If your consumer unit is tucked away in a hallway cupboard, under the stairs or in a basement utility area, it is easy to forget about it until something trips. We see a lot of London properties where the board has not been touched for 25 or 30 years, yet the home now has far more electrical demand than it was ever designed for.
The question we are often asked is simple: when should you replace consumer units? The answer is not just based on age. You replace one when it no longer gives proper protection, when it fails inspection, when major electrical work is being carried out, or when the existing setup is unsafe for the way the property is now used.
Getting this wrong can cost more than the price of the job. A poor or outdated consumer unit can mean nuisance tripping, damaged appliances, failed landlord safety checks, insurance problems, fire risk and electric shock risk. Replacing a consumer unit is not a DIY job. In England, it is notifiable work under Part P of the Building Regulations and it needs proper testing and certification.
Why Consumer Units Matter More Than Most People Think
The consumer unit is the control point for the electrical installation. It divides the property into circuits, such as lighting, sockets, cooker, immersion heater, boiler supply, electric shower and outside power, then protects those circuits if there is a fault.
Older fuse boards often use rewireable fuses or cartridge fuses. They may still switch the lights on, but many do not provide modern RCD protection, which is designed to disconnect the supply quickly if electricity leaks to earth. That can happen through a damaged cable, a faulty appliance, water getting into an outside socket, or someone touching a live part.
Modern consumer units are usually fitted with RCBOs, which combine overload and residual current protection for each circuit. Many new boards also include surge protection devices, known as SPDs, which help protect sensitive equipment from voltage spikes. Domestic consumer units should also meet current BS 7671 wiring regulations, including suitable non-combustible enclosures in typical domestic settings.
In London housing stock, we often find a mix of old and new wiring behind the same board. A Victorian terrace in Chelsea might have newer kitchen wiring from a refurbishment, older lighting circuits with no CPC earth conductor, an added garden office supply, and a boiler spur that has been altered more than once. A consumer unit replacement has to take all of that into account, not just swap a box on the wall.
Check the Age, Type and Condition of the Existing Board
Start by looking at what you have, without removing any covers. If the unit has wooden backing, ceramic fuse carriers, rewireable fuse wire, cracked plastic, scorch marks, buzzing sounds, or no visible RCD test button, it needs checking by an electrician.
A plastic consumer unit is not automatically illegal in an existing home, but it may be a sign that the installation is older. What matters is whether the board is safe, correctly rated, properly enclosed, and suitable for the circuits it supplies.
If your board has only one main switch and no RCD protection, replacement is usually sensible, especially where sockets, bathrooms, kitchens, outside circuits or rental compliance are involved. If it trips often, smells hot, feels warm, or has signs of arcing, stop using affected circuits and call a qualified electrician promptly.
Arrange an Electrical Inspection Before Choosing a Replacement
A consumer unit should not be replaced blindly. We normally recommend an Electrical Installation Condition Report, known as an EICR, before the work if there is no recent certificate. This helps find faults that a new board may expose once modern protection is fitted.
In London, a domestic EICR is typically around £180 to £300 for a flat and £250 to £450 for a house, depending on size, access and number of circuits. Larger homes, HMOs, shops, offices and restaurants cost more because there are more circuits and distribution boards to test.
For rented homes in England, landlords must have the electrical installation inspected and tested at least every 5 years, or sooner if the report says so. For commercial premises, inspection intervals depend on the type of business, use and risk, with duties under the Electricity at Work Regulations 1989.
The inspection may find that the consumer unit itself is the main problem. It may also find weak insulation, borrowed neutrals on lighting circuits, missing main bonding, damaged accessories, or old wiring that needs repair before a modern RCD or RCBO board will behave properly.
Plan the New Consumer Unit Around the Property
A proper replacement starts with circuit planning. A small one-bedroom flat might need a compact 6 to 8 way board, while a larger Kensington townhouse with electric gates, underfloor heating, multiple kitchens, air conditioning and outdoor lighting may need a larger split arrangement or sub-board.
We usually prefer RCBO boards because a fault on one circuit does not usually take out half the property. That is helpful in London flats and family homes where losing all sockets or all lights at once is more than a nuisance.
The electrician should also check main earthing and bonding before fitting the new unit. Main bonding to gas and water services is often missing, undersized, or awkwardly routed in older properties, especially where meters have been moved into communal cupboards or basement vaults.
As a rough guide, a straightforward domestic consumer unit replacement in London often falls between £650 and £1,200 plus VAT for an 8 to 12 way RCBO board, including testing and certification. Extra remedial work, bonding upgrades, awkward meter positions, asbestos concerns, three-phase supplies, or out-of-hours work will increase the cost.
Isolate the Supply and Replace the Unit Safely
Replacing a consumer unit means working at the origin of the electrical installation. The power must be safely isolated, and in many cases this involves coordination with the supplier, meter operator, or Distribution Network Operator if the main fuse or service equipment is involved.
A competent electrician will label circuits, disconnect the old unit, inspect cable ends, fit the new enclosure securely, install the correct protective devices, and terminate each conductor properly. Loose terminations at a consumer unit are a common cause of overheating, so this part of the work has to be neat and exact.
This is not a place for guesswork. We have opened boards where lighting neutrals have been mixed, shower circuits have been underrated, and old rubber-insulated cables have started to crumble as soon as they were moved. If that happens, the job may need to pause while the unsafe section is repaired.
For a normal flat or small house, the power may be off for most of the working day. Larger homes and commercial premises may need phased work, temporary arrangements, or planned shutdowns outside trading hours.
Test, Certify and Notify the Work
Once the new consumer unit is fitted, the testing matters as much as the installation. The electrician should test insulation resistance, continuity, polarity, earth fault loop impedance, RCD or RCBO trip times, prospective fault current, and verify circuit details.
You should receive an Electrical Installation Certificate for the work. Because replacing a consumer unit is notifiable under Part P in England, the work should also be notified to Building Control, usually through the electrician’s competent person scheme if they are registered to self-certify.
Do not accept a board change with no certificate. It can cause problems when selling, letting, insuring, or proving compliance after a fault. For landlords and businesses, paperwork is part of the safety record, not an optional extra.
Labels should also be clear. We like to leave a circuit schedule that a normal person can understand, not scribbles such as misc sockets or old side. Clear labelling saves time when a fault occurs later.
Use These Timing and Cost Considerations Before You Book
The best time to replace a consumer unit is often before decorating, kitchen fitting, bathroom work, loft conversion, EV charger planning, or a major tenancy change. If the board is going to be moved, or new circuits are being added, it is cheaper and cleaner to plan the electrical work before finished surfaces are in place.
London properties bring their own access issues. We often have to work around communal meter cupboards, basement plant rooms, converted flats with shared freeholds, narrow hallways, ornate panelling, or consumer units boxed in by old carpentry. If the board is hidden behind shelving or built-in cupboards, clear access before the electrician arrives will keep the job moving.
Expect extra costs if remedial work is found. Main bonding upgrades might add around £150 to £300 depending on route and access. Replacing damaged accessories, sorting borrowed neutrals, splitting overloaded circuits, or upgrading old tails can add more. A three-phase commercial board or larger distribution board can run from about £1,500 to £4,000 plus VAT, sometimes higher where shutdown planning and out-of-hours work is needed.
Season also plays a part. In winter, any long power shutdown affects heating controls, pumps, fridges, freezers and home working equipment. For shops, clinics, restaurants and offices, we normally plan consumer unit work around trading hours so alarms, tills, servers and refrigeration are not disrupted unnecessarily.
You should call a professional rather than attempt anything yourself if you see scorch marks, repeated tripping, flickering across several circuits, a burning smell, exposed conductors, water near electrics, or signs that previous alterations were carried out badly. You should also call if you are buying a property with no electrical paperwork, preparing to let a flat, or planning work that adds load, such as a new kitchen, electric shower, garden office or heat pump.
Kensington Maintenance Services Ltd carries out inspection, fault finding, consumer unit upgrades and wider Electrical Services for homeowners, landlords and businesses across Kensington, Chelsea and nearby parts of London. If you want a realistic price before going ahead, you can get a quote with details of the property, the number of circuits if known, and a clear photo of the existing board.
Frequently Asked Questions
Q1: How often should a consumer unit be replaced?
There is no fixed replacement age, but many boards over 25 years old lack modern protection and should be inspected. Replace it if it is unsafe, damaged, unsuitable, or fails an EICR.
Q2: Can I replace a consumer unit myself?
No, this is not suitable DIY work. Consumer unit replacement is notifiable under Part P in England and must be tested, certified and notified properly.
Q3: Will a new consumer unit stop nuisance tripping?
Not always. Modern RCBO protection can reduce disruption, but tripping often points to an underlying circuit or appliance fault that must be found and fixed.
Q4: How long does a consumer unit replacement take?
A straightforward domestic board change usually takes one working day. Larger homes, older wiring, poor access, or commercial premises can take longer.
Q5: Do landlords need to replace old consumer units?
Landlords do not have to replace a board just because it is old, but the installation must be safe and pass the required electrical inspection. If the EICR records unsatisfactory findings linked to the board, remedial work is needed.
The simple rule is this: replace a consumer unit when it no longer protects the property properly, when an inspection shows it is unsafe, or when planned electrical work makes the old setup unsuitable. A neat new board is only worthwhile if the testing, earthing, bonding, certification and notification are done correctly, so if you are unsure about your existing fuse board or you need a safe upgrade in a London home, rental property or business premises, speak to Kensington Maintenance Services Ltd and contact us for professional services.