What Is BS 7671 Amendment 4? A Plain English Guide for Solar Owners

If you've looked into plug-in solar in the UK, you've probably heard the acronym BS 7671 Amendment 4. It sounds forbidding. Acronyms, amendment numbers, technical standards—it's the kind of thing that makes people's eyes glaze over.

But BS 7671 Amendment 4 is actually the reason plug-in solar is legal in the UK. It's worth understanding what it says—not in the technical jargon, but in plain English.

What Is BS 7671?

BS 7671 is the British Standard for electrical installation. Think of it as the rulebook for anyone who works with electricity in the UK. If an electrician installs wiring, a socket, or a lighting circuit in your home, they're following BS 7671.

It covers:

• Cable sizing (what thickness of wire for different currents)
• Earthing and bonding (how to ground systems safely)
• Circuit protection (fuses, circuit breakers, RCDs)
• Segregation (keeping high-voltage and low-voltage circuits apart)
• Testing and certification (how to verify an installation is safe)

BS 7671 is law in the UK. Any new electrical work must comply. If you hire an electrician, they'll reference BS 7671 by default. Insurance won't cover electrical work that violates it.

It's updated periodically (every 5–10 years) to reflect new technology and learning from incidents.

What's an Amendment?

Rather than completely rewriting BS 7671 every decade, the standards body (BSI) publishes amendments. These are focused updates addressing specific new situations.

Amendment 1 (2008) added requirements for extra-low-voltage systems. Amendment 2 (2015) updated arc-fault protection. Amendment 3 (2018) refined circuit segregation for smart systems. Amendment 4 (April 2026) is the first to address plug-in solar and small-scale embedded generation.

So Amendment 4 is a relatively small change to a large document. But that small change is significant—it's what makes plug-in solar legal.

What Does Amendment 4 Actually Say?

In technical terms, it adds clauses 531.4.3.3 and 531.4.3.4, plus supporting requirements in Section 7 (Special Installations or Locations). These clauses define how to safely connect small-scale generation (like plug-in solar) to a household electrical system.

Here's the plain English version:

1. Power Limit: 800W Maximum

You can connect a small-scale generation system (like a plug-in solar panel) to your household circuits, provided it doesn't exceed 800W.

Why 800W? Because:

• It's below the 1kW threshold where different grid protections kick in
• It's large enough to be useful (generates £200–£400/year in savings)
• It's small enough that every home's circuits can handle it safely
• It aligns with the EU and Germany's regulations (proof of concept)

If you want to install multiple panels, the total must not exceed 800W. So you could have two 400W panels, or four 200W panels, but not one 1000W panel.

2. RCD Protection: Type A Required

Your plug-in solar panel must be connected to a circuit protected by a Type A RCD (Residual Current Device).

What's an RCD? It's a device that detects if electricity is leaking where it shouldn't (e.g., through a person touching a live wire). If it detects a leak, it cuts the power in milliseconds, preventing electrocution.

There are different RCD types:

• Type AC: Detects traditional AC leakage. Older homes mostly have these.
• Type A: Detects both AC and smooth DC leakage (what solar inverters produce). Newer homes have these.

Why Type A? Because solar inverters produce a specific type of current (high-frequency DC) that AC RCDs don't reliably detect. By specifying Type A, Amendment 4 ensures that if your inverter has a fault, you're still protected.

If your home only has Type AC RCDs, you need to either:

• Upgrade to Type A (cost: £100–£300, done by an electrician)
• Use an RCD-integrated solar connector (some new kits have this built-in)

3. Circuit Connection: Dedicated or Ring Main

You can't plug your solar inverter into an extension cord or a multi-socket adapter. Amendment 4 says you must connect it to either:

• A dedicated circuit: A circuit breaker and cable that serves only the solar inverter. It runs directly from the consumer unit (your fuse box) to the solar outlet.
• A ring main circuit: An existing circuit that serves multiple sockets (like your kitchen worktops). But this circuit must be designed for the extra capacity.

Why this restriction? Because:

• Extension cords are fire hazards if power is flowing back through them (solar generates current, plugs weren't designed for bidirectional flow)
• Multi-socket adapters can overheat if exposed to reverse current
• A dedicated or properly rated circuit ensures the cable can handle the current without overheating

Most homes will use a dedicated circuit. The electrician adds a new circuit breaker to the consumer unit and runs a cable to a new socket. Cost: £200–£400.

4. Earthing and Bonding

Your solar system must be properly earthed (grounded). This means:

• The metal frame of the panel is connected to the earth conductor of your house's electrical system
• All exposed metal parts are bonded together
• There's a clear, unbroken path from the panel, through the cable, to the earth terminal in your consumer unit

Why? Because if the panel accidentally comes into contact with live voltage (a fault), earthing provides a safe path for that current to flow away without shocking anyone.

Amendment 4 doesn't add new earthing rules—it just specifies that existing earthing standards (from Section 5 of BS 7671) apply to plug-in solar.

5. G98 Notification

Here's the part that involves your DNO (Distribution Network Operator):

You must notify your DNO of your plug-in solar installation within 28 days of installation. You do this via a G98 form (G98/2 for microgeneration).

On the form you provide:

• Your name and address
• The type of generation (solar)
• The capacity (e.g., 400W)
• The inverter model and specifications
• Your confirmation that it complies with BS 7671

Why? Because the DNO needs to know where power is being generated and fed back into their network. This helps them:

• Manage grid stability
• Detect faults
• Plan network upgrades
• Comply with regulatory requirements

You don't need DNO permission (it's not like planning permission). You just notify them. They have 20 working days to respond with any concerns.

In practice, they almost never object to a 400–800W system. Objections are reserved for larger systems that could genuinely impact the local network.

6. Anti-islanding Protection

Your solar inverter must include protection that shuts down the system if the grid fails.

Imagine this: there's a power cut. Your solar panel is still generating. Without anti-islanding protection, power would flow into a de-energised grid—dangerous for electrical workers trying to repair the fault.

Modern solar inverters include anti-islanding protection as standard. They detect if the grid voltage disappears and immediately stop exporting power.

Amendment 4 requires this as a baseline safety feature. Most retail kits will have it.

What Amendment 4 Doesn't Require

Interestingly, Amendment 4 doesn't require:

• MCS certification: Professional installers don't have to be involved.
• Building Control approval: You don't need planning permission.
• Landlord consent: Renters can install (on balconies or walls) if wiring doesn't cross the tenant boundary.
• Inspection by a building control officer: You don't need council approval.

These absences are deliberate. Amendment 4 was written to enable DIY installation while maintaining safety.

However, you may choose to hire an electrician to:

• Check your earthing and bonding
• Install a Type A RCD (if you don't have one)
• Install a dedicated circuit
• Provide a compliance certificate

This costs £150–£300 but is optional (though recommended).

How to Check Your Home Is Compliant

Here's a simple checklist for plug-in solar compliance:

1. Do you have a Type A RCD? Check your consumer unit (fuse box). If you can't identify the RCD type, call an electrician to check.

2. Do you have spare capacity in your consumer unit? Can you add a new circuit breaker? If your board is full, an electrician can install a split load or relocation.

3. Is your earthing in good condition? If you had an EICR (electrical inspection) in the last 5 years, check that report. If not, get one.

4. Do you know your DNO? Find your DNO via your electricity supplier or at dnoperator.co.uk.

If the answer to 1 and 3 is yes, you're likely compliant. A new circuit and connection to the inverter will satisfy 2 and 4.

Cost to become Amendment 4 compliant (if you're not already):

• Type A RCD upgrade: £100–£200
• New dedicated circuit: £200–£300
• Electrician inspection: £150–£300
• Total: £400–£800 (one-time cost)

Add the cost of the solar panel itself (£400–£800) and you're looking at £800–£1,600 for a complete, compliant system.

What Amendment 4 Means for Electricians

If you're an electrician, Amendment 4 means:

• You can now certify plug-in solar installations as compliant with BS 7671
• You can install dedicated circuits specifically for solar
• You're liable if you sign off on work that violates the standard
• You should obtain specialist training or CPD on solar inverters and earthing

Most electricians are adapting to this. By mid-2026, expect training courses on plug-in solar installation to be widely available.

The Big Picture

BS 7671 Amendment 4 is a regulatory acknowledgement that plug-in solar is safe, legal, and here to stay.

It sets the baseline:

• Systems up to 800W
• Proper RCD and earthing protection
• DNO notification
• Anti-islanding safeguards

Within those boundaries, you're free to install solar however you like (or get an electrician to help).

It's not a barrier—it's a framework. It says: "Yes, you can do this. Here's how to do it safely."

For a step-by-step on the legal process and what comes next, read our guide to the UK plug-in solar law change.