Approximately 20,000 electrical fires occur in UK homes each year — around 50% of all accidental house fires. This guide covers arc fault detection devices (AFDDs), metal consumer units, smoke detector selection, and the warning signs of dangerous wiring that electricians and homeowners must recognise.
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Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.
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Electrical fires are one of the leading causes of accidental house fires in the United Kingdom. UK fire and rescue service data shows approximately 20,000 electrical fires in dwellings each year, accounting for around 50% of all accidental house fires. These fires cause a significant number of deaths, injuries, and billions of pounds of property damage annually.
Electrical fires in UK dwellings each year
Of accidental house fires are electrical in origin
Caused by faulty wiring or appliances
The risk is not evenly distributed across all properties. Older properties with deteriorating wiring, properties with overloaded circuits and extension leads, and properties with plastic consumer units and no RCD protection are at significantly higher risk. Properties with modern installations, metal consumer units, RCD protection, and appropriate smoke and heat detection are much safer.
For electricians, understanding the causes of electrical fires and the protective measures available is essential — both for advising customers and for ensuring that installed work does not contribute to the problem.
Every key change in the 2026 amendment on one page. AFDDs, TN-C-S protection, new schedule columns, model forms. Pinned on your van dash.
The majority of electrical fires fall into three categories: faulty wiring, faulty or misused appliances, and poor installation workmanship. Understanding these causes helps electricians identify and remediate risks during EICR inspections and new installation work.
Old rubber-insulated wiring (pre-1960s) becomes brittle and cracks, exposing conductors that can arc against each other or against earthed metalwork. Loose connections at socket outlets, switches, light fittings, and the consumer unit cause resistance heating and arcing. These faults are a leading cause of electrical fires in older properties.
Connecting more load than a circuit is rated to carry causes the cable to overheat. Standard twin-and-earth cable buried in thermal insulation has a significantly reduced current-carrying capacity. Overloaded extension leads in poor condition are a common ignition source.
Arc faults occur when electricity jumps between damaged conductors, corroded connections, or degraded insulation. Arcing generates extremely high temperatures (over 6,000°C) that can ignite surrounding materials — including plastic cable insulation and timber joists — even when the arc current is too low to trip a standard MCB. AFDDs are specifically designed to detect and interrupt these faults.
Incorrectly rated fuses, undersized cables, joints made in ceiling voids or wall cavities without a junction box, and cables damaged during installation (penetrated by nails or screws) are all workmanship issues that can cause fires years after the installation was completed.
Arc Fault Detection Devices (AFDDs) detect the electrical signatures of arcing faults — abnormal electrical discharges that can develop in damaged or deteriorating wiring and connections. AFDDs continuously monitor the current waveform in a circuit and use algorithms to distinguish between the normal current waveform of household loads and the irregular waveform characteristic of an arc fault.
BS 7671 (18th Edition) addresses the use of AFDDs. It recommends that AFDDs should be provided in specific circumstances:
Recommended, not mandated (in most cases): As of BS 7671:2018+A4:2026, AFDDs are recommended but not mandatory for most domestic installations in England and Wales. They are mandatory in some European countries. BS 7671 recommends that AFDDs should be considered and specified where the risk assessment indicates they would provide meaningful additional protection. Electricians should discuss AFDD options with customers during consumer unit replacements and new installations.
AFDDs are combined with MCBs in a single unit (AFDD+MCB) and replace standard MCBs on the ways they protect. They are currently more expensive than standard MCBs (typically £30 to £60 per way) but prices have reduced significantly and continue to fall. For bedroom circuits — where occupants are asleep and less likely to detect the early signs of a fire — the additional cost is a reasonable investment in safety.
Smoke and heat detectors provide the earliest warning of an electrical fire, giving occupants time to escape and contact the fire brigade before the fire spreads. The type of detector and its location are important — the wrong type in the wrong location provides false security and nuisance alarms.
Detects smoke particles by measuring light scattering. More sensitive to slow-burning, smouldering fires — the type of fire commonly associated with electrical faults in wall voids and roof spaces. Less prone to nuisance alarms from cooking than ionisation alarms.
Living rooms, hallways, bedrooms, landings
More sensitive to fast-flaming fires. Can give nuisance alarms from cooking and toast. Less effective at detecting slow-burning electrical fires in their early stages.
Older recommendations — optical preferred in most domestic locations now
Consumer units are the most common location for electrical arc faults in domestic installations — connections loosen over time, ageing protective devices develop faults, and the concentration of circuits in one location increases the risk.
Amendment 4 to BS 7671 (2015) introduced the requirement that consumer units in domestic premises must have a metal enclosure. This requirement exists because plastic consumer units, when subjected to an internal arc fault, can ignite — and the plastic enclosure then becomes fuel for the fire. A metal enclosure contains the arc and any combustion products within the enclosure, giving the protective devices time to operate and preventing fire spread.
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Try the safety tools freeHomeowners and electricians should be aware of the warning signs that indicate dangerous or deteriorating electrical wiring. Early identification of these signs can prevent an electrical fire.
An Electrical Installation Condition Report (EICR) is the most systematic way to identify electrical fire risks in an existing installation. The EICR assesses the condition of the fixed electrical installation — wiring, accessories, consumer unit, and earthing — and identifies deficiencies that could lead to fire or electric shock.
Deficiencies are classified as:
An EICR that reveals C1 or C2 deficiencies — such as deteriorating wiring, no earth bonding, or inadequate RCD protection — must be addressed promptly. An installation with known deficiencies and no remedial action taken represents a serious and preventable fire risk. Use the EICR certificate app to complete condition reports on site and provide customers with a clear, professional assessment of their installation's safety.
Electricians are uniquely positioned to advise homeowners on electrical fire prevention. Every consumer unit replacement, EICR, and new installation is an opportunity to discuss AFDDs, smoke alarm placement, RCD protection, and the condition of existing wiring.
Complete Electrical Installation Condition Reports on your phone. AI-assisted inspection guidance, code classification, and instant PDF for the homeowner. Every EICR is an opportunity to identify and address fire risks.
Consumer unit replacements (to metal enclosures with RCD protection and AFDDs) require an EIC. Complete it on site with AI board scanning and send the PDF to the homeowner immediately.
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