Your consumer unit is the heart of your home's electrical safety. This guide covers when to upgrade, the difference between metal and plastic enclosures, Amendment 4 requirements, AFDDs and SPDs, Part P certification, and what you should expect to pay in 2026.
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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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A consumer unit — commonly called a fuse box, fuse board, or distribution board — is the central control point for your home's electrical installation. It receives the incoming supply from the electricity meter and distributes it to individual circuits throughout the property: lighting, socket outlets, cooker, shower, and any other dedicated circuits.
The consumer unit houses the protective devices that keep you safe. Modern consumer units contain MCBs (miniature circuit breakers) that automatically disconnect a circuit if it is overloaded or short-circuited, and RCDs or RCBOs that detect earth leakage (current flowing where it should not, such as through a person) and disconnect the circuit in milliseconds.
If your consumer unit still has rewirable fuses — where a piece of fuse wire melts to disconnect the circuit — or if it has a wooden back board, no RCD protection, or a plastic enclosure, it is seriously outdated and a safety risk. Upgrading the consumer unit is the single most impactful electrical safety improvement you can make to your home.
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.
There is no fixed legal requirement for homeowners to upgrade their consumer unit, but there are several situations where an upgrade is essential, strongly recommended, or required by the regulations:
Before January 2016, consumer units could be housed in plastic enclosures. Amendment 3 to BS 7671 (effective January 2016) changed this. All new or replacement consumer units in domestic premises must now be in a non-combustible enclosure — which in practice means a metal unit (Regulation 421.1.201). The current edition, BS 7671:2018+A4:2026, retains and builds on this requirement.
If your property has a plastic consumer unit that is otherwise functioning correctly and has adequate protection (MCBs and RCDs), there is no legal requirement to replace it immediately. However, if any work is done on the consumer unit — even adding a single circuit — the entire unit must be replaced with a metal enclosure.
The current edition, BS 7671:2018+A4:2026, consolidates the requirements for domestic consumer units introduced from Amendment 3 (effective January 2016) and extended by Amendment 4 (2026). Any consumer unit upgrade must comply with all of the following:
These requirements mean that a modern consumer unit upgrade typically involves a BS EN 61439-3 compliant metal enclosure, 30mA RCD or RCBO protection on all circuits (including every lighting circuit under A4:2026), and verification that the cable installation meets the concealed cable protection requirements.
Modern consumer units can include two additional types of protection device that go beyond the standard MCB/RCD/RCBO arrangement: AFDDs (Arc Fault Detection Devices) and SPDs (Surge Protection Devices).
AFDDs detect dangerous arcing faults — electrical sparks caused by damaged cables, loose connections, or crushed wiring. These arcing faults can start fires that normal MCBs and RCDs will not detect. BS 7671:2018+A4:2026 Regulation 421.1.7 recommends AFDDs in AC final circuits of a fixed installation to mitigate fire risk from arc fault currents. Currently a recommendation — expected to become mandatory in future amendments. Cost: approximately £50 to £80 per device.
SPDs protect against transient voltage surges from lightning, network switching, or supply faults. They divert surge energy safely to earth, protecting your electrical installation and connected equipment. BS 7671:2018+A4:2026 Regulation 443.4.1 requires SPD protection where the overvoltage could result in (a) serious injury to, or loss of, human life, or (c) significant financial or data loss — limb (b) was deleted by the A2:2022 Corrigendum (May 2023). For all other cases, protection must be provided unless the owner declares it not required because the risk is tolerable — so SPDs are not automatically mandatory for a typical domestic installation, but are strongly recommended best practice. A Type 2 SPD is fitted at the consumer unit. Cost: approximately £40 to £80 for the device.
Both AFDDs and SPDs are relatively inexpensive to include during a consumer unit upgrade. Discuss them with your electrician — the additional protection they provide is well worth the modest extra cost.
Elec-Mate's remedial estimator prices every component — the board, MCBs, RCBOs, AFDDs, SPDs, earthing, and labour.
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Start free trialA consumer unit upgrade is notifiable work under Part P of the Building Regulations in England and Wales. This means:
If a consumer unit upgrade is carried out by an unregistered electrician without Building Control approval, the homeowner can face enforcement action and difficulty selling the property. Always check that the electrician is registered with a competent person scheme before the work begins.
Consumer unit upgrade costs vary by location, number of circuits, and the specification of the new board. Here are typical prices for 2026:
All prices include labour, materials, testing, the Electrical Installation Certificate, and Building Control notification. Prices are higher in London and the South East and lower in other regions. Always get at least three written quotes and check the electrician's registration with a competent person scheme.
A consumer unit upgrade is a safety-critical job that must be done right. Here is what to look for when choosing an electrician:
Avoid electricians who quote significantly below the market rate — they may be cutting corners on the specification of the consumer unit, the quality of the devices, or the thoroughness of the testing.
Consumer unit upgrades are one of the most common jobs in domestic electrical work. They are straightforward for a competent electrician but involve significant paperwork: the EIC requires design information, a schedule of test results for every circuit, and all the installation details.
Elec-Mate eliminates the admin and lets you complete the entire workflow on site:
Photograph the existing consumer unit before you start. The AI reads the MCB ratings and circuit descriptions, giving you a baseline for the upgrade. Then photograph the new board after installation for the certificate record.
Complete the Electrical Installation Certificate on site. Voice-enter test results as you test each circuit. The app validates every entry against BS 7671 maximum values. Export as a professional PDF and send to the customer before you leave.
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