Consumer Unit Replacement or Full Rewire? A London Homeowner’s Guide

A consumer unit replacement changes the equipment that distributes and protects the electrical circuits. A rewire replaces the fixed wiring serving some or all of the property.

Suitable existing wiring may be retained when the consumer unit is replaced. Conversely, a new board cannot repair damaged cable insulation or make an unsuitable circuit adequate for a new load.

There are usually four possible approaches to discuss:

The aim is to establish an appropriate scope, not to assume that the largest project is always necessary.

If you notice smoke, burning, electric shocks or signs of serious overheating, seek urgent professional help rather than waiting for a planned survey. Do not remove electrical covers or repeatedly reset a device that keeps tripping. If there is a fire, leave the property and call 999.

The consumer unit is the point from which the property’s circuits are distributed and protected. Many people still call it the fuse box or fuse board, even when it contains circuit breakers rather than traditional fuses.

A replacement may provide an opportunity to improve circuit separation, introduce appropriate modern protection and make the installation easier to identify and manage.

You may encounter several terms in the specification:

• MCB: a circuit breaker providing protection against overloads and short circuits.
• RCD: a general term for a device that detects an imbalance associated with current leaking from its intended path.
• RCBO: a device combining residual-current and overcurrent protection, commonly used to protect individual circuits.
• SPD: a surge protective device intended to limit transient overvoltages.
• AFDD: an arc fault detection device, specified where required or appropriate for the installation.

These devices perform different functions. Their selection should follow the electrical design, applicable requirements and equipment being supplied, rather than a generic shopping list. NICEIC explains consumer units and their protective devices.

However, the board is only one part of the installation. Replacing it does not automatically renew cables, correct unsuitable alterations elsewhere or replace damaged sockets and switches.

It also does not turn every existing circuit into a newly installed circuit. The quotation and certification should make the actual extent of the work clear.

For information about the service itself, see our consumer unit replacement in London.

A useful assessment answers more than “how many circuits are there?”

It should establish what is already installed, what can reasonably remain and what would prevent the proposed work from being completed safely.

Existing records and the history of the property

Provide any previous Electrical Installation Condition Reports, installation certificates and information about alterations.

A recent kitchen installation, a loft conversion and an older lighting circuit may all have different histories. One date cannot necessarily describe the whole property.

Tell the electrician about intermittent problems too. A circuit that occasionally trips, a socket that becomes unusually hot or work carried out without documentation can affect the investigation.

Inspection and testing

Electrical Safety First recommends an EICR before a planned consumer unit replacement. Where the customer does not proceed with a full EICR, its guidance still requires a pre-work survey; replacing the board without assessing the affected installation is not an acceptable shortcut.

The assessment considers matters such as existing defects, wiring condition, protective conductors, earthing and bonding, supply arrangements and relevant electrical test results. Identified dangerous circuits require appropriate action before reconnection. Electrical Safety First — consumer unit replacement guidance

Access and limitations

An EICR records the condition of an installation within its agreed extent and limitations. It is not a promise that every centimetre of concealed cable has been exposed.

A quotation visit, a visual inspection, an EICR and fault finding are also different activities. Ask which service is being proposed and what it will establish. NICEIC — understanding an EICR

A photograph can help with initial planning. It cannot establish the condition of hidden wiring.

No. Age is a reason to investigate, not a complete diagnosis.

Electrical Safety First advises that the condition of an installation matters more than its age when deciding whether rewiring is necessary. A suitably assessed older installation is not automatically condemned because it was installed in a particular decade. Electrical Safety First — age and condition

The reverse is equally important: newer-looking accessories do not prove that the cables behind them are recent or suitable.

A refurbished room might have contemporary sockets connected to much older wiring. A modern consumer unit may have been installed while substantial parts of the original installation were retained.

Some older cable types deserve particular caution. Electrical Safety First strongly recommends replacing lead-sheathed or rubber-insulated cables before a consumer unit change because handling and retermination can worsen deteriorated insulation. The extent of that wiring must be established rather than assumed. Electrical Safety First — older cables and board replacement

The useful question is therefore: what evidence supports retaining or replacing each relevant part of the installation?

A smaller scope may be appropriate where the existing circuits are suitable for continued use and the shortcomings can be addressed without replacing wiring throughout the property.

That might mean repairing a localised defect, upgrading the consumer unit, improving identified protective arrangements or carrying out a combination of these measures.

For example, a damaged accessory should not automatically become a proposal to replace every circuit in the home. Equally, a board upgrade should not be sold as the complete solution when tests have identified faults elsewhere.

Repeated tripping also needs diagnosis. The cause can be connected equipment as well as the fixed installation. A replacement board is not a substitute for finding the cause. IET — consumer units and tripping devices

Ask for the proposed work to be separated into:

• what is necessary to address the findings;
• what is needed for your planned alterations;
• what is an optional improvement.

That distinction helps you understand the recommendation without confusing essential work with desirable upgrades.

A partial rewire replaces a defined portion of the existing installation while retaining other parts that have been assessed as suitable.

It can be a sensible approach where the problem is concentrated in particular circuits, or where a refurbishment affects only part of the property.

The scope needs more precision than “rewire the kitchen” or “do the upstairs”.

Electrical circuits do not always follow room boundaries. One circuit may serve several rooms, while a kitchen may contain multiple circuits and connections with different purposes.

A clear proposal identifies:

• which circuits or cable sections will be replaced;
• which existing circuits will remain;
• any consumer unit or protective-device work;
• how the retained and replacement parts will be assessed and connected;
• the inspection, testing and documentation included.

Adding a new circuit is not necessarily the same as rewiring an existing one. A project may need new circuits, alterations and partial rewiring in different combinations.

Can the work be completed in stages?

Sometimes, provided the stages are designed as a coherent project and each completed stage leaves the installation safe for use.

The first phase should account for the intended final layout. Otherwise, a newly installed cable route, board or accessory position may need changing again during the next phase.

Ask for the total staged scope as well as the first-stage price. Repeated mobilisation, access and reinstatement can affect the overall cost.

Budget is a valid planning consideration, but it cannot justify leaving identified dangers in service.

A full rewire may be justified where deterioration or unsuitable work is widespread, where substantial parts of the installation cannot reasonably be retained, or where the proposed refurbishment changes the electrical layout extensively.

It also provides an opportunity to agree the finished arrangement as a whole: sockets, lighting, fixed appliances, controls and other specified systems.

There are two different reasons for choosing this route:

Condition-led replacement: the existing installation requires extensive renewal.

Refurbishment-led replacement: some existing wiring might remain serviceable, but the planned layout and building programme make comprehensive replacement a practical choice.

Your quotation should explain which applies. An elective redesign should not be presented as a legal requirement without justification.

“Full rewire” must also have a defined boundary. Confirm whether the price includes garden supplies, outbuildings, alarms, data cabling and specialist systems. Shared building supplies and network-owned equipment should not be silently assumed to form part of the same package.

Our full and partial house rewiring service in London explains how we approach property-wide planning, first fix, second fix and handover.

Not automatically.

An Electrical Installation Condition Report identifies observations and their significance. The findings must then be translated into an appropriate response.

The commonly encountered classifications include:

• C1: danger present, requiring immediate action.
• C2: potentially dangerous, requiring urgent remedial action.
• C3: an improvement is recommended.

A C1 or C2 observation affects the overall assessment, but the code alone does not specify whether the solution is a repair, a circuit replacement or a full rewire.

Electrical Safety First’s guidance also makes clear that a vague recommendation to rewire, without an adequate explanation of the installation’s condition, is insufficient. Electrical Safety First — EICR classification and reporting

Ask the electrician to explain:

1. What was found?
2. Which parts of the installation are affected?
3. What work addresses the finding?
4. Why is the proposed extent appropriate?

A current note about “FI”

In BS 7671:2018+A4:2026, the treatment of FI — further investigation changed. IET explains that FI alone does not produce an unsatisfactory outcome under the updated reporting arrangements. It must not be interpreted as permission to ignore an unresolved safety issue. IET — the change to FI

Rental duties need separate attention. Current GOV.UK guidance requires landlords within the regulations’ scope to complete required remedial or investigative work within 28 days, or a shorter period where specified. The report, its date, applicable requirements and actual findings must be considered together. GOV.UK — electrical safety in rented homes

The following are illustrative examples, not reports of particular PEP projects.

A recently purchased flat with an older fuse box

The buyer intends to repaint, replace carpets and move in. The board looks dated, but there is little reliable information about previous electrical work.

The sensible starting point is to establish the installation’s condition before deciding what to replace.

If the circuits are suitable, a consumer unit upgrade and defined remedial work may be enough. If significant defects are identified, the buyer can address them before investing in finishes that would later need disturbing.

The decision comes from the findings, not the estate agent’s photograph.

A kitchen renovation in a partly modernised house

The new kitchen includes different appliance positions, more lighting and revised controls. Other parts of the house were updated at different times.

This may call for new circuits and targeted replacement, with suitable existing circuits retained elsewhere.

The electrical plan should be coordinated with the kitchen drawings. Agree appliance ratings, connection positions, accessible isolation and lighting arrangements before cabinetry closes off the available routes.

A whole-home refurbishment with widespread electrical alterations

The property is being substantially reconfigured. Existing circuit information is incomplete, several areas show problems and the finished layout will differ considerably.

A comprehensive rewire may offer a clearer project than preserving numerous fragments around the new design.

The quotation should still distinguish renewal required by condition from additions chosen for the finished home. That makes the investment easier to understand and the scope easier to control.

Consumer unit replacement, partial rewiring and full rewiring have different cost structures. Comparing their headline prices without their scope can be misleading.

The important number is the cost of delivering the agreed result, including the work around the electrical installation.

Consumer unit replacement

Check whether the price includes the specified board and protective devices, the necessary assessment, testing, certification and notification.

Also establish how existing defects will be handled. Is identified remedial work included? Will additional fault finding be separately priced? Are access alterations or arrangements involving supply equipment required?

A quotation should make those boundaries visible before the changeover.

Partial rewiring

The number of rooms is only a starting description. Ask which circuits and points are included and how the new work connects with the retained installation.

A small area can still involve awkward routes or considerable access work. Conversely, a well-defined circuit replacement during an open refurbishment may be more straightforward.

Full rewiring

Request a schedule of electrical points and equipment. “Three-bedroom house” does not tell you how many sockets, lighting groups, appliances or control interfaces are being installed.

Confirm the accessory specification too. Standard switches, decorative plates, specialist dimming and architectural lighting requirements are not interchangeable allowances.

Making good needs its own definition

Does the quotation include:

• lifting and reinstating accessible floorboards;
• filling electrical chases;
• plaster repairs or complete skimming;
• decoration;
• removal and reinstatement of fitted joinery;
• repair or replacement of affected floor finishes?

“Making good included” is not sufficiently precise on its own.

NICEIC identifies access, occupancy, the extent of work and chosen upgrades among the factors affecting rewire costs. NICEIC — what influences rewiring costs

At PEP, the useful starting point is an agreed scope and specification. It allows the price to relate to your property rather than an assumed average home.

A consumer unit replacement concentrates much of the physical work around the board, but access elsewhere is still needed for relevant inspection, testing and any agreed repairs. Plan for an electrical shutdown.

Rewiring can involve lifting floors, opening access points and chasing walls. The programme also has to accommodate reinstatement and any work carried out by other trades.

Living in the property

Remaining at home may be possible, but it changes the project.

Discuss safe access, working areas, furniture, children, pets and essential supplies. Working from home through a major rewire requires more planning than simply finding another socket.

NICEIC notes that occupied rewires can take longer and involve additional inconvenience and cost. NICEIC — living in a home during rewiring

Tell the contractor about medical equipment, alarms, refrigeration, home working and other essential requirements before the programme is agreed. Do not assume normal power can be restored everywhere at the end of every working day.

Flats and managed buildings

Confirm access arrangements, working hours, shared-area protection and any permissions required under your lease or building-management procedures.

These are project-specific matters, but resolving them early avoids discovering an access restriction on the day work is due to begin.

In a period property, the shortest cable route may not be the most appropriate one.

Original floors, decorative plasterwork, panelling and other retained features can affect how services are installed. Historic England recommends understanding existing services and minimising permanent damage when planning upgrades. Where relevant, consent requirements should be established before work starts. Historic England — installing electrical and other services

An older house is not automatically listed, and conservation-area status does not make every internal alteration the same type of consent issue.

The practical conversation should focus on the actual building: what must be protected, which routes are available and who is responsible for specialist approvals or reinstatement.

The scope should reflect credible plans for the property, rather than only the equipment connected today.

Tell the electrician about proposed electric cooking, additional bathrooms, heating equipment, electric underfloor heating, EV charging or other significant additions.

A spare slot in a consumer unit does not prove that a new load can be accommodated. The installation’s demand, equipment ratings and supply arrangements still need assessment. Fitting a larger enclosure does not itself increase the incoming electricity supply. IET — assessing additions to a consumer unit

Equipment compatibility matters as well. Protective devices are not interchangeable simply because they appear to fit. The assembly manufacturer’s requirements must be followed. IET — compatibility of devices and components

If the refurbishment includes heating zones, manifold controls or boiler integration, coordinate their wiring requirements during the electrical design. Our guide to smart heating controls for London homes explores that part of the project in more detail.

A well-organised project should leave the homeowner clear about what happens next.

1. Establish the brief.
Explain existing concerns, supply available records and identify planned changes.

2. Assess the installation.
Agree the appropriate inspection or investigation and any access limitations.

3. Define the scope.
Identify retained circuits, replacement work, new additions, protection and responsibilities for associated building work.

4. Agree the programme.
Plan access, shutdowns and the sequence with other trades.

5. Complete the installation.
For a rewire, coordinate the first-fix routes with the finished layout before surfaces are closed. Agree any changes to the original specification.

6. Test and hand over.
Receive the relevant documentation, clear circuit identification and an explanation of the completed work and any remaining recommendations.

Keep the drawings, quotation, certificates and final circuit information together. They will be useful for future maintenance, alterations and property transactions.

The paperwork should match the work undertaken.

Electrical Installation Condition Report — EICR

An EICR records the findings of periodic inspection and testing. It does not, by itself, certify that a proposed rewire or consumer unit replacement has been completed.

Electrical Installation Certificate — EIC

An EIC is used for work including new installations, new circuits and consumer unit replacement. It records the declared extent of the work and is accompanied by the relevant inspection and test information.

Smaller alterations that do not introduce a new circuit may instead be suitable for a Minor Electrical Installation Works Certificate. IET — electrical certification and model forms

Building Regulations documentation

In England, replacing a consumer unit and installing a new circuit are notifiable work. The appropriate notification and certification route must be arranged.

A contractor registered for the relevant competent-person scheme can self-certify eligible work through that scheme. The Building Regulations compliance documentation is distinct from the electrical installation certificate. GOV.UK — Approved Document P

Do not assume that an EIC covering a board replacement means every existing cable has been replaced or that it serves the same purpose as a whole-installation condition report. Read the stated scope.

Which Wiring Regulations edition applies?

At the time this guidance was checked, 2 October 2026, BS 7671:2018+A4:2026 had been published, with the preceding Amendment 3 arrangements remaining valid until 15 October 2026.

The electrician should identify the applicable edition and any relevant transition arrangements for the project. A new edition does not automatically mean every existing home needs rewiring. IET — current Wiring Regulations and transition dates

Before committing, ask:

1. What findings support the recommended scope?
2. Which circuits will remain, and which will be replaced?
3. Are new circuits and replacement circuits clearly distinguished?
4. What protective devices and accessories are specified?
5. Which repairs, access work and finishes are included?
6. What happens if additional defects are discovered?
7. How will shutdowns and essential supplies be managed?
8. Which certificates and Building Regulations records will I receive?

A clear answer to these questions is more useful than a quotation containing only “new fuse box” or “complete rewire”.