ISO/IEC 30134-2:2016

INTERNATIONAL ISO/IEC
STANDARD 30134-2
First edition
2016-04-15
Information technology — Data
centres — Key performance
indicators —
Part 2:
Power usage effectiveness (PUE)
Technologies de l’information — Centres de données — Indicateurs de
performance clés —
Partie 2: Efficacité dans l’utilisation de la puissance (PUE)
Reference number
©
ISO/IEC 2016
© ISO/IEC 2016, Published in Switzerland
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ii © ISO/IEC 2016 – All rights reserved

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 . 2
3.3 Symbols . 2
4 Applicable areas of the data centre . 3
5 Determination of power usage effectiveness (PUE) . 3
6 Measurement of power usage effectiveness . 4
6.1 Measuring energy consumption . 4
6.1.1 General. 4
6.1.2 Measurement period and frequency . 4
6.1.3 Meter and measurement requirements . 4
6.2 Categories of power usage effectiveness . 5
6.2.1 General. 5
6.2.2 Category 1 (PUE ) — Basic resolution . 5
6.2.3 Category 2 (PUE ) — Intermediate resolution. 5
6.2.4 Category 3 (PUE ) — Advanced resolution . 6
6.2.5 Measurement placement . 6
7 Reporting of power usage effectiveness . 6
7.1 Requirements . 6
7.1.1 Standard construct for communicating PUE data . 6
7.1.2 Example of reporting PUE values . 6
7.1.3 Data for public reporting of PUE . 6
7.2 Recommendations . 7
7.2.1 Use of PUE category . 7
7.2.2 Trend tracking data . 7
Annex A (normative) Energy measurements. 9
Annex B (normative) Calculation of PUE using various energy supplies .11
Annex C (normative) PUE derivatives .16
Annex D (informative) Interpretation of PUE and its derivatives .23
Bibliography .25
© ISO/IEC 2016 – All rights reserved iii

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. In the field of information technology, ISO and IEC have established a joint technical committee,
ISO/IEC JTC 1.
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).
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).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT), see the following URL: Foreword — Supplementary information.
The committee responsible for this document is ISO/IEC JTC 1, Information technology, Subcommittee
SC 39, Sustainability for and by Information Technology.
ISO/IEC 30134 consists of the following parts, under the general title Information technology — Data
centres — Key performance indicators:
— Part 1: Overview and general requirements
— Part 2: Power usage effectiveness (PUE)
— Part 3: Renewable energy factor (REF)
The following parts are under preparation:
— Part 4: IT Equipment Energy Efficiency for Servers (ITEEsv)
— Part 5: IT Equipment Utilization for Servers (ITEUsv)
iv © ISO/IEC 2016 – All rights reserved

Introduction
The global economy is now 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 the 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 manipulation and
storage are directly linked to increasing power consumption.
With this background, it is clear that data centre growth, and power consumption in particular, is an
inevitable consequence and that growth will demand increasing power consumption despite the most
stringent energy efficiency strategies. This makes the need for key performance indicators (KPIs)
that cover the effective use of resources (including but not limited to energy) and the reduction of CO
emissions essential.
Within the ISO/IEC 30134 series, the term “resource usage effectiveness” is more generally used for KPIs
in preference to “resource usage efficiency”, which is restricted to situations where the input and output
parameters used to define the KPI have the same units.
In order to determine the overall resource effectiveness or efficiency of a data centre, a holistic suite
of metrics is required. This part of ISO/IEC 30134 specifies power usage effectiveness (PUE), which
has become a popular metric to determine the efficient utilization and distribution of energy resources
within a data centre.
NOTE It is recognized that the term “efficiency” is to be employed for PUE but “effectiveness” provides
continuity with earlier market recognition of the term.
This part of ISO/IEC 30134 belongs to a series of 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 usage effectiveness or efficiency.
The ISO/IEC 30134 series does not specify limits or targets for any KPI and does not describe or imply,
unless specifically stated, any form of aggregation of individual KPIs into a combined nor an overall KPI
for data centre resource usage effectiveness or efficiency.
© ISO/IEC 2016 – All rights reserved v

INTERNATIONAL STANDARD ISO/IEC 30134-2:2016(E)
Information technology — Data centres — Key
performance indicators —
Part 2:
Power usage effectiveness (PUE)
1 Scope
This part of ISO/IEC 30134 specifies the power usage effectiveness (PUE) as a key performance
indicator (KPI) to quantify the efficient use of energy in the form of electricity.
This part of ISO/IEC 30134
a) defines the power usage effectiveness (PUE) of a data centre,
b) introduces PUE 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,
e) provides information on the correct interpretation of the PUE.
PUE derivatives are described in Annex D.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 30134-1:2016, Information technology — Data centres — Key performance indicators — Part 1:
Overview and general requirements
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.
3.1.1
information technology (IT) equipment energy consumption
energy consumed, measured in kilowatt-hour (kWh), by equipment that is used to store, process, and
transport data within the computer room, telecommunication room and control room spaces
Note 1 to entry: Examples are servers, storage equipment, and telecommunications equipment.
3.1.2
power distribution unit
PDU
equipment that allocates or partitions power for other energy consuming equipment
© ISO/IEC 2016 – All rights reserved 1

3.1.3
power usage effectiveness
PUE
ratio of the data centre total energy consumption to information technology equipment energy
consumption, calculated, measured or assessed across the same period
Note 1 to entry: Sometimes the inverse value of PUE, referred to as Data Centre Infrastructure Efficiency (DCiE),
is used.
3.1.4
partial power usage effectiveness
pPUE
derivative of PUE, which is the ratio of the total energy consumption within a defined boundary to the
information technology equipment energy consumption
3.1.5
designed power usage effectiveness
dPUE
derivative of PUE, which is a projected PUE determined by the design targets of the data centre
3.1.6
interim power usage effectiveness
iPUE
derivative of PUE, which is measured over a specified time other than a year
3.1.7
total data centre energy consumption
total energy consumption for all energy types serving the data centre, measured in kWh at its boundary
Note 1 to entry: Energy 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 and district utilities such as supplied chilled water or
condenser water.
3.2 Abbreviated terms
For the purposes of this document, the abbreviated terms given in ISO/IEC 30134-1 and the
following apply:
CRAC computer room air conditioner units
CRAH computer room air handler units
dPUE designed power usage effectiveness
DX direct expansion
iPUE interim power usage effectiveness
PDU power distribution unit
pPUE partial power usage effectiveness
r.m.s. root mean square
ROI return on investment
UPS uninterruptible power supply
3.3 Symbols
For the purposes of this document, the following symbols apply:
E total data centre energy consumption (annual) in kWh
DC
E IT equipment energy consumption (annual) in kWh
IT
2 © ISO/IEC 2016 – All rights reserved

4 Applicable areas of the data centre
Power usage effectiveness (PUE) as specified in this part of ISO/IEC 30134
— is associated with the data centre infrastructure within its boundaries only,
— describes the infrastructure’s energy efficiency relative to facilities with given environmental
conditions, IT load characteristics, availability requirements, maintenance, and security
requirement, and
— illustrates the energy allocation of a data centre.
When viewed in the proper context, PUE provides effective guidance and useful insight into the design
of efficient power and cooling architectures, the deployment of equipment within those architectures,
and the operation of that equipment.
PUE provides a means to determine
— opportunities for the improvement of the operational efficiency of a data centre,
— the improvement of the designs and processes of a data centre over time, and
— a design target or goal for new data centres across the anticipated IT load range.
PUE does not take into account the
— energy efficiency of the IT load, its utilization or productivity,
— efficiency of on-site electricity generation,
— efficiency of other resources such as human resource, space or water, and
— use of renewable energy resources or accounts for re-use of waste by-products (such as heat).
PUE is not a
— data centre productivity metric, and
— standalone, comprehensive resource efficiency metric.
Derivatives of PUE which are useful in certain circumstances as described in Annex C. PUE should not
be used to compare different data centres.
5 Determination of power usage effectiveness (PUE)
PUE is defined using Formula (1):
E
DC
PUE= (1)
E
IT
where
E is the total data centre energy consumption (annual), in kWh;
DC
E is the IT equipment energy consumption (annual), in kWh.
IT
By definition, the calculated PUE is always greater than 1.
Where the only energy source is from the electrical utility, then E is determined by the location of the
DC
utility meter. PUE may be applied in mixed use buildings that allow of the differentiation between the
energy used for the data centre and that for other functions. Alternatively, the derivative partial PUE
(pPUE) may be applied (see Annex C).
© ISO/IEC 2016 – All rights reserved 3

E includes, but is not limited to,
IT
— IT equipment (e.g. storage, processing and transport equipment), and
— supplemental equipment (e.g. keyboard/video/mouse (KVM) switches, monitors, and
workstations/laptops used to monitor, manage, and/or control the data centre).
E includes E plus all the energy that is consumed to support the following infrastructures:
DC IT
— power delivery [e.g. UPS systems, switchgear, generators, power distribution units (PDUs), batteries,
distribution losses external to the IT equipment, etc.];
— cooling system [e.g. chillers, cooling towers, pumps, computer room air handling units (CRAHs),
computer room air conditioning units (CRACs), direct expansion air handler (DX) units, etc.];
— others (e.g. data centre lighting, elevator, security system and fire detection/suppression system).
6 Measurement of power usage effectiveness
6.1 Measuring energy consumption
6.1.1 General
In order to calculate PUE, it is necessary to measure E and E . This is not a trivial task, especially
DC IT
within existing data centres which may require the installation of instrumentation to collect the data.
NOTE Although measurement of E and E are adequate to calculate PUE for the defined equipment and
DC IT
supporting infrastructure, more monitoring data of logical subsets is necessary to assess areas for potential
improvements and to evaluate the resulting improvements to PUE across the data centre.
6.1.2 Measurement period and frequency
The calculation of PUE requires the recording and documenting of E and E over a coincident period
DC IT
of 12 months. This part of ISO/IEC 30134 does not specify the frequency of measurements of E and
DC
E , since PUE is calculated on an annual timeframe. However, the frequency of measurement employed
IT
will define the timing of subsequent PUE calculations on a rolling annual basis.
6.1.3 Meter and measurement requirements
Measurement of E and E shall be undertaken using either
DC IT
— watt meters with the capability to report energy usage, or
— kilowatt-hour (kWh) meters that report the actual energy usage (true r.m.s), through the
simultaneous measurement of the voltage, current, and power factor over time.
NOTE Kilovolt-ampere (kVA), the product of voltage and current, is not an acceptable measurement. Though
the product of volts and amperes mathematically results in watts, the actual energy consumption is determined
by integrating a power factor-corrected value of volts and amperes. The frequency, phase variance, and load
reaction causes energy calculation difference between apparent energy and actual energy consumption. The
error is inherently significant when power delivery includes alternating current (AC). Kilovolt-ampere (kVA)
measurements may be used for other functions in the data centre; however, kVA is insufficient for efficiency
measurements.
4 © ISO/IEC 2016 – All rights reserved

6.2 Categories of power usage effectiveness
6.2.1 General
Three categories of PUE are defined as:
— Category 1 (PUE ) — provides a basic level of resolution of energy performance data;
— Category 2 (PUE ) — provides an intermediate level of resolution of energy performance data;
— Category 3 (PUE ) — provides an advanced level of resolution of energy performance data.
The higher categories provide progressively
— more accurate measurements of energy usage (as the measurements are made closer to the devices
that consume the energy), and
— greater scope for energy efficiency improvements.
Table 1 provides a summary of the locations for the measurement of IT equipment energy consumption
associated with each category. In all cases, the total data centre energy consumption is measured from
the utility service entrance that feeds all of the electrical and mechanical equipment used to power cool
and condition the data centre.
To properly assess PUE, it is critical to account for all systems that support the data centre, in addition
to the environmental conditions, reliability, security and availability requirements independent of
which PUE measurement category is chosen (see ISO/IEC 30134-1:2016, Annex A).
Table 1 — PUE categories
PUE PUE PUE
1 2 3
Location of IT equipment energy con- IT equipment
a b
UPS output PDU output
c
sumption measurement input
a
Includes impact of fluctuating IT and cooling loads.
b
Excludes impact of losses associated with PDU transformers and static switches.
c
Excludes impact of losses associated with electrical distribution components and non-IT related devices.
6.2.2 Category 1 (PUE ) — Basic resolution
The IT load is measured at the output of the UPS (or equivalent) equipment and may be read
— from the UPS front panel,
— through a meter on the UPS output, and
— in cases of multiple UPS modules through a single meter on the common UPS output bus.
The incoming energy is measured from the utility service entrance that feeds all of the electrical and
mechanical equipment used to power, cool, and condition the data centre.
If UPS or an equivalent power failure ride through or conditioning unit is not available, other categories
may apply.
6.2.3 Category 2 (PUE ) — Intermediate resolution
The IT load is measured at the output of the PDUs within the data centre and is typically read from the
PDU front panel or through a meter on the PDU output (with or without transformer, the measurement
point is then after the transformer). Individual branch circuit measurement is also acceptable for
Category 2.
© ISO/IEC 2016 – All rights reserved 5

6.2.4 Category 3 (PUE ) — Advanced resolution
The IT load is measured at the IT equipment within the data centre. This can be achieved either by
metered rack (e.g. plug strips) that monitors aggregate set of IT systems or at the receptacle level or by
the IT device itself. Note that non-IT loads shall be excluded from these measurements.
6.2.5 Measurement placement
Each category enables progressively improved accuracy of measurement of IT equipment energy
consumption, as the measurements are taken closer to the IT devices that consume energy.
7 Reporting of power usage effectiveness
7.1 Requirements
7.1.1 Standard construct for communicating PUE data
In order for a reported PUE to be meaningful, the reporting organization shall provide the following
information:
— data centre (including the boundaries of the structure) under inspection;
— PUE value;
— category.
The PUE category shall be provided as a subscript to the name of the metric, e.g. PUE for a Category
2 value.
7.1.2 Example of reporting PUE values
Using the construct of 7.1.1, Table 2 provides examples of specific PUE designations and their
interpretation.
Table 2 — Examples of PUE reporting
Example PUE designations Interpretation
Data centre X, PUE (2012–12–31) = 2,25 In the year 2012, the PUE value of data centre X was 2,25. It was
a Category 1 PUE.
Data centre Y, PUE (2013–06–30) = 1,75 In the period 2012–07–01 to 2013–06–30, the PUE value of data
centre Y was 1,75. It was a Category 1 PUE.
Data centre Z, PUE (2013–12–31) = 1,50 In the year 2013, the PUE value of data centre Z was 1,50. It was a
Category 2 PUE.
7.1.3 Data for public reporting of PUE
7.1.3.1 Required information
The following data shall be provided, when publicly reporting PUE data:
— contact information;
Only the organization’s name or contact should be displayed in public inquiries.
— data centre location information (address, county or region);
6 © ISO/IEC 2016 – All rights reserved

Only state or local region information are required to be displayed in public inquiries.
— measurement results: PUE with appropriate nomenclature including category designation.
7.1.3.2 Supporting evidence (where required by authorities having jurisdiction)
Information on the data centre which shall be available upon request as a minimum includes
— organization’s name, contact information and regional environmental description,
— measurement results: PUE with appropriate nomenclature,
— E and E ,
DC IT
— start and measurement(s) dates the assessments were completed,
— the accuracy level (IEC 62052 series and IEC 62053 series provide a reference for measurement of
electrical energy),
— report on the size of computer room, telecom room and control room spaces, and
— external environmental conditions consisting of minimum, maximum and average temperature,
humidity and altitude.
7.2 Recommendations
7.2.1 Use of PUE category
The PUE category should be appropriate to the expected value of PUE.
— PUE > 1,50: Category 1 to Category 3
— 1,50 ≥ PUE > 1,20: Category 2 or Category 3
— PUE ≤ 1,20: Category 3
7.2.2 Trend tracking data
The following information may be useful in tracking the PUE trends within a data centre:
— data centre size (facility square metres);
— total data centre design load for the facility (e.g. 10,2 MW);
— name of the possible auditor and method used for auditing;
— data centre contact information;
— data centre environmental conditions;
— data centre’s mission;
— data centre archetype percentages (e.g. 20 % web hosting, 80 % email);
— data centre commissioned date;
— numbers of servers, routers, and storage devices;
— average and peak server CPU utilization;
— percentage of servers using virtualization;
— average age of IT equipment by type;
© ISO/IEC 2016 – All rights reserved 7

— average age of facility equipment by type (cooling and power distribution equipment);
— data centre availability objectives (see ISO/IEC 30134-1:2016, Annex A);
— cooling and air-handling details.
NOTE Other KPIs within the ISO/IEC 30134 series can assist in the recording of the above information.
8 © ISO/IEC 2016 – All rights reserved

Annex A
(normative)
Energy measurements
A.1 Measuring energy and calculating power usage effectiveness
In Figure A.1, total data centre energy consumption is measured at or near the data centre’s utility
meter(s) to accurately reflect the energy entering the data centre (see Annex B for other energy sources)
in order that the measurement represents the total energy consumed in the data centre.
Building load - demand from grid
Power
• switchgear
IT equipment
• UPS
IT load
energy
• battery backup
• servers
consumption
Total data centre
• other
• storage
energy
E
E Cooling
• network telecoms equipment
DC IT
consumption
• chillers
• other
• CRACs
• other
Figure A.1 — Schematic of PUE calculation from measurements
Only the data centre portion of a facility’s utility consumption meter relevant to the data centre shall
be measured, since including in the calculation any energy that is not intended to be consumed in the
data centre would result in a non-compliant PUE calculation. For example, if a data centre resides in
an office building, the total energy drawn from the utility will be the s
...