When Should You Replace Your Consumer Unit?

Your consumer unit (sometimes called a fuse box or breaker panel) is the most important safety device in your home’s electrical system. It distributes power to every circuit and provides protection against faults that could cause electric shock or fire. But many homes in Kingston, Surrey, and South West London still have consumer units that are 15, 20, or even 30 years old.

Just because it still works does not mean it is safe.

What does a consumer unit actually do?

Your consumer unit does three things:

1. Distributes electricity from the incoming mains supply to individual circuits around your home.
2. Provides overcurrent protection through MCBs (miniature circuit breakers) that trip when a circuit is overloaded or short-circuited.
3. Provides earth fault protection through RCDs (residual current devices) that trip when current leaks to earth, which usually means someone is getting an electric shock or a cable is damaged.

Modern consumer units use RCBOs, which combine both functions in a single device for each circuit. This means a fault on one circuit only affects that circuit, not the whole house.

Signs your consumer unit needs replacing

Rewirable fuses

If your board has fuse carriers with exposed fuse wire rather than switches, it is significantly outdated. Rewirable fuses are slow to operate, can be fitted with the wrong rated wire, and offer no protection against earth faults.

No RCD protection

Open the cover of your consumer unit and look for a button marked “T” or “Test.” If there is no test button anywhere on the board, you have no RCD protection. This means there is no fast-acting defence against electric shock from a damaged cable or faulty appliance.

Plastic enclosure

Modern consumer units must be metal-clad to contain any internal arcing or fire. A plastic enclosure indicates an older installation that does not meet current standards.

Scorch marks or discolouration

Heat damage around terminals or the enclosure is a serious warning sign. This usually indicates loose connections or overloaded circuits and should be investigated immediately.

The board is full

If every slot in your consumer unit is occupied and there are no spare ways, adding a new circuit (for an EV charger, electric shower, or garden room) means the entire board needs to be replaced with a larger unit.

Your EICR flagged it

If an Electrical Installation Condition Report has classified your consumer unit as C1 (danger present) or C2 (potentially dangerous), replacing it is not optional. For landlords, C1 and C2 codes must be remedied within the timescales specified in the regulations.

What a modern consumer unit includes

A consumer unit installed to current standards (BS 7671, 18th Edition) should include:

• Metal enclosure to contain fire
• RCBO on each circuit for independent fault protection
• Surge Protection Device (SPD) to protect electronics from voltage spikes (required since 2022 for most new installations)
• Clear labelling of every circuit
• Adequate spare ways for future additions

How much does a consumer unit upgrade cost?

For a typical three-bedroom home in Kingston or Surrey, a consumer unit upgrade costs between £350 and £600. This includes the unit, all protective devices, fitting, testing, and certification.

The price varies depending on:

• The number of circuits (more circuits = larger board = higher cost)
• Whether earthing and bonding needs upgrading (common in older properties)
• Accessibility of the existing board

We provide a fixed quote after a site assessment.

When is a consumer unit upgrade essential?

You should strongly consider upgrading if:

• Your board is more than 15 years old
• It has no RCD protection
• You are planning a renovation, extension, or loft conversion
• You are installing an EV charger, heat pump, or electric shower
• An EICR has identified the board as unsatisfactory
• You are buying or selling a property
• You are a landlord and your board does not meet current standards

Common misconceptions

“If it works, it is safe.” A consumer unit can distribute power perfectly well while offering inadequate protection against faults. The board is not there to power your home. It is there to protect you when something goes wrong.

“Plastic boards are illegal.” They are not illegal to keep in service, but any new installation must use a metal enclosure. A plastic board is a clear indicator that the installation predates current regulations.

“I can just add an RCD.” Retrofitting an RCD to an old board is sometimes possible, but the result is usually less reliable than a purpose-built modern board with RCBO protection on every circuit.

Next steps

If you are not sure about the condition of your consumer unit, an EICR will assess it along with the rest of your fixed wiring. If an upgrade is needed, we provide a clear quote and can usually complete the work in a single day.

Contact us for a free consultation about your consumer unit. We cover Kingston, Richmond, Twickenham, Surbiton, and surrounding areas.