IEC TS 63498:2026

• Abstract:

  IEC TS 63498:2026 harmonizes the requirements and criteria for Key Performance Indicators (KPIs) and specifies KPIs of energy efficiency for entire electric railway system and its subsystems such as trains, contact lines, substations, both single and combined, clarifying the boundaries to be considered. This document applies to entire electric railway systems including non-traction loads.; The purposes are:; a) to determine and to trace the energy efficiency for a specific railway system;; b) to enable comparability between the different electric railway systems (on overall system level) by means of harmonized KPIs and system boundaries concerning energy efficiency;; c) to overview the characteristics of the electric railway system on an overall level with the structure of the electric railway system (including type, hierarchy and number of substations) and the KPIs (including the ranking) for transportation quality;; d) identification of the key impacts for energy efficiency as there are system flexibility, system functions and system features as basic characteristics for the entire electric railway system;; e) definition of harmonized processes and procedures for the simulation or calculation and validation of the system specific energy consumption (including energy feedback);; f) presenting the related and referenced standards and regulations for the electric railway system and its subsystems and their possible contribution to the overall target of the energy efficiency.

• Status: Published
• Publication Date: 29-Oct-2026
• ICS: 45.020 - Railway engineering in general
• Technical Committee: TC 9 - Electrical equipment and systems for railways
• Drafting Committee: PT 63498 - TC 9/PT 63498
• Current Stage: PPUB - Publication issued
• Start Date: 30-Oct-2026
• Completion Date: 02-Oct-2026

IEC TS 63498 ®
Edition 1.0 2026-10
TECHNICAL
SPECIFICATION
Railway applications - System energy efficiency

ICS 45.020 ISBN 978-2-8327-1486-7

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CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and abbreviated terms . 6
3.1 Terms and definitions . 7
3.2 Abbreviated terms. 11
4 Definition of energy efficiency for electric railway systems . 11
4.1 General description of energy efficiency of electric railway systems . 11
4.2 Inputs and outputs of electric railway systems . 14
4.2.1 General. 14
4.2.2 Inputs and outputs . 15
4.3 Identification of train operation parameters . 15
4.3.1 General. 15
4.3.2 Train-unit . 16
4.3.3 Infrastructure conditions . 16
4.3.4 Timetable and driving style . 16
4.3.5 Energy supply network characteristics . 17
4.3.6 Environmental conditions . 17
4.4 KPIs . 18
4.5 Boundaries . 18
5 Definition of efficiency KPIs and boundaries . 19
5.1 KPI 1 - Final energy consumption per mass transported (tkm) . 19
5.2 KPI 2 - Final energy consumption per offered transport (ask) . 19
5.3 KPI 3 – Final energy consumption per offered transport (vkm) . 20
5.4 KPI 4 - Final energy consumption per actual traffic output (pkm). 20
6 Definition of characteristic KPIs and boundaries . 20
6.1 KPI 5 - Share of energy consumption for parked trains . 20
6.2 KPI 6 - Energy recuperation rate . 21
6.3 KPI 7 - Efficiency of the railway power network . 21
Annex A (informative) Train operation parameters which influence KPIs . 23
A.1 General . 23
A.2 Train operation parameters . 23
A.2.1 Topography of the railway network. 23
A.2.2 Density of trains (number of trains per time-interval) . 23
A.2.3 Transportation capacity (tkm, pkm) . 23
A.2.4 Passenger load factor. 24
A.2.5 Comfort requirements . 24
A.2.6 Speed requirements . 24
A.2.7 Available energy-resources . 24
A.2.8 Architecture of the energy supply system . 24
A.2.9 Availability . 25
A.2.10 Conformity to ambient requirements . 26
A.2.11 Costs . 26

A.2.12 Technical regulations and standards . 27
A.2.13 Infrastructure properties that cannot be adapted . 27
A.2.14 System boundary-parameters (system-exploitation, parameterization) . 27
Annex B (informative) Example of traction loads and non-traction loads . 28
Bibliography . 29

Figure 1 – An example of physical boundaries for electric railway system . 12
Figure 2 – Input, output and driving parameters of electric railway system . 14

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Railway applications - System energy efficiency

FOREWORD
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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shall not be held responsible for identifying any or all such patent rights.
IEC TS 63498 has been prepared by IEC technical committee 9: Electrical equipment and
systems for railways. It is a Technical Specification.
The text of this Technical Specification is based on the following documents:
Draft Report on voting
9/3352/DTS 9/3384/RVDTS
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Specification is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
– reconfirmed,
– withdrawn, or
– revised.
INTRODUCTION
Energy efficiency is a key for preserving the environment and to save natural resources. Energy
policies of railway stakeholders are supported.
This document on electric railway energy efficiency (EE) specifies key performance indicators
and boundaries to assess the EE. This document establishes comparability between different
(overall) railway systems based on the key performance indicators and the boundaries, which
are defined in this document.
The purpose of this document is (in the following applications for energy efficiency in electric
railways) to
– consider energy efficiency in standardization work;
– identify which aspects of energy efficiency are relevant for standardization;
– use a structured and harmonized approach when addressing energy efficiency;
– use a systematic approach when addressing energy efficiency.

1 Scope
This document harmonizes the requirements and criteria for Key Performance Indicators (KPIs)
and specifies KPIs of energy efficiency for entire electric railway system and its subsystems
such as trains, contact lines, substations, both single and combined, clarifying the boundaries
to be considered. This document applies to entire electric railway systems including non-traction
loads.
The purposes are:
a) to determine and to trace the energy efficiency for a specific railway system;
b) to enable comparability between the different electric railway systems (on overall system
level) by means of harmonized KPIs and system boundaries concerning energy efficiency;
c) to overview the characteristics of the electric railway system on an overall level with the
structure of the electric railway system (including type, hierarchy and number of substations)
and the KPIs (including the ranking) for transportation quality;
d) identification of the key impacts for energy efficiency as there are system flexibility, system
functions and system features as basic characteristics for the entire electric railway system;
e) definition of harmonized processes and procedures for the simulation or calculation and
validation of the system specific energy consumption (including energy feedback);
f) presenting the related and referenced standards and regulations for the electric railway
system and its subsystems and their possible contribution to the overall target of the energy
efficiency.
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.
IEC 60850:2014, Railway applications - Supply voltages of traction systems
IEC 62313:2009, Railway applications - Power supply and rolling stock - Technical criteria for
the coordination between power supply (substation) and rolling stock
IEC 63593:20—, Railway applications - Rolling stock - Specification and verification of energy
consumption
3 Terms, definitions and abbreviated terms
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
– IEC Electropedia: available at https://www.electropedia.org/
– ISO Online browsing platform: available at https://www.iso.org/obp
___________
Under preparation. Stage at the time of publication: IEC FDIS 63593:2026.
3.1 Terms and definitions
3.1.1
apparatus
device or assembly of devices which can be used as an independent unit for specific functions
Note 1 to entry: In English, the term "apparatus" sometimes implies use by skilled persons for professional
purposes.
[SOURCE: IEC 60050-151:2001, 151-11-22]
3.1.2
boundary
set of criteria that specify the limit of the system or apparatus under consideration as well as
the interface or interaction between other adjacent systems
3.1.3
capital expenditure
CAPEX
expenditure on acquisitions of, or improvements to, assets
Note 1 to entry: Based upon accounting standards and organizational policy, CapEx usually relates to relatively
large (material) expenditure, which has benefits that are expected to last for more than 12 months.
[SOURCE: ISO/TS 55010:2024, 3.8]
3.1.4
comfort system
all equipment consuming energy for passenger and crew comfort belonging neither to the
traction equipment nor to traction auxiliaries, mainly for the provision of a comfortable
environment (for example lighting, heating, air conditioning, toilets, informat ion and
entertainment systems, laptop supplies)
Note 1 to entry: Comfort systems are split into two groups for use in this document: heating, ventilation and air
conditioning (HVAC) and other comfort functions.
3.1.5
contact line
conductor system for supplying electric energy to vehicles through current-collecting equipment
[SOURCE: IEC 60050-811:2017, 811-33-01, modified – the Note 1 to entry has been omitted.]
3.1.6
electric railway system
electric railway trains, power network used to provide energy for trains, and related systems
3.1.7
energy efficiency
EE
ratio or other quantitative relationship between an output of performance, service, goods or
energy, and an input of energy taking into account the driving parameters and the boundaries
EXAMPLE Conversion efficiency: energy required/energy used; output/input; theoretical energy used to
operate/energy used to operate.
Note 1 to entry: Both input and output are clearly specified in quantity and quality and are measurable.
[SOURCE: IEC Guide 118:2024, 3.1, modified – Rewording of Note 1 to entry.]
3.1.8
energy efficiency improvement
increase in energy efficiency as a result of technological, design, behavioural or economic
changes
[SOURCE: IEC Guide 118:2024, 3.4]
3.1.9
energy performance
measurable results related to energy efficiency, energy use and energy consumption
[SOURCE: IEC Guide 118:2024, 3.3]
3.1.10
energy storage system
ESS
physical system which is comprised of energy storage technologies such as batteries, double -
layer capacitors, flywheel, etc. and other equipment to connect the storage technologies to
traction equipment, including control, cooling and monitoring systems
3.1.11
environment
surroundings in which a product or system exists, including air, water, land, natural resources,
flora, fauna, humans and their interrelation
[SOURCE: IEC 60050-901:2013, 901-07-01]
3.1.12
electric traction power supply system
electric railway power network used to provide energy for trains
Note 1 to entry: The system includes
– contact line systems,
– return circuit of electric traction power supply systems,
– electric installations in power plants and substations, which are utilized solely for generation and distribution of
power directly to the contact line,
– electric installations of switching stations.
3.1.13
heating, ventilation and air conditioning system
HVAC
system to provide heating, ventilation and air conditioning for comfort
3.1.14
life cycle cost
LCC
total cost incurred during the life cycle
[SOURCE: IEC 60050-192:2015, 192-01-10, modified – Deletion of Note 1 to entry.]
3.1.15
passenger load factor
relation between the number of places occupied and the maximum number of places offered
Note 1 to entry: It can be calculated by dividing the passenger km by the available seat km.
3.1.16
motor vehicle
vehicle fitted with one or more traction motors
[SOURCE: IEC 60050-811:2017, 811-02-03]
3.1.17
operational expenditure
OPEX
expenditure incurred in the operation, maintenance and support of assets during their life cycle,
excluding capital expenditure
[SOURCE: ISO/TS 55010:2024, 3.9, modified – The definition has been reworded.]
3.1.18
regenerative braking
braking in which the energy produced by the motors is fed into the line or used
by on-board devices
[SOURCE: IEC 60050-811:2017, 811-06-25, modified – "electro-dynamic" and "contact" have
been removed, "into energy storage" has been replaced with "or used by", and the Note 1 to
entry has been omitted.]
3.1.19
rolling stock
all vehicles with or without motors
Note 1 to entry: Examples of vehicles include a locomotive, a coach and a wagon.
[SOURCE: IEC 60050-811:2017, 811-02-01]
3.1.20
traction load
energy consumed in electric vehicles
3.1.21
non-traction load
energy consumed in entire electric railway system excluding traction load
3.1.22
traction substation
substation
substation the main function of which is to supply an electric railway
system
Note 1 to entry: The synonym substation is used only when the context is clear.
[SOURCE: IEC 60050-811:2017, 811-36-02, modified – "traction" was replaced with "railway".]
3.1.23
train
combination of rolling stock coupled together
Note 1 to entry: Rolling stock includes banking locomotives.
[SOURCE: IEC 60050-811:2017, 811-01-08]
3.1.24
train-unit
group of vehicles including at least one motor vehicle and forming the smallest self -contained
unit, indivisible in service, of a multiple-unit train
[SOURCE: IEC 60050-811:2017, 811-02-09]
3.1.25
point of common coupling
PCC
point in an electric power system, electrically nearest to a particular load, at which other loads
are, or may be, connected
Note 1 to entry: These loads can be either devices, equipment or systems, or distinct network users' installations.
[SOURCE: IEC 60050-614:2016, 614-01-12]
3.1.26
passenger kilometre
pkm
performance measure equivalent to one passenger transported one kilometre
3.1.27
tonnes kilometre
tkm
performance measure equivalent to one tonne (1 000 kg) goods transported one kilometre
3.1.28
available seat kilometre
ask
capacity/production measure equivalent to one available seat transported one kilometre
3.1.29
vehicle kilometre
vkm
capacity/production measure equivalent to one vehicle transported one kilometre
3.1.30
state of energy
SOE
remaining energy to be discharged, normally expressed as a percentage of full energy as
expressed in relevant standards
[SOURCE: IEC 62864-1:2016, 3.1.14]
3.2 Abbreviated terms
AC alternating current
ask available seat kilometre
ATP-ATO automatic train protection - automatic train operation
CAPEX capital expenditure
DC direct current
EE energy efficiency
EFE energy feedback equipment
EMC electromagnetic compatibility
EMU electric multiple unit
ESS energy storage system
HQ headquarter
HVAC heating, ventilation and air conditioning system
KPI key performance indicator
LCC life cycle cost
OPEX operational expenditure
PCC point of common coupling
pkm passenger kilometre
SOE state of energy
tkm tonnes kilometre
vkm vehicle kilometre
4 Definition of energy efficiency for electric railway systems
4.1 General description of energy efficiency of electric railway systems
The electric railway system is defined by its boundaries and the requirements and expectations.
Boundaries are defined by:
a) the system-interfaces with the surroundings (definition of the railway system with structure);
b) the allowed exploitation of system-parameters.
On one hand there is the power network, and on the other hand there is the whole railway
system comprising of vehicles, the signalling system, the traction power supply system including
contact lines and tracks.
In between are electric transformers and substations, which can be interconnected via electric
distribution networks with an intermediate level.
The railway system itself can be physically divided mainly into:
– electric traction power supply system;
– rolling stock;
– signalling systems;
– passenger stations and freight yards;
– depots;
see Figure 1.
NOTE In this document, contact line systems include third rail (and fourth rail) systems, secondary device systems,
and ground level electric traction power supply systems. Pantograph includes collection shoes and antennas.
However, it is necessary to consider the quality of transport to minimize the energy consumption
per tkm or pkm, or both, in order to increase the efficiency of the traffic system. The chosen
signalling system and the driving method of the trains have an impact on the amount of average
power consumed by the vehicles.

Key
Components
1 Substation (rectifier) 2 Stationary energy storage system
3 EFE (inverter) 4 Station
5 Powering (consuming) train 6 Braking (regenerating) train
7 Parking vehicles
a Power network b Powering (consuming)
c Regenerating d Fuel cell / Diesel generator
e Onboard energy storage system f Wayside renewable energy sources
g Plugged shore supply
A) Non-traction load B) Depot
C) Point heating
NOTE Red arrows represent powering and blue arrows represent regenerated power. Green lines represent
boundaries (Solid lines indicate boundaries with outside the entire electric railway system, dashed lines indicate
boundaries within the entire electric railway system.).
Figure 1 – An example of physical boundaries for electric railway system
The EE of the electric railway system can be derived from a relationship between the electric
energy measured at each of the boundaries between
c) all coupling-connections to the power network at the related traction substations for the
electric railway system as input,
d) the traffic volume of the railway system as output, taking comfort levels (mainly
climatization) into account.
However, the EE of the entire electric railway system cannot be directly calculated from the
substation EE, overhead line system EE, and rolling stock EE separated by physical boundaries
and allowable parameter exploitations of the railway system.
The reasons are as follows:
e) The characteristics of electric railway systems on an overall level are different and often of
traditional origin for each of them.
f) The structure of the electric railway system, including type, hierarchy, and number of
substations
is different due to knowledge of system integration, defined contractually by traditional
customers.
g) The KPIs for the transportation quality are different and are taken into account, as there are
for:
passenger transportation – speed, mass of trains, density of trains, availability
(system-redundancies), service and comfort-functions
freight transportation – speed, density of trains, availability
(system-redundancies)
The EE of a railway system is improved and increased when the railway system is highly
utilized by many operators - for passengers and goods-traffic – (within its full system-
boundaries) increases the positive effect of concentration of all transportation-activities so
that the ratio of tkm per investment is improved.
h) Key-requirements and their ranking in the existing regulations, which have partial
characteristics of a law, are:
1) safety and minimization of hazards in a railway system;
2) availability for high exploitation of the railway system;
3) multi-national homologation and customer-acceptance;
4) costs (with contribution of EE), mainly OPEX and CAPEX for investment;
5) sustainability requirements;
6) further items.
Recent vehicles are sometimes equipped with ESS.
These stable regulations, based on juridical laws, are the basis for a successfully operated
railway system in this ordinary structure.
Therefore, this document presents and evaluates KPIs from various perspectives and defines
logical boundaries which are different from physical boundaries to determine the EE of an
electric railway system.
4.2 Inputs and outputs of electric railway systems
4.2.1 General
The approach of energy efficiency evaluation is based on IEC Guide 118. In evaluating the
energy efficiency of an electric railway system, it is first necessary to define the inputs and
outputs (see Figure 2). At the boundary between the electric railway system and the outside,
the fundamental input is the electricity supply obtained from the power network, both for
passenger and freight traffic. The output for passenger traffic is pkm transported. The output
for freight traffic is tkm transported.
The above fundamental inputs and outputs do not reflect factors such as distance, speed, and
comfort, which have a significant impact on the competitiveness of electric railway systems (see
Figure 2). In addition, the energy efficiency of electric railway systems is highly influenced by
transport distances and various train operation parameters such as topography and climate.

NOTE In this document, "train operation parameters" is used instead of "driving parameters" defined in
IEC Guide 118. Since in the electric railway system, the word "driving parameters" sometimes means how drivers
drive trains, such as accelerate ratio, maximum velocity, coasting and so on.
Figure 2 – Input, output and driving parameters of electric railway system
Traction energy for trains is travelling from origin to destination location including standstill
times on the way using the representative driving cycles. It includes energy related to traction
auxiliaries (control, cooling and leading driver's cab HVAC which is necessary for safe train
driving), HVAC for passengers, and other in commercial operation usually activated on-board
systems in normal operating mode.
For the traction and auxiliary energy in service, the defined timetable for the operation over a
specified line plays an important role. This document is therefore not a direct specification of
detailed driving styles, instead it provides a framework which allows freedom for the user to
propose sound solutions integrating a given mix of energy efficient technologies and driving
styles.
Electric railway systems compete with other modes of transportation, such as cars, ships, and
aircraft. Each mode of transportation has its own characteristics, and fair comparisons are not
easy to achieve. For example, electric railway systems cannot only consider the energy
consumed by one train. Power exchange through regenerative braking occurs between several
trains, and the power exchange between the electric railway system and the power network is
mutual rather than unidirectional.
Even among electric railway systems, comparisons related to energy efficiency are difficult to
establish due to the influence of operation parameters, as explained in Annex A. Specifically,
KPIs are quite diverse between several railways systems and remains dependent upon number
of system characteristics such as passenger flow or headway. However, use of KPIs is relevant
in case of management
...