Technical note · August 2026
On 15 April 2026 the IET and BSI published BS 7671:2018+A4:2026. Among its changes is a new Section 716 covering Power over Ethernet, together with a new section on functional earthing and functional equipotential bonding for information and communication technology equipment. The previous edition is withdrawn on 15 October 2026.
This note sets out what that means in practice for anyone specifying, procuring or installing a network that carries power.
At a glance
01 · Why it happened
When Power over Ethernet arrived it delivered 15.4 watts to a desk phone. That was a curiosity, not an electrical installation. Under IEEE 802.3bt Type 4, a single port now delivers up to 90 watts at the powered device, and a modern building distributes a great deal of its lighting, access control, surveillance, wireless and display estate over exactly that infrastructure.
A 48-port switch running Type 4 devices at capacity is distributing meaningful power through hundreds of small conductors bundled together in containment that was often sized for data alone. That is an electrical installation by any sensible reading, and the national wiring standard has now recognised it as one.
The practical consequence is straightforward: the design decisions that used to sit entirely with the data contractor now sit, at least partly, inside a standard that data contractors are not typically certified against.
The four PoE types
| Standard | Type | At the device |
|---|---|---|
| 802.3af | Type 1 | 12.95 W |
| 802.3at | Type 2 | 25.5 W |
| 802.3bt | Type 3 | 51 W |
| 802.3bt | Type 4 | 71.3 W |
Figures are the guaranteed minimum available at the powered device. Port output is higher — up to 90 W for Type 4 — with the difference dissipated as heat in the cable. That heat is the whole design problem.
02 · What actually changes
None of these is new engineering. What is new is that they now sit within the scope of the national wiring standard, which changes who is accountable for getting them right and what evidence is expected at handover.
03 · The procurement question
This is the part worth thinking about before your next tender goes out. A structured cabling contractor without electrical certification is now, in substance, contributing to a design governed by a standard it is not certified against.
In most cases that will pass without incident, as it has for years. But on a project within the higher-risk building regime, or anywhere a duty holder must demonstrate that appointees have the necessary skills, knowledge, experience and behaviours, it becomes a question at Gateway rather than a snag at handover.
There is no requirement for a single contractor to hold both capabilities. There is a requirement for somebody competent to own the electrical element, and for that to be a documented arrangement rather than an assumption that the other party is dealing with it.
Ask your contractor these five
A contractor who can answer all five without hesitating has read the amendment. One who cannot has not.
04 · Common questions
No. It means the electrical aspects of a PoE installation fall within the scope of BS 7671, and that somebody competent must own them. A data contractor can install the cabling; what must be documented is who is accountable for the load calculation, the bundle limits, the containment thermal performance and the earthing arrangements. Where one organisation holds both competencies, that accountability is simply not divided.
BS 7671:2018+A2:2022 incorporating A3:2024 is withdrawn on 15 October 2026. Installations designed before that date under the previous edition are not retrospectively non-compliant, but new design work from that point should be to A4:2026.
The standard applies regardless of size, but the practical significance scales with PoE loading. A handful of Type 1 devices on a short run presents essentially no thermal issue. Forty-eight Type 4 ports in a bundled riser is a different proposition entirely, and that is where the design attention belongs.
Not because of the amendment alone. It is worth reviewing where PoE loading has increased materially since installation — a Wi-Fi 7 refresh, for example, typically moves access points from Type 2 to Type 3 or Type 4, which can change the thermal picture on cabling that was designed for a lighter load.
Alongside Section 716 and the ICT functional earthing provisions, the amendment introduced a new section covering stationary secondary batteries, revised Section 710 for medical locations, and recognised protective neutral bonding arrangements. Section 716 is the change most relevant to network infrastructure.
Where a building falls within the higher-risk regime, duty holders must be able to demonstrate the competence of those appointed, and safety-relevant information must be maintained in the golden thread. A design decision now governed by BS 7671 is one a duty holder may reasonably be asked to evidence, which is an argument for recording the load assumptions rather than leaving them implicit.
Specification review
If you hold a cabling specification, performance schedule or framework rate card that pre-dates Amendment 4, send it over. We will review it against the current instrument set and return a marked-up commentary at no charge, with no obligation attached.*
This note is a plain-language summary prepared for clients and specifiers. It is not legal or design advice, does not reproduce the standard, and is not a substitute for the published text of BS 7671:2018+A4:2026, which should be consulted directly. Stated as at August 2026. Source: IET and BSI, publication of Amendment 4:2026 to BS 7671:2018, published 15 April 2026.