ISO/IEC 30134-7:2023
(Main)Information technology — Data centres key performance indicators — Part 7: Cooling efficiency ratio (CER)
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).
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INTERNATIONAL ISO/IEC
STANDARD 30134-7
First edition
2023-03
Information technology — Data
centres key performance indicators —
Part 7:
Cooling efficiency ratio (CER)
Reference number
ISO/IEC 30134-7:2023(E)
© ISO/IEC 2023
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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
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Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
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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
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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.
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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
2
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.
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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/
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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.
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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
IT
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
DC
F cooling efficiency factor
EC
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
CE
R cooling performance ratio
CP
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.
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ISO/IEC 30134-7:2023(E)
5 Definition of the CER
The CER, R , is defined according to Formula (1):
CE
E
heat
R = (1)
CE
E
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.
IT
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.
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ISO/IEC 30134-7:2023(E)
Where
E
cooling,DC is the part of the energy use for the entire shared cooling system to remove the DC related heat loads;
E
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.
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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;
IT
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.
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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:
2
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.
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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
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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.
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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 based on the CER of the cooling infrastructure
and the value of E for each room, as shown in Formula (B.2):
heat
EE=+EE+=
total,room IT,room losses,room cooling,room
(B.2)
1
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ISO/IEC DIS 30134-7:20222023(E)
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Contents
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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
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D.4.1 Calculation of CPR . 12
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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
pt
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
DC
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
CE
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
pt
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):
CE
text, Don't adjust space between Asian text and
E
𝐸
heat
heat numbers
𝑅 = R =
𝐶𝐸 CE
𝐸
cooling
E
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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
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.
iv
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
2
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.
v
© 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/
1
© 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.
2
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
IT
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
DC
F cooling efficiency factor
EC
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
CE
R cooling performance ratio
CP
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.
3
© 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):
CE
E
heat
R = (1)
CE
E
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.
IT
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.
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ISO/IEC 30134-7:2023(E)
Where
E
cooling,DC is the part of the energy use for the entire shared cooling system to remove the DC related heat loads;
E
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.
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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;
IT
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.
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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:
2
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.
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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
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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.
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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
...
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