Information technology — Data centres key performance indicators — Part 9: Water usage effectiveness (WUE)

This document specifies water usage effectiveness (WUE) as a key performance indicator (KPI) for quantifying the water consumption of a data centre during the use phase of the data centre life cycle. WUE is a simple method for reporting the water intensity of the data centre operating. By reporting water consumption, it is possible to present the data centre's resource effectiveness. This document: a) defines the WUE of a data centre; b) introduces WUE measurement categories; c) describes the relationship of this KPI to a data centre’s infrastructure, information technology equipment and information technology operations; d) defines the measurement, the calculation and the reporting of the parameter; and e) provides information on the correct interpretation of the WUE.

Technologies de l'information — Indicateurs de performance clés des centres de données — Partie 9: Efficacité dans l'utilisation de l'eau (WUE)

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Published
Publication Date
23-Mar-2022
Current Stage
5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
Start Date
02-Dec-2021
Completion Date
02-Dec-2021
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INTERNATIONAL ISO/IEC
STANDARD 30134-9
First edition
2022-03
Information technology — Data
centres key performance indicators —
Part 9:
Water usage effectiveness (WUE)
Technologies de l'information — Indicateurs de performance clés des
centres de données —
Partie 9: Efficacité dans l'utilisation de l'eau (WUE)
Reference number
ISO/IEC 30134-9:2022(E)
© ISO/IEC 2022
---------------------- Page: 1 ----------------------
ISO/IEC 30134-9:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2022

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
© ISO/IEC 2022 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/IEC 30134-9:2022(E)
Contents Page

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

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

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

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

3 Terms, definitions, abbreviated terms and symbols .................................................................................................... 1

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

3.2 Abbreviated terms .............................................................................................................................................................................. 3

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

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

5 Determination of WUE ...................................................................................................................................................................................5

6 Measurement of WUE ........................................................................................................................................... ...........................................5

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

6.2 Measuring actual water usage.................................................................................................................................................. 5

6.2.1 Calculation, measurement period and frequency ................................................................................. 5

6.2.2 Categories of WUE ............................................................................................................................................................ 5

7 Application of WUE ............................................................................................................................................................................................8

8 Reporting of WUE ................................................................................................................................................................................................ 8

8.1 Requirements .......................................................................................................................................................................................... 8

8.1.1 Standard construct for communicating WUE data ............................................................................. 8

8.1.2 Data for public reporting of WUE ........................................................................................................................ 9

8.2 Recommendations ............................................................................................................................................................................... 9

8.3 Example of reporting WUE values ..................................................................................................................................... 10

8.4 WUE derivatives ................................................................................................................................................................................ 10

8.4.1 Purpose of WUE derivatives ................................................................................................................................. 10

8.4.2 Interim WUE ....................................................................................................................................................................... 11

8.4.3 Partial WUE ......................................................................................................................................................................... 11

8.4.4 Design WUE ......................................................................................................................................................................... 11

8.4.5 Quality WUE ........................................................................................................................................................................ 11

8.4.6 Peak WUE ..............................................................................................................................................................................12

8.5 Water reuse factor (WRF) ......................................................................................................................................................... 12

Annex A (informative) Examples of use ........................................................................................................................................................13

Annex B (normative) Water siginficance .....................................................................................................................................................15

Annex C (informative) Energy water intensity factor ....................................................................................................................16

Annex D (normative) Land consumption .....................................................................................................................................................17

Bibliography .............................................................................................................................................................................................................................19

iii
© ISO/IEC 2022 – All rights reserved
---------------------- Page: 3 ----------------------
ISO/IEC 30134-9:2022(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.
© ISO/IEC 2022 – All rights reserved
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ISO/IEC 30134-9:2022(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. 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 water) 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.

Water usage effectiveness (WUE) is intended to support data centre practitioners in obtaining an in

depth understanding of the performance of the data centre’s cooling installation in comparison with

similar systems, thereby creating a tool for improvning the sustainability of the data centre. The

impact of operational water usage is emerging as being 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 WUE’s use, along with its theoretical and mathematical development. This document concludes with

several examples of site concepts that could employ the WUE metric.
© ISO/IEC 2022 – All rights reserved
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INTERNATIONAL STANDARD ISO/IEC 30134-9:2022(E)
Information technology — Data centres key performance
indicators —
Part 9:
Water usage effectiveness (WUE)
1 Scope

This document specifies water usage effectiveness (WUE) as a key performance indicator (KPI) for

quantifying the water consumption of a data centre during the use phase of the data centre life cycle.

WUE is a simple method for reporting the water intensity of the data centre operating. By reporting

water consumption, it is possible to present the data centre's resource effectiveness.

This document:
a) defines the WUE of a data centre;
b) introduces WUE measurement categories;

c) describes the relationship of this KPI to a data centre’s infrastructure, information technology

equipment and information technology operations;

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

e) provides information on the correct interpretation of the WUE.
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

ISO 8601-1, Date and time — Representations for information interchange — Part 1: Basic rules

3 Terms, definitions, abbreviated terms and symbols
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 2022 – All rights reserved
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ISO/IEC 30134-9:2022(E)
3.1.1
total data centre energy consumption

total annual energy consumption for all energy types serving the data centre at its boundary

Note 1 to entry: The total data centre energy is measured in MWh; the energy is measured with energy metering

devices at the boundary of the data centre or points of generation within the boundary.

Note 2 to entry: This includes electricity, natural gas, hydrogen, bioethanol and district utilities such as supplied

chilled water or condenser water.
Note 3 to entry: Total annual energy includes supporting infrastructure.
[SOURCE: ISO/IEC 30134-2:2016, 3.1.7, modified.]
3.1.2
IT equipment energy consumption

energy consumed by equipment that is used to manage, process, store or route data within the compute

space

Note 1 to entry: IT equipment energy consumption is measured in MWh; examples for IT equipment are servers,

storage equipment, and telecommunications equipment.

Note 2 to entry: IT equipment energy use follows the same categories as in ISO 30134-2 Power usage effectiveness.

[SOURCE: ISO/IEC 30134-2:2016, 3.1.1, modified.]
3.1.3
water usage effectiveness

ratio of the data centre water consumption divided by the energy consumed by IT equipment

3.1.4
water use
water that is used by end-users for a specific purpose within a given territory

Note 1 to entry: For the purposes of this document, water use corresponds to the water consumption caused by

the processing of data in a data centre.

Note 2 to entry: Domestic use, irrigation or industrial processing are examples of a given territory.

Note 3 to entry: Water use is measured in water volume (m ) consumed.
3.1.5
reused water

water that is leaving the data centre boundaries for an alternative non-data-centre use

Note 1 to entry: The non-data-centre use of water is usually defined by local regulations for reuse.

3.1.6
potable water

water that is free from contamination and that is safe to drink or to use for food and beverage

preparation and personal hygiene
Note 1 to entry: Potable water is also known as drinking water.

Note 2 to entry: The definition of the quality criteria of potable water is usually subject to national or local

regulations; if there is no information about the criteria see Reference [2].
3.1.7
energy water intensity factor
amount of water that is used to produce energy
Note 1 to entry: Energy water intensity factor is measured in m per MWh.
© ISO/IEC 2022 – All rights reserved
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ISO/IEC 30134-9:2022(E)
3.1.8
water significance
amount of renewable freshwater that is available for each person each year

Note 1 to entry: Within the approach of this document, water significance is categorized by different levels of

water stress.
3.1.9
water stress
ability to meet human and ecological demand for freshwater
3.1.10
water quality

physical, chemical and biological characteristics of water concerning its suitability for an intended use

by humans, ecosystems or industrial processes
3.1.11
land consumption

loss of water permeability of the soil intended for use by humans, ecosystems or industrial processes

3.2 Abbreviated terms

For the purposes of this document, the abbreviated terms in ISO/IEC 30134-1 and the following apply.

DC data centre
dWUE design water usage effectiveness
EWIF energy water intensity factor
FI falkenmark indicator
iWUE interim water usage effectiveness
peakWUE peak water usage effectiveness
PUE power usage effectiveness
pWUE partial water usage effectiveness
qWUE quality water usage effectiveness
WRF water reuse factor
WUE water usage effectiveness
3.3 Symbols
For the purposes of this document the following symbols apply:
E total data centre energy consumption (annual) in MWh
E IT equipment energy consumption (annual) in MWh
f energy water intensity factor (EWIF)
EWI
f water reuse factor (WRF)
r,w
f drainage factor of fully sealed surfaces
s(F)
© ISO/IEC 2022 – All rights reserved
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ISO/IEC 30134-9:2022(E)
f drainage factor of few sealed surfaces
s(f)
f drainage factor of heavily sealed surfaces
s(h)

I total water input from outside the data centre boundaries (annual) measured by total vol-

ume in m
I water input from water consumption of energy production
w,e
I water input from potable water
w,p
I water input from rainwater
w,rw
i falkenmark indicator (FI)
L data centre land consumption

O total water returned out of the data centre boundaries (annual) measured by total volume

in m
p population
s fully sealed surface
s few sealed surfaces
s heavily sealed surfaces
s surface runoff (annual) measured in m
run
U water usage of the data centre (annual) measured by total volume in m
U water reusage of the data centre (annual) measured by total volume in m
r,w
U industrial water reuse
r,w,I
U non-industrial water reuse
r,w,NI
η water usage effectiveness
U,W
η interim water usage effectiveness
U,W,i
NOTE Unlike for PUE, the unit of the energy used in WUE is MWh.
4 Applicable area of the data centre
WUE as specified in this document:

— is associated with the data centre infrastructure and IT equipment within its boundaries only;

— describes the water usage in relation to facilities with given environmental conditions, IT load

characteristics, availability requirements, maintenance and security requirements;

— measures the relationship between the total data centre water usage and the IT equipment energy

consumed.
WUE does not:

— account for efficiency of other resources such as human resources, space or CO ;

— provide a data centre productivity metric;
© ISO/IEC 2022 – All rights reserved
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ISO/IEC 30134-9:2022(E)
— provide a standalone, comprehensive efficiency metric;

— account for quality of the water reuse process outside the data centre boundaries;

— account for water down- or upgrade (reducing or improving water quality).
5 Determination of WUE

WUE provides a way to determine the water usage associated with data centres. A value of 0,0 indicates

that no water use is associated with the data centre‘s operations. WUE has no theoretical upper and no

theoretical lower boundary.
WUE is defined according to Formula (1):
η =
U,W
(1)
Annual water usage is calculated according to Formula (2) as:
U = I − O (2)
w w w

WUE may be applied in mixed-use buildings when measurement of the difference between water used

for the data centre and that for other functions is possible.
6 Measurement of WUE
6.1 General

All KPIs of the ISO/IEC 30134 series are defined within the boundaries of a data centre (see

ISO/IEC 30134-1).
6.2 Measuring actual water usage
6.2.1 Calculation, measurement period and frequency

The minimum calculation and measurement period requires twelve months of cumulative energy

and water values. Annualized data used to calculate WUE shall be documented. The annual energy

values for energy consumption of the IT equipment collected shall cover the same time period. It is not

necessary to define the frequency of measurement or assessments for the annual WUE determination,

as the annual water value is a continuous integration of energy consumed in that timeframe. Examples

of the calculation are shown in the Annex A.

NOTE The measurement or assessment frequency can be necessary for subsystem improvements (refer to

partial PUE), but is not required for WUE disclosures.
6.2.2 Categories of WUE
6.2.2.1 Introduction

The categories of WUE are defined, as shown in Table 1, to provide a defined route to refine the accuracy

of the WUE measured. WUE considers different water qualities and types of reused water. Category 3

requires additional reporting for regional water significance (level of water stress, in accordance with

Annex B) and land consumption (in accordance with Annex D).
© ISO/IEC 2022 – All rights reserved
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ISO/IEC 30134-9:2022(E)
Table 1 — WUE categories
Source Category 1 (WUE ) Category 2 (WUE ) Category 3 (WUE )
1 2 3
basic intermediate advanced

Considered water Physical water input of the Physical water input of the Water consumption of energy

input DC. DC. production and physical water
input excluding rainwater.

Considered water No water reuse; water input Water output of the DC for Water output of the DC with

output equates to water use. non-industrial reuse. measurement of non-industrial
and industrial reuse.
Additional report- No. No. Regional water stress level and
ing land consumption.

The water qualities for the water input are differentiated into potable and non-potable water. If there

exists a regional definition of water qualities for potable and non-potable, this shall be taken into

account. Otherwise definitions given in this document shall be applied. For water output, a distinction

is made between two typs of reused water: non-industrial reuse and industrial reuse. The definition

of the criteria for water reuse is usually subject to national or local regulation. The part of the water

output that is not reused is specified as used water.
6.2.2.2 WUE category 1: water usage without reuse

WUE is a metric considering total water consumption of the data centre. For the water output there is

no distinction of water use and water reuse in category 1 (see Figure 1). For WUE the significance of

regional water shortage and land consumption is not considered.
NOTE For the water input, potable water and non-potable water are considered.

WUE includes the water used at the DC location for operation of the data centre. This contains water

used for humidification and water evaporated on site for energy production or cooling of the data

centre and its support systems.
Figure 1 — WUE category 1
The WUE for category 1 is calculated using Formula (3):
η = (3)
U,W,1

For category 1, I is equal to U . For the water output in category 1 there is no reuse of water considered.

w w

This means that all the water that goes into the DC is leaving the DC as used water. WUE requires only

basic measurements for the water input. Measurements for the water output are not necessary. For

WUE an additional reporting of regional water stress level and land consumption is not necessary.

6.2.2.3 WUE category 2: water usage including reuse

WUE is a metric considering total water consumption of the data centre. For the water output there

is a distinction of water use and water reuse in category 2 (see Figure 2). For category 2, the reuse of

© ISO/IEC 2022 – All rights reserved
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ISO/IEC 30134-9:2022(E)

water refers exclusively to non-industrial water. For WUE an additional reporting of regional water

stress level and land consumption is not necessary.
Figure 2 — WUE category 2
The WUE for category 2 is calculated using Formula (4):
η = (4)
U,W,2
where U = I − U
w w r,w,I

WUE requires only basic measurements for the water input. The non-industrial water reuse shall be

measured. For WUE an additional reporting of regional water stress level and land consumption is not

necessary.
6.2.2.4 WUE category 3: water usage including energy and industrial reuse

WUE is a metric considering total water consumption of the data centre. For category 3, the water

input excluding used rainwater for DC operations shall be determined. In addition, water consumption

of energy production that is used by the data centre shall be determined (see Figure 3).

NOTE 1 By excluding rainwater from the water input, benefits for the use of collected water from rain are

considered. Used rainwater is part of the non-potable water input.

To determine the water consumption of energy production that is used by the data centre, the total

energy consumption of the data centre needs to be known. This value shall then be combined with an

EWIF (see Annex C) that is based on the water used to produce the energy. The data for the EWIF shall

be provided by the energy provider/producer.

If the actual energy water intensity values are not available from the local energy supplier, WUE

calculations are limited to the WUE and WUE methods. The EWIF values in Table C.1 are examples

1 2

and shall not be used in the absence of actual values from the local energy supplier.

NOTE 2 For used water in the delivery of the energy (e.g. electricity, heat, cold, natural gas, diesel fuel) there is

no physical water input at the data centre boundary. Water input for energy is always "used“ because electricity

is "lost“ (converted into heat).

For the water output there is a distinction of water use and water reuse in category 3. For category 3,

the reuse of water refers to non-industrial water and industrial water.

The reporting WUE considers the significance of regional water shortage and land consumption.

© ISO/IEC 2022 – All rights reserved
---------------------- Page: 12 ----------------------
ISO/IEC 30134-9:2022(E)
Figure 3 — WUE category 3
The WUE for category 3 is calculated using Formula (4):
η = (5)
U,W,3
where U = (I − I + I ) − (U + U )
w w w,rw w,e r,w,I r,w,IN
and where I = E × f
w,e DC EWI
7 Application of WUE

WUE can be used by data centre managers to monitor and report water consumption related to IT

energy consumption in the data centre.

This KPI can be used independently, but to obtain a more holistic picture of the resource effectiveness of

the data centre, other KPIs of the ISO/IEC 30134 series should be considered. Where WUE is reported,

the corresponding PUE value should also be reported.

In many regions of the world, water shortage is a serious problem. Water stress causes deterioration

of freshwater resources in terms of quantity and quality. Water stress as a result of consumption is

caused by the extensive use of water in industry and agriculture/livestock breeding. A large part of this

is indirect use in water-intensive industrial processes including data centres. For that reason, category

3 considers different stages of water significance.
The expansion of built-up areas reduces o
...

FINAL
INTERNATIONAL ISO/IEC
DRAFT
STANDARD FDIS
30134-9
ISO/IEC JTC 1/SC 39
Information technology — Data
Secretariat: ANSI
centres key performance indicators —
Voting begins on:
2021-12-02
Part 9:
Voting terminates on:
Water usage effectiveness (WUE)
2022-01-27
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 SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/IEC FDIS 30134-9:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © ISO/IEC 2021
---------------------- Page: 1 ----------------------
ISO/IEC FDIS 30134-9:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2021

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
© ISO/IEC 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/IEC FDIS 30134-9:2021(E)
Contents Page

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

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

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

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

3 Terms, definitions, abbreviated terms and symbols .................................................................................................... 1

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

3.2 Abbreviated terms .............................................................................................................................................................................. 3

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

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

5 Determination of WUE ...................................................................................................................................................................................5

6 Measurement of WUE ........................................................................................................................................... ...........................................5

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

6.2 Measuring actual water usage.................................................................................................................................................. 5

6.2.1 Calculation, measurement period and frequency ................................................................................. 5

6.2.2 Categories of WUE ............................................................................................................................................................ 6

7 Application of WUE ............................................................................................................................................................................................8

8 Reporting of WUE ................................................................................................................................................................................................ 9

8.1 Requirements .......................................................................................................................................................................................... 9

8.1.1 Standard construct for communicating WUE data ............................................................................. 9

8.1.2 Data for public reporting of WUE ........................................................................................................................ 9

8.2 Recommendations ............................................................................................................................................................................ 10

8.3 Example of reporting WUE values ..................................................................................................................................... 10

8.4 WUE derivatives ................................................................................................................................................................................ 11

8.4.1 Purpose of WUE derivatives ................................................................................................................................. 11

8.4.2 Interim WUE ....................................................................................................................................................................... 11

8.4.3 Partial WUE ......................................................................................................................................................................... 11

8.4.4 Design WUE ......................................................................................................................................................................... 11

8.4.5 Quality WUE ........................................................................................................................................................................12

8.4.6 Peak WUE ..............................................................................................................................................................................12

8.5 Water reuse factor (WRF) ......................................................................................................................................................... 12

Annex A (informative) Examples of use ........................................................................................................................................................13

Annex B (normative) Water siginficance .....................................................................................................................................................15

Annex C (informative) Energy water intensity factor ....................................................................................................................16

Annex D (normative) Land consumption .....................................................................................................................................................17

Bibliography .............................................................................................................................................................................................................................19

iii
© ISO/IEC 2021 – All rights reserved
---------------------- Page: 3 ----------------------
ISO/IEC FDIS 30134-9:2021(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 FDIS 30134-9:2021(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. 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 water) 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.

Water Usage Effectiveness (WUE) will support the practitioner in obtaining an in depth understanding

of the performance of the data centre’s cooling installation in comparison with similar systems, thereby

creating a tool to improve the sustainability of the data centre. The impact of operational water usage is

emerging as being 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 WUE’s use, along with its theoretical and mathematical development. This document concludes with

several examples of site concepts that could employ the WUE metric.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/IEC FDIS 30134-9:2021(E)
Information technology — Data centres key performance
indicators —
Part 9:
Water usage effectiveness (WUE)
1 Scope

This document specifies water usage effectiveness (WUE) as a KPI for quantifying the water

consumption of a data centre during the use phase of the data centre life cycle.

WUE is a simple method for reporting the water intensity of the data centre operating. By reporting

water consumption, it is possible to present the data centre's resource effectiveness.

This document:
a) defines the WUE of a data centre,
b) introduces WUE measurement categories,

c) describes the relationship of this KPI to a data centre’s infrastructure, information technology

equipment and information technology operations,

d) defines the measurement, the calculation and the reporting of the parameter, and

e) provides information on the correct interpretation of the WUE.
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

ISO 8601-1, Date and time — Representations for information interchange — Part 1: Basic rules

3 Terms, definitions, abbreviated terms and symbols
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 FDIS 30134-9:2021(E)
3.1.1
total data centre energy consumption

total annual energy consumption for all energy types serving the data centre at its boundary

Note 1 to entry: The total data centre energy is measured in MWh; the energy is measured with energy metering

devices at the boundary of the data centre or points of generation within the boundary.

Note 2 to entry: This includes electricity, natural gas, hydrogen, bioethanol and district utilities such as supplied

chilled water or condenser water.
Note 3 to entry: Total annual energy includes supporting infrastructure.
[SOURCE: ISO/IEC 30134-2:2016, 3.1.7, modified.]
3.1.2
IT equipment energy consumption

energy consumed by equipment that is used to manage, process, store or route data within the compute

space

Note 1 to entry: IT equipment energy consumption is measured in MWh; examples for IT equipment are servers,

storage equipment, and telecommunications equipment.

Note 2 to entry: IT equipment energy use follows the same categories as in ISO 30134-2 Power usage effectiveness.

[SOURCE: ISO/IEC 30134-2:2016, 3.1.1, modified.]
3.1.3
water usage effectiveness

ratio of the data centre water consumption divided by the energy consumed by IT equipment

3.1.4
water use
water that is used by end-users for a specific purpose within a given territory

Note 1 to entry: For the purposes of this document, water use corresponds to the water consumption caused by

the processing of data in a data centre.

Note 2 to entry: Domestic use, irrigation or industrial processing are examples of a given territory.

Note 3 to entry: Water use is measured in water volume [m ] consumed.
3.1.5
reused water

water that is leaving the data centre boundaries for an alternative non-data-centre use

Note 1 to entry: The non-data-centre use of water is usually defined by local regulations for reuse.

3.1.6
potable water

water that is free from contamination and that is safe to drink or to use for food and beverage

preparation and personal hygiene
Note 1 to entry: Potable water is also known as drinking water.

Note 2 to entry: The definition of the quality criteria of potable water is usually subject to national or local

regulations; if there is no information about the criteria see Reference [2].
3.1.7
energy water intensity factor
amount of water that is used to produce energy
Note 1 to entry: Energy water intensity factor is measured in m per MWh.
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ISO/IEC FDIS 30134-9:2021(E)
3.1.8
water significance
amount of renewable freshwater that is available for each person each year

Note 1 to entry: Within the approach of this document, water significance is categorized by different levels of

water stress.
3.1.9
water stress
ability to meet human and ecological demand for freshwater
3.1.10
water quality

physical, chemical and biological characteristics of water concerning its suitability for an intended use

by humans, ecosystems or industrial processes
3.1.11
land consumption

loss of water permeability of the soil intended for use by humans, ecosystems or industrial processes

3.2 Abbreviated terms

For the purposes of this document, the abbreviated terms in ISO/IEC 30134-1 and the following apply.

DC data centre
dWUE design water usage effectiveness
EWIF energy water intensity factor
FI falkenmark indicator
iWUE interim water usage effectiveness
dWUE design water usage effectiveness
iWUE interim water usage effectiveness
peakWUE peak water usage effectiveness
PUE power usage effectiveness
pWUE partial water usage effectiveness
qWUE quality water usage effectiveness
WRF water reuse factor
WUE water usage effectiveness
3.3 Symbols
For the purposes of this document the following symbols apply:
E total data centre energy consumption (annual) in MWh
E IT equipment energy consumption (annual) in MWh
f energy water intensity factor (EWIF)
EWI
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ISO/IEC FDIS 30134-9:2021(E)
f water reuse factor (WRF)
r,w
f drainage factor of fully sealed surfaces
s(F)
f drainage factor of few sealed surfaces
s(f)
f drainage factor of heavily sealed surfaces
s(h)

I total water input from outside the data centre boundaries (annual) measured by total vol-

ume in m
I water input from rainwater
w,rw
I water input from water consumption of energy production
w,e
I water input from potable water
w,p
i falkenmark indicator (FI)
L data centre land consumption

O total water returned out of the data centre boundaries (annual) measured by total volume

in m
p population
s fully sealed surface
s few sealed surfaces
s heavily sealed surfaces
s surface runoff (annual) measured in m
run
U water usage of the data centre (annual) measured by total volume in m
U water reusage of the data centre (annual) measured by total volume in m
r,w
U industrial water reuse
r,w,I
U non-industrial water reuse
r,w,NI
η water usage effectiveness
U,W
η interim water usage effectiveness
U,W,i
NOTE Unlike for PUE, the unit of the energy used in WUE is MWh.
4 Applicable area of the data centre
WUE as specified in this document:

— is associated with the data centre infrastructure and IT equipment within its boundaries only;

— describes the water usage in relation to facilities with given environmental conditions, IT load

characteristics, availability requirements, maintenance and security requirements;

— measures the relationship between the total data centre water usage and the IT equipment energy

consumed.
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ISO/IEC FDIS 30134-9:2021(E)
WUE does not:

— account for efficiency of other resources such as human resources, space or CO ;

— provide a data centre productivity metric;
— provide a standalone, comprehensive efficiency metric;

— account for quality of the water reuse process outside the data centre boundaries;

— account for water down- or upgrade (reducing or improving water quality).
5 Determination of WUE

WUE provides a way to determine the water usage associated with data centres. A value of 0,0 indicates

that no water use is associated with the data centre‘s operations. WUE has no theoretical upper and no

theoretical lower boundary.
WUE is defined according to Formula (1):
η =
U,W
(1)
Annual water usage is calculated according to Formula (2) as:
U = I − O (2)
w w w

WUE may be applied in mixed-use buildings when measurement of the difference between water used

for the data centre and that for other functions is possible.
6 Measurement of WUE
6.1 General

All KPIs of the ISO/IEC 30134 series are defined within the boundaries of a data centre (see

ISO/IEC 30134-1).
6.2 Measuring actual water usage
6.2.1 Calculation, measurement period and frequency

The minimum calculation and measurement period requires twelve months of cumulative energy

and water values. Annualized data used to calculate WUE shall be documented. The annual energy

values for energy consumption of the IT equipment collected shall cover the same time period. It is not

necessary to define the frequency of measurement or assessments for the annual WUE determination,

as the annual water value is a continuous integration of energy consumed in that timeframe. Examples

of the calculation are shown in the Annex A.

NOTE The measurement or assessment frequency can be necessary for subsystem improvements (refer to

partial PUE), but is not required for WUE disclosures.
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ISO/IEC FDIS 30134-9:2021(E)
6.2.2 Categories of WUE
6.2.2.1 Introduction

The categories of WUE are defined, as shown in Table 1, to provide a defined route to refine the accuracy

of the WUE measured. WUE considers different water qualities and types of reused water. Category 3

requires additional reporting for regional water significance (level of water stress, in accordance with

Annex B) and land consumption (in accordance with Annex D).
Table 1 — WUE categories
Source Category 1 (WUE ) Category 2 (WUE ) Category 3 (WUE )
1 2 3
basic intermediate advanced

Considered water Physical water input of the Physical water input of the Water consumption of energy

input DC. DC. production and physical water
input excluding rainwater.

Considered water No water reuse; water input Water output of the DC for Water output of the DC with

output equates to water use. non-industrial reuse. measurement of non-industrial
and industrial reuse.
Additional report- No. No. Regional water stress level and
ing land consumption.

The water qualities for the water input are differentiated into potable and non-potable water. If there

exists a regional definition of water qualities for potable and non-potable, this shall be taken into

account. Otherwise definitions given in this document shall be applied. For water output, a distinction

is made between two typs of reused water: non-industrial reuse and industrial reuse. The definition

of the criteria for water reuse is usually subject to national or local regulation. The part of the water

output that is not reused is specified as used water.
6.2.2.2 WUE category 1: water usage without reuse

WUE is a metric considering total water consumption of the data centre. For the water output there is

no distinction of water use and water reuse in category 1 (see Figure 1). For WUE the significance of

regional water shortage and land consumption is not considered.
NOTE For the water input, potable water and non-potable water are considered.

WUE includes the water used at the DC location for operation of the data centre. This contains water

used for humidification and water evaporated on site for energy production or cooling of the data

centre and its support systems.
Figure 1 — WUE category 1
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ISO/IEC FDIS 30134-9:2021(E)
The WUE for category 1 is calculated using Formula (3):
η = (3)
U,W,1

For category 1, I is equal to U . For the water output in category 1 there is no reuse of water considered.

w w

This means that all the water that goes into the DC is leaving the DC as used water. WUE requires only

basic measurements for the water input. Measurements for the water output are not necessary. For

WUE an additional reporting of regional water stress level and land consumption is not necessary.

6.2.2.3 WUE category 2: water usage including reuse

WUE is a metric considering total water consumption of the data centre. For the water output there

is a distinction of water use and water reuse in category 2 (see Figure 2). For category 2, the reuse of

water refers exclusively to non-industrial water. For WUE an additional reporting of regional water

stress level and land consumption is not necessary.
Figure 2 — WUE category 2
The WUE for category 2 is calculated using Formula (4):
η = (4)
U,W,2
where U = I − U
w w r,w,I

WUE requires only basic measurements for the water input. The non-industrial water reuse shall be

measured. For WUE an additional reporting of regional water stress level and land consumption is not

necessary.
6.2.2.4 WUE category 3: water usage including energy and industrial reuse

WUE is a metric considering total water consumption of the data centre. For category 3, the water

input excluding used rainwater for DC operations shall be determined. In addition, water consumption

of energy production that is used by the data centre shall be determined (see Figure 3).

NOTE 1 By excluding rainwater from the water input, benefits for the use of collected water from rain are

considered. Used rainwater is part of the non-potable water input.

To determine the water consumption of energy production that is used by the data centre, the total

energy consumption of the data centre needs to be known. This value shall then be combined with an

EWIF (see Annex C) that is based on the water used to produce the energy. The data for the EWIF shall

be provided by the energy provider/producer.
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ISO/IEC FDIS 30134-9:2021(E)

If the actual energy water intensity values are not available from the local energy supplier, WUE

calculations are limited to the WUE and WUE methods. The EWIF values in Table C.1 are examples

1 2

and shall not be used in the absence of actual values from the local energy supplier.

NOTE 2 For used water in the delivery of the energy (e.g. electricity, heat, cold, natural gas, diesel fuel) there is

no physical water input at the data centre boundary. Water input for energy is always "used“ because electricity

is "lost“ (converted into heat).

For the water output there is a distinction of water use and water reuse in category 3. For category 3,

the reuse of water refers to non-industrial water and industrial water.

The reporting WUE considers the significance of regional water shortage and land consumption.

Figure 3 — WUE category 3
The WUE for category 3 is calculated using Formula (4):
η = (5)
U,W,3
where U = (I − I + I ) − (U + U )
w w w,rw w,e r,w,I r,w,IN
and where I = E × f
w,e DC EWI
7 Application of WUE

WUE can be used by data centre managers to monitor and report water consumption related to IT

energy consumption in the data centre.

This KPI can be used independently, but to obtain a more holistic picture of the resource effectiveness of

the data centre, other KPIs of the ISO/IEC 30134 series should be considered. Where WUE is reported,

the corresponding PUE value
...

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