National foreword

This Published Document is the UK implementation of ISO/TS 25128:2026.

The UK participation in its preparation was entrusted to Technical Committee GME/33, Small craft.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

This publication is not to be regarded as a British Standard.

Compliance with a Published Document cannot confer immunity from legal obligations.

This Published Document was published under the authority of the Standards Policy and Strategy Committee on 30 September 2026.

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

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 ISO 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).

ISO draws attention to the possibility that the implementation of this document may involve the use of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s) which may be required to implement this document. However, implementers are cautioned that this may not represent the latest information, which may be obtained from the patent database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.

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.

This document was prepared by Technical Committee ISO/TC 188, Small craft.

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.

Introduction

This document establishes a comprehensive test framework for assessing energy use of propelled small craft when navigating. The assessment encompasses both added energy, originating from the fuel or power source propelling craft, and non-added energy, comprising forces from wind, currents and waves influencing the craft’s movement.

The methodologies outlined not only enable consumers to evaluate energy use but also provide a tool for understanding the environmental impact and operational costs associated with various craft types.

The specific use of this document is twofold. It enables consumers to have a common and comparable baseline to evaluate trade-offs between craft models and/or propulsion systems, while enabling consumers to acquire knowledge about the most energy efficient operational conditions of a specific craft model and/or propulsion system.

In this document, energy use is a way of expressing energy in a common unit for use in comparisons and trade-offs between different craft models, propulsion systems and other modes of transport. The energy assessment to be determined includes some or all values reflected in the concept of total energy use.

This document does not include recommendations regarding the selection of energy sources. Furthermore, the energy assessment detailed herein excludes considerations related to the energy expended in the production of craft.

1 Scope

This document specifies requirements for the measurement, documentation and presentation of mechanical propulsion energy consumption for small craft underway, irrespective of the propulsion system, type of energy or hull characteristics.

This document does not apply to wind, wind-assisted hybrid and wave propulsion systems.

2 Normative references

3 Terms and definitions

4 General test conditions

4.1 Payload

4.2 Fuel type

4.3 Engine(s)/motor(s) and propeller(s)

4.4 Measurement and calculation method for craft energy consumption

4.5 System configuration

4.6 Energy consumption of non-essential systems

5 Test conditions

5.1 State of propulsion system

5.2 Sea state

5.3 Wind conditions

5.4 Air temperature

5.5 Water temperature

5.6 Salinity

6 Test procedures

6.1 General

6.2 Test Stage 1

6.3 Test Stage 2

7 Documentation of results

8 Presentation of results

8.1 Energy consumption

8.2 Range

Bibliography