BS 7671 Amendment 4 Explained: What Changed on 15 April 2026

On 15 April 2026, the Institution of Engineering and Technology published an update to BS 7671 — the Wiring Regulations that govern every electrical installation in the UK. This update, Amendment 4, is the technical foundation that makes plug-in solar legal.

But it's often misunderstood. People think Amendment 4 means plug-in solar is now safe and ready. It doesn't. It means the framework is ready. The actual safety certification of specific products comes later (the BSI product standard, expected July 2026).

This guide explains what Amendment 4 is, what it changed, what it didn't change, and why both distinctions matter.

What Is BS 7671?

BS 7671 is the standard for electrical safety in the UK. It's published by the IET (Institution of Engineering and Technology), the professional body for electrical engineers in the UK.

BS 7671 covers every electrical installation: domestic rewiring, commercial electrical work, generator connections, solar installations, everything. It specifies safe practices for cables, earthing, circuit protection, switching, and every other electrical safety aspect. Building regulations in England, Scotland, Wales, and Northern Ireland all reference BS 7671 as the compliance standard.

If an electrician installs wiring that meets BS 7671, that installation is safe and compliant with building regulations. If it doesn't meet BS 7671, it's non-compliant and potentially dangerous.

BS 7671 is updated periodically as technology changes. The standard amendments are numbered: Amendment 1, Amendment 2, Amendment 3, Amendment 4. Amendment 4 is the latest.

What Was the Problem Before Amendment 4?

Before Amendment 4, BS 7671 didn't explicitly cover small solar systems plugged into standard wall sockets. This technology didn't exist when the regulations were written.

Plug-in solar — a 400W panel connected to an inverter, plugged into a three-pin wall socket — fell into a grey area. It was solar (vaguely covered), but it wasn't rooftop solar (the previous standard form). It was grid-connected (covered), but via a wall socket, not a dedicated solar isolator (not explicitly covered).

The IET and Distribution Network Operators said: "We don't have specific rules for this. We can't approve it until the regulations address it."

This wasn't safety obstruction — it was procedural. The regulations need to be clear before you can enforce them. You can't tell installers to follow rules that don't exist.

So Germany had legalised plug-in solar in 2012, built 1.2 million installations, and the UK regulators said: "Yes, we see it works in Germany. But our regulations need updating first."

That update is Amendment 4.

What Amendment 4 Changed

Amendment 4 adds a new section (roughly Section 7.12, depending on the exact structure) covering Distributed Generation from Small Photovoltaic Systems.

Specifically, it covers:

Connection point: Plug-in solar systems must be connected to a socket on a dedicated circuit. They can't be plugged into a shared socket (e.g., one that also powers your kitchen appliances). The socket must be on a 20A dedicated circuit (in most UK homes, this is already standard for certain appliances). This prevents issues where the small solar system accidentally powers appliances it's not designed for.

Earthing and bonding: The rules clarify how the earth (the safety reference) must be established for a solar inverter. Most plug-in solar systems bond to the earth through the three-pin plug, which is already safely designed.

Anti-islanding requirements: If the grid goes down, the inverter must automatically stop feeding power within a few seconds. This is called anti-islanding — it prevents the solar system creating an "island" of power that could electrocute an engineer working on the power lines. Amendment 4 requires this, and modern solar inverters have this built-in. It's tested as part of product certification.

Maximum system size: 800W is the cap. This is more about policy than wiring, but Amendment 4 codifies it.

RCD (Residual Current Device) protection: The circuit must have an RCD (a safety switch that cuts power if there's a fault), just like any other household appliance circuit.

Documentation and labelling: The installer must keep records of the installation, and the system must be clearly labelled for safety.

None of this is unusual. It's applying the same safety principles that already govern household electrics to this new application.

What Amendment 4 Didn't Change

This is crucial: Amendment 4 doesn't say which products are safe.

It doesn't say "EcoFlow's kit is safe" or "Anker's kit is safe." It says "if you're connecting a small solar system, here's how to connect it safely."

The question "which products are actually safe?" is answered by the BSI product standard, expected July 2026. That standard certifies specific inverters, panels, and complete systems.

Amendment 4 is the framework. The product standard is the list of approved products to use within that framework.

This is an important distinction because people sometimes think: "Amendment 4 is published, so all plug-in solar kits are now safe." Wrong. Amendment 4 is published, so the framework exists. Until the product standard is published and specific kits are tested and certified, no kit is approved for connection.

It's like publishing building regulations for extending a house. The regulations tell you how to extend safely. But you still need a specific plan checked by a building surveyor before you can start work.

Who Published It and Why?

The IET published Amendment 4. The IET is a professional engineering body, not a government agency, but building regulations across the UK incorporate BS 7671 by reference. So when the IET updates the standard, building regulations automatically update.

The IET didn't just decide to do this. The government's announcement on 15 March 2026 was the political signal. The IET then fast-tracked the amendment's publication to support the policy change.

This is normal: government policy → regulatory bodies update standards. The timeline was compressed because the amendment was ready to go — regulators had been preparing it for years. Once the political green light came, it was published in weeks.

The Electrician's Perspective

From the perspective of a qualified electrician, Amendment 4 means: "You can now legally install small solar systems under the Building Regulations, provided you follow the new section in BS 7671 covering small distributed PV systems."

An electrician can now:

• Assess the property for suitability
• Install the system meeting Amendment 4 requirements
• Certify the work under building regulations
• Issue the necessary paperwork

Most electricians are still getting up to speed on plug-in solar installations (it's new to them, even if not new to Germany), but the legal framework is now clear.

DIY installation is also possible (you don't need a qualified electrician for a low-voltage socket connection, just like you don't need one to plug in a kettle). But if you're uncomfortable with the technical side, an electrician can do it all.

What About the Product Standard?

The BSI is currently finalising the product standard for small PV systems. This standard will test specific inverters and complete kits to ensure they have proper anti-islanding protection, correct electrical safety, right cable specifications, etc.

Once published (July 2026 expected), manufacturers can test their products against it. Kits that pass will receive UKCA marking (UK safety certification). Only UKCA-marked kits can legally be connected, even though Amendment 4 has now made the framework available.

This is where the confusion intensifies: Amendment 4 opens the door. The product standard provides the list of approved products to use when you walk through that door.

The Timeline

Before 15 April 2026: No framework in BS 7671. Plug-in solar is in a regulatory grey area.

15 April 2026: Amendment 4 published. Framework is in place. You can now design a safe plug-in solar installation. You still can't connect an uncertified kit.

July 2026: BSI product standard published. Specific kits are tested and certified. You can now connect certified kits.

From July 2026 onwards: UKCA-marked kits are in shops. They meet Amendment 4 requirements and are tested against the BSI product standard. Safe to buy and connect.

Compliance and Building Regulations

From 15 April 2026, any plug-in solar installation must comply with BS 7671 Amendment 4 to meet Building Regulations. If someone installs a kit before Amendment 4 (rare, since Amendment 4 just came out), or without considering Amendment 4's requirements, that installation is non-compliant.

Local authorities could theoretically inspect and require removal, though enforcement is light. Insurance companies might refuse claims if an incident occurs and the installation wasn't Amendment 4-compliant.

The Honest Assessment

Amendment 4 is a genuinely important development. It removes the regulatory ambiguity that held back plug-in solar for thirteen years. From a technical and safety perspective, regulators finally said: "Yes, this is a safe, sensible thing to do, and here's how to do it."

But it's not the whole story. Plug-in solar isn't instantly legal for everyone from 16 April 2026. You still need:

• The BSI product standard (coming July 2026)
• Specific UKCA-marked products (coming July 2026)
• DNO notification (the G98 form)
• Landlord permission (if renting)

Amendment 4 is the critical piece, but it's not the final piece.

For More Detail

• Complete legal picture: see our main legal guide
• Product standard details: see our BSI standard guide
• DNO notification: see our G98 guide
• Installation: see our installation guide — coming soon

Amendment 4 is the technical foundation. July 2026 is when the whole structure is complete.