Arc Fault Detection in Solar Panels: How AFCI Protects UK Homes From Fire (2026 Guide)

Arc faults occur when electricity jumps across a gap in a damaged or loose connection, creating sustained electrical arcing that generates intense heat – potentially exceeding 3,000°C. In solar installations, arc faults are particularly dangerous because the DC system remains energised whenever the panels are illuminated, and DC arcs are harder to extinguish than AC arcs. Arc Fault Circuit Interrupters (AFCIs) monitor for the distinctive electrical signatures of arcing and shut down the system before a fire can start.

While arc fault detection is mandatory in the United States (NEC 690.11), it’s not currently required for residential solar installations in the UK. However, many quality inverters now include AFCI functionality as standard or as an option, and it’s increasingly specified for commercial installations and considered best practice for any system. As solar installations age and connections degrade, the value of arc fault protection becomes more apparent.

This guide explains what arc faults are, how they occur in solar systems, how detection technology works, the current UK regulatory position, and what to consider when choosing equipment with arc fault protection.

Quick Overview

Understanding Arc Faults

What Is an Arc Fault

Series vs Parallel Arc Faults

Why DC Arcs Are Dangerous

Causes of Arc Faults in Solar

Installation Defects

Installation defects are the dominant cause of UK solar fires. The Building Research Establishment (BRE), in research commissioned by the UK government, attributed roughly 36% of investigated UK PV fires to poor installation practices, with DC connectors and cabling repeatedly identified as the most fault-prone components – exactly the points where AFCI is most likely to detect an emerging arc.

Degradation Over Time

Physical Damage

Physical damage is a common arc-fault trigger that homeowners often miss. Storms can stress connections without obvious external signs, and small impacts to cells can introduce hairline cracks that develop into hot spots and arcing over years. See our guides on storm damage to solar panels and solar panel microcracks for the full picture on damage-related faults.

Component Failure

How Arc Fault Detection Works

Detection Principles

Arc Signatures

AFCI Operation

Response Time

Avoiding False Positives

The Challenge

Sources of False Triggers

How Good AFCI Avoids False Trips

UK Regulatory Position

Current Requirements (2026)

Relevant UK Standards

Comparison With Other Countries

Future Direction

AFCI Implementation

Where AFCI Is Located

Inverters With AFCI

If you’re choosing an inverter with arc fault detection in mind, our SolarEdge review covers SafeDC plus AFCI in detail, and our Enphase review explains why microinverter architectures inherently reduce DC arc-fault risk – both useful reference points whether you’re specifying a new system or evaluating an existing one.

Activation and Configuration

What Happens When Arc Is Detected

System Response

If your inverter throws an arc fault code, our solar inverter error codes guide can help you decode what each manufacturer’s specific message actually means and how urgent the trip is.

After Detection

Finding the Arc Source

For a structured approach to investigating any unexpected inverter behaviour – including suspected arc faults – see our solar panel fault finding guide, which walks through the typical diagnostic steps an installer or O&M provider will use.

Module-Level Solutions

Microinverters

For more on this approach, see our wider guide to microinverters for residential solar, which compares them with string and optimiser systems on safety and efficiency.

Power Optimisers

SafeDC and Similar

Benefits of Arc Fault Detection

Fire Prevention

The BRE Group’s overview of fire safety and PV confirms that fires in well-installed systems are rare in absolute terms but remain a meaningful risk where DC connections degrade undetected – the gap that arc fault detection is specifically designed to close.

Property Protection

For how arc-fault and fire-related events are treated in UK home insurance – including documentation that helps a claim go smoothly – see our solar panel insurance claims guide.

Early Problem Detection

Limitations of Arc Fault Detection

Detection Challenges

False Positive Issues

Not a Complete Solution

Choosing Equipment With AFCI

When to Specify AFCI

For listed and historic buildings, where the consequences of a roof fire are particularly severe, Historic England’s guidance on fire risk assessment for PV systems recommends arc fault detection as one of several mitigation measures alongside DC isolators, fire detection and careful cable management.

Inverter Selection

Cost Considerations

Installation and Commissioning

Installer Responsibilities

Commissioning Checks

Documentation

Responding to AFCI Trips

Homeowner Actions

Professional Investigation

False Trip vs Real Arc

Frequently Asked Questions

Basic Questions

Technical Questions

Summary

Arc fault detection provides an important safety layer for solar installations, identifying dangerous electrical arcing before it can cause a fire. Arc faults occur when electricity jumps across gaps in damaged or loose connections, creating temperatures that can exceed 3,000°C – easily capable of igniting roof materials. Unlike AC arcs, DC arcs don’t naturally extinguish, making them particularly hazardous in solar systems.

While arc fault detection isn’t currently mandatory for UK residential installations, it’s increasingly common as many quality inverters now include AFCI functionality as standard. The technology monitors DC current for the distinctive high-frequency signatures of arcing, distinguishing them from normal system noise, and shuts down the system within seconds if an arc is detected.

The primary value of AFCI is fire prevention, but it also serves as an early warning system for connection problems that could eventually become dangerous. When an AFCI trips, it indicates a real issue that needs professional investigation – not something to repeatedly reset and ignore. The cause might be a failing connector, damaged cable, or degrading junction box connection.

Quality installation remains the first line of defence against arc faults. Proper crimping, correct connector mating, appropriate torque on terminals, and careful cable routing prevent the conditions that lead to arcing. AFCI provides a safety net when connections degrade over time or problems develop despite best practices during installation.