..................................................................................................................................13

D.4.3.1 Requirements .......................................................................................................................................13

D.4.3.2 Recommendations ..............................................................................................................................13

D.4.4 Using CPR in capacity management ..............................................................................................13

D.5 Determination of CEF .........................................................................................................................13

D.5.1 Calculation of CEF ................................................................................................................................13

D.5.2 Partial CEF ..............................................................................................................................................14

D.5.3 Example ..................................................................................................................................................14

Bibliography ........................................................................................................................................................16

Foreword ............................................................................................................................................................ viii

Introduction ......................................................................................................................................................... ix

1 Scope .......................................................................................................................................................... 1

2 Normative references .......................................................................................................................... 1

3 Terms, definitions and abbreviations ........................................................................................... 1

3.1 Terms and definitions ......................................................................................................................... 1

3.2 Abbreviated terms ................................................................................................................................ 2

3.3 Symbols ..................................................................................................................................................... 3

4 Applicable area of the data centre .................................................................................................. 3

5 Definition of the CER ............................................................................................................................ 4

6 Measurement of CER ............................................................................................................................ 6

6.1 General ...................................................................................................................................................... 6

6.2 Requirements ......................................................................................................................................... 6

6.3 Recommendations ................................................................................................................................ 6

7 Application of CER ................................................................................................................................. 6

8 Reporting of CER .................................................................................................................................... 6

8.1 Requirements ......................................................................................................................................... 6

8.1.1 Standard construct for communicating CER ............................................................................... 6

8.1.2 Data for public reporting of CER ...................................................................................................... 7

8.2 Recommendations ................................................................................................................................ 8

Annex A (informative) Correlation of CER and other KPIs ................................................................10

Annex B (normative) Examples of usage of CER....................................................................................12

Annex C (informative) Parameters influencing CER............................................................................14

Annex D (normative) Derivatives of CER .................................................................................................15

Formatted: Font: 11 pt

Bibliography ........................................................................................................................................................20 Formatted: Space After: 0 pt, Line spacing: single

vi © ISO #### – All rights reserved
vi © ISO/IEC 2023 – All rights reserved
---------------------- Page: 5 ----------------------
ISO/IEC DIS 30134-7:20222023(E)
Formatted: Don't adjust space between Latin and Asian
text, Don't adjust space between Asian text and
numbers
Formatted: Font: 11 pt
Formatted: Space After: 0 pt, Line spacing: single
© ISO #### – All rights reserved vii
© ISO/IEC 2023 – All rights reserved vii
---------------------- Page: 6 ----------------------
ISO/IEC DIS 30134-7:20222023(E)
Foreword

ISO (the International Organization for Standardization) and IEC (the International Electrotechnical

Commission) form the specialized system for worldwide standardization. National bodies that are

members of ISO or IEC participate in the development of International Standards through technical

committees established by the respective organization to deal with particular fields of technical activity.

ISO and IEC technical committees collaborate in fields of mutual interest. Other international

organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the

work.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of document should be noted. This document was drafted in accordance with the editorial

rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives or
www.iec.ch/members_experts/refdocs).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. Details

of any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC list of patent

declarations received (see https://patents.iec.ch).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the World

Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see

www.iso.org/iso/foreword.html. In the IEC, see www.iec.ch/understanding-standards.

This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,

Subcommittee SC 39, Sustainability, IT and data centres.
Formatted: English (United Kingdom)

A list of all parts in the ISO/IEC 30134 series can be found on the ISO and IEC websites.

Formatted: English (United Kingdom)

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html and www.iec.ch/national-

committees.
Formatted: Font: 11 pt
Formatted: Space After: 0 pt, Line spacing: single
viii © ISO #### – All rights reserved
viii © ISO/IEC 2023 – All rights reserved
---------------------- Page: 7 ----------------------
ISO/IEC DIS 30134-7:20222023(E)
Formatted: No page break before, Don't adjust space
Introduction
between Latin and Asian text, Don't adjust space
between Asian text and numbers

The global economy is today reliant on information and communication technologies and the associated

Formatted: Body Text, Don't adjust space between Latin

generation, transmission, dissemination, computation and storage of digital data. All markets have

and Asian text, Don't adjust space between Asian text

experienced exponential growth in that data, for social, educational and business sectors and, while the

and numbers

internet backbone carries the traffic, there are a wide variety of data centres at nodes and hubs within

both private enterprise and shared/collocation facilities.

The historical data generation growth rate exceeds the capacity growth rate of information and

communications technology hardware and, with less than half (in 2014) of the world’s population having

access to an internet connection, that growth in data can only accelerate. In addition, with many

governments having “digital agendas” to provide both citizens and businesses with ever-faster

broadband access, the very increase in network speed and capacity will, by itself, generate ever more

usage (Jevons Paradox). Data generation and the consequential increase in data processing and storage

are directly linked to increasing power consumption.

With this background, data centre growth, and power consumption in particular, is an inevitable

consequence; this growth will demand increasing power consumption despite the most stringent energy

efficiency strategies. This makes the need for key performance indicators (KPIs) that cover the effective

use of resources (including but not limited to energy) and the reduction of CO2 emissions essential.

Within the ISO/IEC 30134 series, the term “resource usage effectiveness” is more generally used for KPIs

Formatted: std_publisher

in preference to “resource usage efficiency”, which is restricted to situations where the input and output

Formatted: std_docNumber
parameters used to define the KPI have the same units.
Formatted: std_docPartNumber

The cooling efficiency ratio (CER) allows data centre operators to quickly determine the efficiency of their

data centre cooling system, compare the results, and determine if energy efficiency improvements need

to be made. The impact of operational cooling efficiency is proving to be extremely important in the

design, location and operation of current and future data centres.

In order to determine the overall resource efficiency of a data centre, a holistic suite of metrics is required.

This document is one of a series of International Standards for such KPIs and has been produced in

accordance with ISO/IEC 30134-1, which defines common requirements for a holistic suite of KPIs for

Formatted: std_publisher

data centre resource efficiency. This document does not specify limits or targets for the KPI and does not

Formatted: std_docNumber

describe or imply, unless specifically stated, any form of aggregation of this KPI into a combination with

Formatted: std_docPartNumber

other KPIs for data centre resource efficiency. This document presents specific rules on CER’s use, along

with its theoretical and mathematical development. This document concludes with several examples of

site concepts that could employ the CER metric.
Formatted: Font: 11 pt
Formatted: Space After: 0 pt, Line spacing: single
© ISO #### – All rights reserved ix
© ISO/IEC 2023 – All rights reserved ix
---------------------- Page: 8 ----------------------
INTERNATIONAL STANDARD ISO/IEC 30134-7:2023(E)
Formatted: Font color: Blue
Information technology — Data centres key performance
Formatted: Different first page header
indicators —
Formatted: Font color: Blue
Part 7:
Formatted: Font: Bold, Font color: Blue
Formatted: Font color: Blue
Cooling efficiency ratio (CER)
Formatted: Space Before: 20 pt, Don't adjust space
between Latin and Asian text, Don't adjust space
between Asian text and numbers
1 Scope Formatted: Don't adjust space between Latin and Asian
text, Don't adjust space between Asian text and
numbers

This document specifies the cooling efficiency ratio (CER) as a key performance indicator (KPI) for

quantifying the efficient use of energy to control the temperature of spaces within thea data centre (DC).

Formatted: List Number 1, Don't adjust space between
Latin and Asian text, Don't adjust space between Asian
This document:
text and numbers, Tab stops: 0.7 cm, Left + 1.4 cm, Left

a) defines the CER of a DC; + 2.1 cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm,

Left + 4.9 cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7

b) describes the relationship of this KPI to a DC’s infrastructure, information technology equipment cm, Left

and information technology operations;
Formatted: cite_app
Formatted: Don't adjust space between Latin and Asian

c) defines the measurement, the calculation and the reporting of the parameter; and

text, Don't adjust space between Asian text and
numbers
d) provides information on the correct interpretation of the CER.
Formatted: cite_app
Annex A describes the correlation of the CER and other KPIs.
Formatted: cite_app
Annex B provides examples of the usage of the CER.
Formatted: cite_app
Annex C introduces the parameters that affect the CER.
Formatted: cite_app

Annex D describes requirements and recommendations for derivatives of KPIs associated with the CER. Formatted: cite_app

Formatted: cite_app

This document is not applicable to cooling systems that are not powered by electricity (e.g. heat-driven

absorption chillers).
Formatted: cite_app
Formatted: English (United States)
2 Normative references
Formatted: std_publisher
Formatted: RefNorm, Don't adjust space between Latin

The following documents are referred to in the text in such a way that some or all of their content

and Asian text, Don't adjust space between Asian text

constitutes requirements of this document. For dated references, only the edition cited applies. For

and numbers, Tab stops: 0.7 cm, Left + 1.4 cm, Left +

undated references, the latest edition of the referenced document (including any amendments) applies.

2.1 cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left

ISO/IEC 30134-1, Information technology — Data centres — Key performance indicators — Part 1:

+ 4.9 cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm,
Overview and general requirements Left
Formatted: std_docNumber
Formatted: std_docPartNumber
3 Terms, definitions and abbreviations
Formatted: std_docTitle, Font: Not Italic
3.1 Terms and definitions
Formatted: Don't adjust space between Latin and Asian
text, Don't adjust space between Asian text and

For the purposes of this document, the terms and definitions given in ISO/IEC 30134-1 and the following

numbers
apply.
Formatted
...
© ISO/IEC 2023 – All rights reserved 1
---------------------- Page: 9 ----------------------
ISO/IEC 30134-7:2023(E)
Formatted: Space After: 36 pt, Line spacing: Exactly 12
Formatted: Font: 12 pt

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
Formatted: Don't adjust space between Latin and Asian
3.1.1
text, Don't adjust space between Asian text and
cooling efficiency ratio
numbers
CER
Formatted: Don't adjust space between Latin and Asian
ratio of total heat removed and electrical energy used by a cooling system
text, Don't adjust space between Asian text and
numbers

Note 1 to entry: The value of "total heat annual removed" from the DC is measured in kWh.

Formatted: Don't adjust space between Latin and Asian
3.1.2 text, Don't adjust space between Asian text and
numbers, Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1
cooling performance ratio
cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left +
CPR
4.9 cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left
ratio of actual heat load and electrical power used by a cooling system
Formatted: Don't adjust space between Latin and Asian
Note 1 to entry: The actual heat load is measured in kW.
text, Don't adjust space between Asian text and
numbers
3.1.3
Formatted: Don't adjust space between Latin and Asian
energy loss
text, Don't adjust space between Asian text and
dissipation of energy caused by electric utilities
numbers
Formatted
Note 1 to entry: The energy loss turned into heat are measured in kWh. ...
Formatted
...

Note 2 to entry: Energy loss is caused, for example. by transformers, uninterruptible power supply (UPS), fans of

Formatted
computer room air handling units (CRAH), pumps, lighting, power cables. ...
Formatted
...
3.2 Abbreviated terms
Formatted
...
Formatted: std_publisher

For the purposes of this document, the terms and definitions given in ISO/IEC 30134-1 and the following

apply.
Formatted: std_docNumber
CEF cooling efficiency factor Formatted: std_docPartNumber
Formatted
CER cooling efficiency ratio ...
Formatted
COP coefficient of performance ...
Formatted
...
CPR cooling performance ratio
Formatted
...
DC data centre
Formatted
...
EER energy efficiency ratio
Formatted
...
HVAC heating, ventilation, air conditioning
Formatted
...
iCER interim cooling efficiency ratio
Formatted
...

NSenCOP Net Sensible Coefficient of Performancenet sensible coefficient of performance

Formatted
...
PUE power usage effectiveness
Formatted
...
pCEF partial cooling efficiency factor
Formatted: Font: 11 pt
Formatted: Space After: 0 pt, Line spacing: single
2 © ISO #### – All rights reserved
2 © ISO/IEC 2023 – All rights reserved
---------------------- Page: 10 ----------------------
ISO/IEC 30134-7:2023(E)
Formatted
...
Formatted
...
pPUE partial power usage effectiveness
Formatted
...

pPUE partial power usage effectiveness for heating, ventilation and air conditioning

HVAC Formatted
...
systems
SEER seasonal energy efficiency ratio
Formatted
...
UPS uninterruptible power supply
Formatted
...
3.3 Symbols
Formatted
...
For the purposes of this document, the following symbols apply.
Formatted
...
Formatted
Ecooling cooling system energy consumption (annual) in kWh
...
Formatted
E part of E that is accountedattributed to the DC in kWh ...
cooling,DC cooling
Formatted
...
E part of E that is not accountedattributed to the DC in kWh
cooling, other cooling
Formatted
...
Ecooling, room part of Ecooling that is allocated to one room of the DC in kWh
Formatted
...
E electrical energy use of the sub-system in kWh
cooling,subsystem
Formatted
...
E electrical energy transferred to heat in kWh
heat
Formatted
...
Eheat, room electrical energy allocated to one room transferred to heat in kWh
Formatted
...
E electrical energy of the DC that is transferred to heat (annual) in kWh
heat,DC
Formatted
...
EIT IT equipment energy consumption (annual) in kWh
Formatted
...
E IT equipment energy consumption (annual) allocated to one room in kWh
IT, room
Formatted
...
E electrical energy losses (annual) in kWh
losses Formatted
...

Elosses, room electrical energy losses (annual) allocated to one room in kWh Formatted

...
Formatted
E total energy consumption allocated to one room (annual) in kWh
total, room ...
Formatted
...
E total DC energy consumption (annual) in kWh
Formatted
...
FEC cooling efficiency factor
Formatted
...
F partial cooling efficiency factor
EC,p
Formatted
...
P actual electrical power of the cooling system in kW
cooling
Formatted
...
Pheat actual heat load in kW
Formatted
...
R cooling efficiency ratio
Formatted
...
RCP cooling performance ratio
Formatted
...
Formatted
...
η power usage effectiveness, PUE
U,P,p
Formatted
...
ηU,P partial power usage effectiveness, pPUE Formatted
...
Formatted
...
4 Applicable area of the data centre
Formatted
...
Formatted
...
The CER as specified in this document:
Formatted
...
© ISO #### – All rights reserved 3
© ISO/IEC 2023 – All rights reserved 3
---------------------- Page: 11 ----------------------
ISO/IEC 30134-7:2023(E)
Formatted: Space After: 36 pt, Line spacing: Exactly 12
Formatted: Font: 12 pt
— is associated with the DC infrastructure within its boundaries only;
Formatted: List Continue 1, Tab stops: 0.7 cm, Left +
1.4 cm, Left + 2.1 cm, Left + 2.8 cm, Left + 3.5 cm, Left

— describes the efficiency of a cooling system with respect to its electrical energy use.

+ 4.2 cm, Left + 4.9 cm, Left + 5.6 cm, Left + 6.3 cm,
Left + 7 cm, Left + Not at 1.25 cm

Derivatives of the CER which are useful in certain circumstances are described in Annex D.

Formatted: cite_app
Formatted: cite_app
5 Definition of the CER
Formatted: Body Text, Tab stops: Not at 1.5 cm
Formatted: Don't adjust space between Latin and Asian
The CER, R , is defined according to Formula (1):
text, Don't adjust space between Asian text and
heat
heat numbers
𝑅 = R =
𝐶𝐸 CE
cooling
cooling
Formatted:
...

INTERNATIONAL ISO/IEC
STANDARD 30134-7
First edition
Information technology — Data
centres key performance indicators —
Part 7:
Cooling efficiency ratio (CER)
PROOF/ÉPREUVE
Reference number
ISO/IEC 30134-7:2023(E)
© ISO/IEC 2023
---------------------- Page: 1 ----------------------
ISO/IEC 30134-7:2023(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2023

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
PROOF/ÉPREUVE © ISO/IEC 2023 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/IEC 30134-7:2023(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms, definitions and abbreviations ........................................................................................................................................... 1

3.1 Terms and definitions ...................................................................................................................................................................... 1

3.2 Abbreviated terms .............................................................................................................................................................................. 2

3.3 Symbols ......................................................................................................................................................................................................... 2

4 Applicable area of the data centre .................................................................................................................................................... 3

5 Definition of the CER ........................................................................................................................................................................................ 4

6 Measurement of CER ........................................................................................................................................................................................5

6.1 General ........................................................................................................................................................................................................... 5

6.2 Requirements .......................................................................................................................................................................................... 5

6.3 Recommendations ............................................................................................................................................................................... 5

7 Application of CER .............................................................................................................................................................................................. 5

8 Reporting of CER .................................................................................................................................................................................................. 6

8.1 Requirements .......................................................................................................................................................................................... 6

8.1.1 Standard construct for communicating CER ............................................................................................. 6

8.1.2 Data for public reporting of CER .......................................................................................................................... 6

8.2 Recommendations ............................................................................................................................................................................... 7

Annex A (informative) Correlation of CER and other KPIs ........................................................................................................... 8

Annex B (normative) Examples of usage of CER ...................................................................................................................................10

Annex C (informative) Parameters influencing CER .......................................................................................................................11

Annex D (normative) Derivatives of CER ........................................................................................................................................... ...........12

Bibliography .............................................................................................................................................................................................................................16

iii
© ISO/IEC 2023 – All rights reserved PROOF/ÉPREUVE
---------------------- Page: 3 ----------------------
ISO/IEC 30134-7:2023(E)
Foreword

ISO (the International Organization for Standardization) and IEC (the International Electrotechnical

Commission) form the specialized system for worldwide standardization. National bodies that are

members of ISO or IEC participate in the development of International Standards through technical

committees established by the respective organization to deal with particular fields of technical

activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international

organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the

work.

The procedures used to develop this document and those intended for its further maintenance

are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria

needed for the different types of document should be noted. This document was drafted in

accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives or

www.iec.ch/members_experts/refdocs).

Attention is drawn to the possibility that some of the elements of this document may be the subject

of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent

rights. Details of any patent rights identified during the development of the document will be in the

Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC

list of patent declarations received (see https://patents.iec.ch).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see

www.iso.org/iso/foreword.html. In the IEC, see www.iec.ch/understanding-standards.

This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,

Subcommittee SC 39, Sustainability, IT and data centres.

A list of all parts in the ISO/IEC 30134 series can be found on the ISO and IEC websites.

Any feedback or questions on this document should be directed to the user’s national standards

body. A complete listing of these bodies can be found at www.iso.org/members.html and

www.iec.ch/national-committees.
PROOF/ÉPREUVE © ISO/IEC 2023 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/IEC 30134-7:2023(E)
Introduction

The global economy is today reliant on information and communication technologies and the associated

generation, transmission, dissemination, computation and storage of digital data. All markets have

experienced exponential growth in that data, for social, educational and business sectors and, while the

internet backbone carries the traffic, there are a wide variety of data centres at nodes and hubs within

both private enterprise and shared/collocation facilities.

The historical data generation growth rate exceeds the capacity growth rate of information and

communications technology hardware and, with less than half (in 2014) of the world’s population

having access to an internet connection, that growth in data can only accelerate. In addition, with

many governments having “digital agendas” to provide both citizens and businesses with ever-faster

broadband access, the very increase in network speed and capacity will, by itself, generate ever more

usage (Jevons Paradox). Data generation and the consequential increase in data processing and storage

are directly linked to increasing power consumption.

With this background, data centre growth, and power consumption in particular, is an inevitable

consequence; this growth will demand increasing power consumption despite the most stringent

energy efficiency strategies. This makes the need for key performance indicators (KPIs) that cover

the effective use of resources (including but not limited to energy) and the reduction of CO emissions

essential.

Within the ISO/IEC 30134 series, the term “resource usage effectiveness” is more generally used for

KPIs in preference to “resource usage efficiency”, which is restricted to situations where the input and

output parameters used to define the KPI have the same units.

The cooling efficiency ratio (CER) allows data centre operators to quickly determine the efficiency of

their data centre cooling system, compare the results, and determine if energy efficiency improvements

need to be made. The impact of operational cooling efficiency is proving to be extremely important in

the design, location and operation of current and future data centres.

In order to determine the overall resource efficiency of a data centre, a holistic suite of metrics

is required. This document is one of a series of International Standards for such KPIs and has been

produced in accordance with ISO/IEC 30134-1, which defines common requirements for a holistic suite

of KPIs for data centre resource efficiency. This document does not specify limits or targets for the KPI

and does not describe or imply, unless specifically stated, any form of aggregation of this KPI into a

combination with other KPIs for data centre resource efficiency. This document presents specific rules

on CER’s use, along with its theoretical and mathematical development. This document concludes with

several examples of site concepts that could employ the CER metric.
© ISO/IEC 2023 – All rights reserved PROOF/ÉPREUVE
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO/IEC 30134-7:2023(E)
Information technology — Data centres key performance
indicators —
Part 7:
Cooling efficiency ratio (CER)
1 Scope

This document specifies the cooling efficiency ratio (CER) as a key performance indicator (KPI) for

quantifying the efficient use of energy to control the temperature of spaces within a data centre (DC).

This document:
a) defines the CER of a DC;

b) describes the relationship of this KPI to a DC’s infrastructure, information technology equipment

and information technology operations;

c) defines the measurement, the calculation and the reporting of the parameter; and

d) provides information on the correct interpretation of the CER.
Annex A describes the correlation of the CER and other KPIs.
Annex B provides examples of the usage of the CER.
Annex C introduces the parameters that affect the CER.

Annex D describes requirements and recommendations for derivatives of KPIs associated with the CER.

This document is not applicable to cooling systems that are not powered by electricity (e.g. heat-driven

absorption chillers).
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO/IEC 30134-1, Information technology — Data centres — Key performance indicators — Part 1:

Overview and general requirements
3 Terms, definitions and abbreviations
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO/IEC 30134-1 and the following

apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
© ISO/IEC 2023 – All rights reserved PROOF/ÉPREUVE
---------------------- Page: 6 ----------------------
ISO/IEC 30134-7:2023(E)
3.1.1
cooling efficiency ratio
CER
ratio of total heat removed and electrical energy used by a cooling system

Note 1 to entry: The value of "total heat annual removed" from the DC is measured in kWh.

3.1.2
cooling performance ratio
CPR
ratio of actual heat load and electrical power used by a cooling system
Note 1 to entry: The actual heat load is measured in kW.
3.1.3
energy loss
dissipation of energy caused by electric utilities
Note 1 to entry: The energy loss turned into heat are measured in kWh.

Note 2 to entry: Energy loss is caused, for example. by transformers, uninterruptible power supply (UPS), fans of

computer room air handling units (CRAH), pumps, lighting, power cables.
3.2 Abbreviated terms

For the purposes of this document, the terms and definitions given in ISO/IEC 30134-1 and the following

apply.
CEF cooling efficiency factor
CER cooling efficiency ratio
COP coefficient of performance
CPR cooling performance ratio
DC data centre
EER energy efficiency ratio
HVAC heating, ventilation, air conditioning
iCER interim cooling efficiency ratio
NSenCOP net sensible coefficient of performance
PUE power usage effectiveness
pCEF partial cooling efficiency factor
pPUE partial power usage effectiveness

pPUE partial power usage effectiveness for heating, ventilation and air conditioning systems

HVAC
SEER seasonal energy efficiency ratio
UPS uninterruptible power supply
3.3 Symbols
For the purposes of this document, the following symbols apply.
PROOF/ÉPREUVE © ISO/IEC 2023 – All rights reserved
---------------------- Page: 7 ----------------------
ISO/IEC 30134-7:2023(E)
E cooling system energy consumption (annual) in kWh
cooling
E part of E that is attributed to the DC in kWh
cooling,DC cooling
E part of E that is not attributed to the DC in kWh
cooling,other cooling
E part of E that is allocated to one room of the DC in kWh
cooling,room cooling
E electrical energy use of the sub-system in kWh
cooling,subsystem
E electrical energy transferred to heat in kWh
heat
E electrical energy allocated to one room transferred to heat in kWh
heat,room
E electrical energy of the DC that is transferred to heat (annual) in kWh
heat,DC
E IT equipment energy consumption (annual) in kWh
E IT equipment energy consumption (annual) allocated to one room in kWh
IT,room
E electrical energy losses (annual) in kWh
losses
E electrical energy losses (annual) allocated to one room in kWh
losses,room
E total energy consumption allocated to one room (annual) in kWh
total,room
E total DC energy consumption (annual) in kWh
F cooling efficiency factor
F partial cooling efficiency factor
EC,p
P actual electrical power of the cooling system in kW
cooling
P actual heat load in kW
heat
R cooling efficiency ratio
R cooling performance ratio
η power usage effectiveness, PUE
U,P,p
η partial power usage effectiveness, pPUE
U,P
4 Applicable area of the data centre
The CER as specified in this document:
— is associated with the DC infrastructure within its boundaries only;

— describes the efficiency of a cooling system with respect to its electrical energy use.

Derivatives of the CER which are useful in certain circumstances are described in Annex D.

© ISO/IEC 2023 – All rights reserved PROOF/ÉPREUVE
---------------------- Page: 8 ----------------------
ISO/IEC 30134-7:2023(E)
5 Definition of the CER
The CER, R , is defined according to Formula (1):
heat
R = (1)
cooling
Both E and E shall be measured in kWh and for the same time period.
heat cooling

NOTE Within ISO/IEC TS 22237-7:2018, Formula (1) is designated as the energy efficiency ratio (EER). This

will be corrected with the revision of ISO/IEC TS 22237-7.
The following applies to dedicated DC infrastructures:
E = E
heat heat,DC
E = E
cooling cooling,DC

Figure 1 shows the relationship between the different energy forms for dedicated DC infrastructures.

where
E = E + E + E
DC IT losses cooling, DC
Figure 1 — Dedicated cooling system

The calculation of the heat load of the DC is based on the assumption that all electrical energy used in

the DC is transferred to heat:
E = E + E
heat,DC IT losses
E shall be measured in accordance with ISO/IEC 30134-2.

If available, E shall include all other electrical losses, e.g. electrical energy of UPS, energy storage,

losses

transformers, power cables or lighting transferred to heat within the DC boundaries.

For shared cooling systems in multi-purpose buildings, which include a DC, the energy consumption of

the cooling system is determined from the energy consumption from the shared cooling system.

Figure 2 shows the relationship between the different energy forms for shared cooling systems in

multi-purpose buildings including a DC.
PROOF/ÉPREUVE © ISO/IEC 2023 – All rights reserved
---------------------- Page: 9 ----------------------
ISO/IEC 30134-7:2023(E)
Where

cooling,DC is the part of the energy use for the entire shared cooling system to remove the DC related heat loads;

cooling,other is the part of the energy use for the entire shared cooling system to remove non-DC related heat loads.

Figure 2 — Shared cooling system
6 Measurement of CER
6.1 General

The calculation of CER requires the recording and documenting of total heat removed and electrical

energy used for cooling over a coincident period of 12 months. This document does not specify the

frequency of measurements of total heat removed and electrical energy used for cooling, since CER is

calculated on an annual timeframe. However, the frequency of measurement employed will define the

timing of subsequent CER calculations on a rolling annual basis.
6.2 Requirements

The measurement of CER requires the measurement of the total heat removed and the electrical energy

used in the same period.

In order to measure the heat removed, the volume of the coolant and its heat capacity shall be measured.

In cases like direct free cooling, every parameter influencing the heat capacity (like humidity) shall be

measured for an acceptable accuracy of the calculation of the heat removed. In case of redundant pipes,

every pipe shall be measured.

For the electrical energy use all components of the cooling infrastructure (like pumps) valves etc., shall

be measured and included in the energy used. Electrical metering shall be based on kWh, not on power

in kW. In the case of energy reuse, the energy consumption of additional systems for distributing the

reused heat in the building shall not be part of the electrical energy consumption. Annex B shall apply.

In cases where it is necessary to describe versions of the CER for measurement periods of less than 12

months or for DC subsystems, the measurements described in Annex D shall be used.

6.3 Recommendations

DCs should implement meters with remote reading and data history storage capabilities.

7 Application of CER

CER can be used by DC managers to report the efficiency of the cooling system used to control the

temperature of the spaces within the DC. This KPI can be used independently, but to achieve a more

holistic picture of the resource efficiency of the DC, other KPIs described in the ISO/IEC 30134 series

should be considered. When using CER, the PUE in particular should be considered. Where CER is

reported, the corresponding PUE value should also be reported.
© ISO/IEC 2023 – All rights reserved PROOF/ÉPREUVE
---------------------- Page: 10 ----------------------
ISO/IEC 30134-7:2023(E)
8 Reporting of CER
8.1 Requirements
8.1.1 Standard construct for communicating CER

For a reported CER to be meaningful, the reporting organization shall provide the following information:

a) the DC under inspection;
b) the CER value [or cooling performance ratio (CPR) value; see D.4];

c) the termination date of the period of measurement using the format of ISO 8601-1 (e.g. yyyy-mm-

dd).
8.1.2 Data for public reporting of CER
8.1.2.1 Required information
The following data shall be provided when publicly reporting CER data:
a) contact information;

NOTE 1 Only the organization’s name or contact are recommended to be displayed in public inquiries.

b) DC location information (address, county or region);

NOTE 2 Only state or local region information is required to be displayed in public inquiries.

c) measurement results: CER with appropriate nomenclature;

d) use case: dedicated DC infrastructures or shared cooling systems in multi-purpose buildings

including a DC.
8.1.2.2 Required supporting evidence

Information on the DC which shall be available upon request as a minimum includes:

a) organization’s name, contact information and regional environmental description;

b) measurement results: CER with appropriate nomenclature;
c) measurement(s) start dates and assessment completion dates;
d) E value;

e) report on the size of the computer room, telecom room and control room spaces;

f) external environmental conditions consisting of minimum, maximum and average temperature,

humidity and altitude;
g) corresponding PUE value and category.

NOTE The IEC 62052 series and the IEC 62053 series provide a reference for the measurement of electrical

energy.
8.1.2.3 Example of reporting CER values

Using the construct of 8.1.1, examples of specific CER designations and their interpretation are given as

follows.
PROOF/ÉPREUVE © ISO/IEC 2023 – All rights reserved
---------------------- Page: 11 ----------------------
ISO/IEC 30134-7:2023(E)
Sample CER designation:
DC X: CER (2018-12-31) = 3,5
Interpretation: In the year 2018 the CER value of DC X was 3,5.
8.2 Recommendations

The following information can potentially be useful in tracking the CER trends within a DC:

a) DC size (facility m );
b) total DC design load for the facility (e.g. 10 MW);
c) name of the possible auditor and method used for auditing;
d) DC contact information;
e) DC environmental conditions;
f) DC location and region;
g) DC’s mission;
h) DC archetype percentages (e.g. 20 % web hosting, 80 % email);
i) DC commissioned date;
j) numbers of servers, routers, and storage devices;
k) average and peak server CPU utilization;
l) percentage of servers using virtualization;
m) average age of IT equipment by type;

n) average age of facility equipment by type (cooling and power distribution equipment);

o) DC availability objectives (see ISO/IEC 30134-1:2015, Annex A);
p) cooling and air-handling details.

NOTE Other KPIs within the ISO/IEC 30134 series can assist in the recording of the above information.

In general, the CER should be reported to one decimal place. However, depending on the accuracy of

both measurements, the heat removed and the electrical usage, more than one decimal place may be

reported.

Reporting of CER for external communication should be accompanied by additional cooling conditions,

like usage of direct free cooling or water. Where KPIs exist for these conditions, they should be

determined and reported together with the CER.

For usage in energy management and verification of measures of improvement, a report of interim

cooling efficiency ratio (iCER; see D.1) can be plotted against the outside air temperature and humidity,

if applicable. As there is a strong dependency of the iCER from outside air temperature and other

conditions like humidity for most energy efficient cooling systems, every improvement can be detected

in a shift of the iCER value at the same outside air temperature.
© ISO/IEC 2023 – All rights reserved PROOF/ÉPREUVE
---------------------- Page: 12 ----------------------
ISO/IEC 30134-7:2023(E)
Annex A
(informative)
Correlation of CER and other KPIs
A.1 General

Cooling is one of the most important aspects of energy use in a DC, and one with the largest potential

for optimization of energy efficiency. The partial PUE (pPUE) of the cooling infrastructure provides

insight into that potential in comparison to the other parts of the infrastructure, but it is less helpful in

energy management to verify the effect of improvements of the cooling infrastructure, as the value of a

pPUE in general is between 1 and the PUE of the DC, as shown in Formula (A.1):
1 < η < η (A.1)
U,P,p U,P
where
η is the power usage effectiveness, PUE;
U,P,p
η is the partial power usage effectiveness, pPUE;
U,P

See ISO/IEC 30134-2 for the definition and further information on the usage of PUE and pPUE.

Measuring the heat removed divided by the electrical energy used by the cooling infrastructure

provides a much more sensitive KPI.
A.2 Discussion of existing terms for performance rating

There are already multiple terms defined for performance rating of machines (e.g. heat pumps and

cooling equipment) as one part of the entire cooling system, e.g. in Reference [6] and Reference [10]; see

Table A.1. All terms in Table A.1 only deal with machine characteristics, defined under fixed conditions.

There is currently no term of efficiency for the entire cooling system based on real life measurements

during DC operation. CER and CPR close this gap: both are based on measurements under real conditions

in DC operation. CPR refers to COP and CER refers to SEER.
Table A.1 — Terms of efficiency of cooling machines
Term Abbreviated term Infrastructure Comments
Coefficient of performance COP Heat pumps Machine characteristic,
defined under fixed condi-
tions
Energy efficiency ratio EER Cooling machines Machine characteristic,
defined under fixed condi-
tions
Seasonal EER SEER Cooling machines Defined for the period of
one year

Net Sensible Coefficient of NSenCOP Computer room air condi- Includes allowances for

Performance tioners outdoor heat rejection fans
and fluid pumps

The coefficient of performance (COP) is a value based on actual heat load and electrical power. It

describes the performance under controlled, optimal conditions, thus giving a maximum value for

PROOF/ÉPREUVE © ISO/IEC 2023 – All rights reserved
---------------------- Page: 13 ----------------------
ISO/IEC 30134-7:2023(E)

performance, not a realistic one for operation in a real DC. Furthermore, it is defined for heat pumps,

not for cooling infrastructure.

According to References [6] and [10], the EER is a ratio of the cooling capacity to the power input value

at any given set of rating conditions. It also describes the performance under controlled conditions, but

it already acknowledges the influence of part load operation of a cooling infrastructure.

According to Reference [6], the SEER is the total heat removed from the conditioned space during

the annual cooling season divided by the total electrical energy consumed by the air conditioner or

heat pump during the same season. It describes the performance of a cooling infrastructure under

real conditions based on a period of a full year. It therefore accounts for the dependency of the EER on

climate conditions, or, to be more precise, on the outside air temperature.
© ISO/IEC 2023 – All rights reserved PROOF/ÉPREUVE
---------------------- Page: 14 ----------------------
ISO/IEC 30134-7:2023(E)
Annex B
(normative)
Examples of usage of CER
B.1 Determining PUE in data centres with different computer rooms using CER

Operators of DCs with multiple rooms that have different characteristics (e.g. in energy density of the

racks or air flow strategies) can wish to compare the energy efficiency of these rooms. The calculation

of a PUE value for each room (pPUE) can be a challenge when infrastructure is shared within the DC.

On the power trail, this issue can be solved by an appropriate set of sub-meters providing the ability to

account for IT energy and the electrical energy losses (e.g. from UPS, energy storage, etc.).

Accounting for the usage of electrical energy for a central cooling infrastructure requires the calculation

of the heat load of every room using Formula (B.1):
E = E + E (B.1)
heat,room IT,room losses,room
The total energy used by each room can be calculated b
...