The key date
15 October 2026 is the changeover.
BS 7671:2018+A4:2026, often called the Orange Book, was published on 15 April 2026. During the six-month transition period, the previous A2:2022+A3:2024 edition remains valid. The IET states that the previous edition will be withdrawn on 15 October 2026.
For customers, the important point is that electricians need to keep their design, installation, inspection and testing work aligned with the current requirements as the industry moves onto Amendment 4.
Existing homes
Your wiring does not become unsafe overnight.
One of the most common misunderstandings is that every new edition of the Wiring Regulations forces existing homes to be upgraded immediately. That is not how the standard works.
The IET is clear that standards are not retrospective. An installation designed to an earlier edition is not automatically unsafe simply because requirements have since changed. An EICR assesses the actual condition of the installation, the effectiveness of its protection and whether any defects present a danger or potential danger.
Upgrades can still improve safety, particularly where older protection is limited, but a recommendation should be based on the installation in front of the electrician rather than the colour or age of the regulations book.
Major changes
Battery storage is one of the headline additions.
For domestic customers, the battery-storage chapter is likely to be the most visible change as home energy storage becomes more common alongside solar PV, time-of-use tariffs and backup-power systems.
Solar & batteries
Storage systems need more than a battery on the wall.
Modern battery systems can introduce two-way power flow, hybrid inverters, backup operation and different fault-current characteristics. Amendment 4 brings dedicated requirements for stationary secondary batteries, including design, power-conversion equipment, protective-device suitability, battery location, ventilation and fire-risk considerations.
If an existing solar or battery installation is being altered, expanded or investigated, the electrical side should be assessed as a complete system rather than treating the battery, inverter and consumer unit as unrelated items.
For landlords & businesses
Regulation changes do not replace condition-based inspection.
Landlords and businesses should still focus on the condition of their installation, appropriate inspection intervals, the findings of previous reports and any changes in use or equipment. A newer standard may affect how new work or alterations are designed, but existing installations should be judged on evidence and safety—not assumed to be defective solely because they pre-date Amendment 4.
Common questions
What customers usually want to know.
Does Amendment 4 mean my existing wiring is now unsafe?
No. Electrical standards are not retrospective. An older installation does not automatically become unsafe simply because a newer edition of BS 7671 has been published. Its actual condition, protection and test results still need to be assessed.
When does Amendment 4 become the only current edition?
BS 7671:2018+A4:2026 was published on 15 April 2026. The previous A2:2022+A3:2024 edition remains valid during the six-month transition and is withdrawn on 15 October 2026.
Why does Amendment 4 matter for batteries and solar?
The amendment introduces a dedicated chapter for stationary secondary batteries used for electrical storage and supply. It addresses matters including system design, power-conversion equipment, protective devices, battery location, ventilation and fire-risk considerations.