A forward look at the changes to BS 7671: 2018 - Amendment 4 (2026) and what electricians, designers, and inspectors need to know

The Institution of Engineering and Technology (IET) and BSI have confirmed the final content of BS 7671:2018 Amendment 4 (2026). This is the next major update to the UK’s national wiring regulations. Scheduled for release on 15 April 2026, this amendment reflects the rapid growth of energy storage systems, digital infrastructure, and advanced low‑voltage technologies across domestic, commercial, and industrial installations.

For electrical contractors, designers, and duty‑holders, this update will influence how new installations are designed, installed, tested, and certified.

In this blog I summarise the changes as I see and understand them ahead of the official publication date in April 2026. Please note that the information provided below is based on my understanding of what will be included. The final and published version may differ slightly, so please refer back to your copy of the new, shiny orange book when you receive it!

(IET and BSI publish Amendment 4 (2026) to BS 7671:2018 (IET Wiring Regulations)

🔧 Key technical changes in Amendment 4 (2026)

1. New chapter: stationary secondary batteries (Chapter 57)

Energy storage is now central to modern electrical systems. Amendment 4 introduces a comprehensive new chapter covering permanently installed battery systems, including:

• Shock protection

• Thermal management

• Fire safety and ventilation

• Isolation and emergency access

• Earthing and fault protection

• Requirements aligned with PAS 63100 for domestic systems

Where this will apply:

Domestic solar + battery systems  

• Installers must follow new rules for battery location, fire protection, and isolation.

  
  

Commercial UPS rooms  

• Designers will need to ensure correct ventilation, temperature control, and emergency access.

  
  

Industrial energy storage systems (ESS)  

• Clearer requirements for fault protection, segregation, and maintenance access.

Batteries densely installed in server rooms are a common sight. Amendment 4 aims to address these potential safety and efficiency concerns.

2. Functional earthing & equipotential bonding for ICT systems (Section 545)

A brand‑new section addresses the earthing and bonding needs of ICT equipment. This is now essential as buildings become more digitally integrated.

This includes:

• Functional vs protective earthing

• Bonding conductor sizing

• Continuity requirements

• Identification and labelling

Where this will apply:

Server rooms and data centres  

• Bonding arrangements must now follow updated ICT‑specific requirements.

  
  

Smart office buildings  

• Designers must ensure low‑noise earthing paths for sensitive equipment.

  
  

Industrial control systems  

• PLCs, automation panels, and networked sensors require compliant bonding to avoid interference.

We see lots of ICT equipment and control panels without any bonding. Hopefully the new section will eliminate these shortfalls.

3. Power over Ethernet (PoE) – new dedicated section (Section 716)

PoE is now widely used for lighting, CCTV, access control, and IoT devices. Amendment 4 introduces clearer guidance on:

• Cable current‑carrying capacity

• Heat build‑up in cable bundles

• Installation practices for higher‑power PoE

• ELV DC distribution over structured cabling

Where this will apply:

PoE lighting systems 

• Installers must consider cable grouping, current‑carrying capacity, and thermal effects.

  
  

CCTV networks in commercial buildings  

• Designers must ensure PoE power levels match device requirements and cable specifications.

  
  

Smart home installations  

• Higher‑power PoE devices (e.g., touch panels, access points) must follow new design rules.

PoE systems are becoming increasingly common. How often do designers consider the thermal aspects inherent in this technology?

4. Revised section 710: Medical Locations

Medical environments receive a significant update, including:

• Revised requirements for Group 1 and Group 2 locations

• Updated rules for insulation monitoring devices

• New Annex B710 for recording supplementary bonding resistance

• Stronger guidance for designers and testers

Where this will apply:

Hospital operating theatres  

• Testing documentation must now include updated bonding resistance values.

  
  

Dental surgeries  

• Installers must follow revised requirements for patient‑accessible zones.

  
  

Private healthcare clinics  

• Periodic inspection reports must reflect the new Section 710 testing schedule.

Medical locations will now need more comprehensive electrical testing and recording of the results.

5. Wiring systems – important clarifications (Chapter 52)

Ferromagnetic enclosures (Regulation 521.5.1)

• Clarifies rules to prevent eddy‑current heating.

• Conductors up to 200 A may pass through separate holes in ferrous enclosures if the assembly complies with BS EN IEC 61439.

• Above 200 A, a temperature‑rise test is required.

  
  

Premature collapse of cables (Regulation 521.10.202)

• Clarifies that the requirement is not intended to ensure circuit integrity during fire.

• Life‑safety systems remain governed by BS 5839, BS 5266, and BS 8519.

6. Coordination of electrical equipment (Section 536)

Regulation 536.4.202 now explicitly includes load curtailment when coordinating protective devices and assemblies.

7. Isolation & switching (Section 537)

• Firefighter’s switches must now be located based on the building’s fire strategy and fire engineer input.

• Regulation 537.4.2.1 deleted; 537.4.4 clarified.

8. Low‑voltage generating sets (Section 551)

• Clearer rules for generators operating in parallel with other sources.

• New requirements for protective devices in bidirectional energy flow.

• Stationary batteries are now treated as generating sets, not loads.

• Regulation Group 551.8 removed (content moved to Chapter 57).

9. Safety services (Chapter 56)

Updated to align with new battery requirements and modern fire‑safety strategies.

10. New energy efficiency chapter (Chapter 81)

A new framework for energy‑efficient design, covering:

• Smart load management

• Monitoring and metering

• Minimising losses

• Integration with renewables

This replaces the old Appendix 17.

11. Appendix updates

Appendix 4

New data for buried cables in ducts.

Appendix 6

Clearer model forms for EICRs — FI codes no longer automatically mean “unsatisfactory.”

Appendix 13

Fully redrafted to align with modern fire‑safety guidance (ADB, BS 9991, BS 9999).

Implementation Timeline

Date	Requirement
15 April 2026	Amendment 4 officially published
From publication	Can be used immediately
Six months later	BS 7671:2018+A2:2022+A3:2024 withdrawn

After the transition period, Amendment 4 becomes mandatory for:

• All new low‑voltage electrical installations

• Additions and alterations

• Periodic inspection and testing

Industry perspective

Mark Coles, Head of Technical Regulations at the IET, emphasises that Amendment 4 supports the integration of new technologies, especially energy storage, into everyday electrical work. He encourages the industry to prepare early for the transition.

Sebastiaan van Dort, Director of Energy and Sustainability at BSI, highlights the amendment’s role in supporting the UK’s 2030 clean‑energy goals and the wider move toward net‑zero infrastructure.

Why Amendment 4 matters

This update is more than a regulatory refresh, it reflects the future of electrical installation work in the UK:

• More battery storage

• More digital infrastructure

• More PoE‑powered systems

• More safety‑critical environments

• More emphasis on energy efficiency

• More integration with fire‑engineered building strategies

Electrical professionals who understand these changes early will be better positioned to design, install, and certify compliant systems in 2026 and beyond.