The Battery Storage Chapter Nobody's Talking About Yet

here's a specific kind of confusion that's been circulating across the electrical industry over the past several months, and it's worth untangling properly because it has real consequences for anyone specifying or designing electrical installations right now. The confusion concerns which amendment to BS 7671 actually governs what.

Important clarification

EV charging requirements are governed by Section 722, introduced in Amendment 1:2020 and substantially expanded by Amendment 2:2022 — mandatory since 27 March 2023. The amendment discussed in this article, Amendment 4:2026, is a separate and more recent update. It is not primarily about EV charging. Its headline content concerns battery storage, Power over Ethernet, and medical locations.

What actually arrived on 15 April 2026

The Institution of Engineering and Technology and BSI jointly published Amendment 4 (2026) to BS 7671:2018 on 15 April 2026, following content sign-off announced on 15 January 2026. The formal designation is BS 7671:2018+A4:2026, and it's being referred to within the industry as "the Orange Book," consolidating the previous amendments — A1:2020, A2:2022, and A3:2024 — into a single complete publication alongside the new content.

The headline addition is a genuinely new chapter on Stationary Secondary Batteries, covering the electrical storage and supply requirements for battery installations. This is the first time the Wiring Regulations have addressed battery storage at this scale and specificity, reflecting how rapidly battery energy storage systems have moved from a niche application into mainstream commercial and industrial infrastructure — driven substantially by the same renewable integration and grid-balancing pressures discussed throughout this series.

15 Apr

2026 — Amendment 4 published and immediately implementable

15 Oct

2026 — previous edition formally withdrawn

4th

Major amendment to the 18th Edition since 2018

Alongside the battery chapter, Amendment 4 introduces a new section on functional earthing and functional equipotential bonding specifically for information and communication technology equipment and systems — directly relevant to data centre and smart building infrastructure, where ICT earthing practices have historically been addressed through a patchwork of manufacturer guidance and informal convention rather than a single authoritative regulatory section. There's also a dedicated treatment of Power over Ethernet circuits, recognising that PoE now routinely delivers power levels the original wiring regulations never anticipated when written, and a major revision of Section 710 covering medical locations, including a new schedule for recording supplementary protective equipotential bonding test results.

The transition timeline that matters for live projects

Amendment 4 can be implemented immediately from its 15 April 2026 publication date. The previous version — BS 7671:2018+A2:2022+A3:2024 — remains valid and usable until its formal withdrawal six months later, on 15 October 2026. During this transition window, installations can be designed and certified to either version.

After 15 October 2026, the previous edition is no longer the recognised standard. Competent person schemes including NICEIC have been explicit that businesses will need to demonstrate access to and competence with Amendment 4 as a continuing condition of scheme registration from that date. Continuing to certify work against the withdrawn edition after that point creates genuine professional and legal exposure — work may not be certifiable to current standards, scheme registration could be jeopardised, and in the event of an incident, installations may fall short of the safety expectations the new amendment was specifically designed to address.

"For anyone working on commercial battery storage, data centre UPS systems, or PoE-heavy smart building infrastructure, this is the amendment that actually matters to your specification work over the next twelve months."

Why this matters specifically for data centre and critical infrastructure work

The three headline areas of Amendment 4 — battery storage, ICT functional earthing, and PoE — map almost precisely onto the infrastructure categories driving the current wave of UK data centre and grid investment discussed throughout this series. Battery energy storage systems are increasingly integral to data centre resilience strategy, both as UPS infrastructure and, in some cases, as grid-balancing assets in their own right. ICT functional earthing requirements speak directly to the dense, high-density electronic infrastructure inside any modern data hall. PoE's expanded power delivery underpins much of the smart building and IoT infrastructure increasingly specified alongside core IT and telecoms systems.

This means anyone scoping or specifying work in these categories with a completion date beyond October 2026 should, by the industry's own guidance, be designing to Amendment 4 from the outset, rather than designing to the outgoing edition and planning to update mid-project. The cost of switching design basis partway through a project is consistently higher than designing correctly from day one.

Practical steps for the transition period

• Audit current pipeline projects against their expected completion date. Any project genuinely likely to complete after 15 October 2026 should be reviewed against Amendment 4 requirements now, not closer to the withdrawal date.
• Prioritise Amendment 4 familiarisation for teams working on battery storage and ICT-heavy projects specifically, since these are the areas where the new content is most substantively different from previous editions, rather than treating it as a general refresher applicable equally everywhere.
• Review standard method statements, test sheets, and EICR templates for compatibility with the new chapters — particularly the additional data and recording requirements introduced for battery installations and medical locations.
• Confirm competent person scheme requirements directly with your specific scheme provider — NICEIC, NAPIT, or others — since audit and demonstration-of-competence expectations following the October 2026 withdrawal date may vary by scheme.

Source

IET & BSI joint press release, "IET and BSI officially publish Amendment 4 (2026) to BS 7671:2018," 15 April 2026; NICEIC Amendment 4 transition guidance; original content sign-off announcement, 15 January 2026.

The wider point, beyond the specific technical content, is a reminder of how quickly the regulatory ground can shift beneath an industry that's understandably been focused on a different, earlier amendment for the past few years. Section 722 and EV charging dominated the conversation from 2022 onward for good reason — it was a genuinely significant change at the time. But staying current means tracking what's actually new now, not what was new three years ago.