What Is Involved in Replacing a Consumer Unit in Stevenage?
A consumer unit replacement is one of the most common electrical jobs carried out across Stevenage — and one of the most frequently misunderstood in terms of what it actually involves. Most homeowners know it means getting a new fuse board fitted, but the process that surrounds that — the assessment, the testing, the regulatory requirements and what happens after the work is complete — is less well understood.
This matters because a consumer unit replacement is not a minor task that can be approached casually. It is notifiable work under Part P of the Building Regulations, it involves disconnecting and reconnecting the incoming electricity supply, and it requires proper testing before the installation can be certified as safe. Getting it done correctly, by a registered electrician who understands what the job involves, is the difference between an installation that is legally compliant and documented, and one that is not — with all the implications for safety, insurance and property sale that follow.
Stevenage’s housing stock makes this a particularly relevant question. The town’s new town development programme produced the majority of its residential areas between the early 1950s and the 1970s — estates across Bedwell, Shephall, Pin Green, Chells and Symonds Green were built rapidly and at scale during this period. Many of these properties now have electrical installations that are approaching 60 to 70 years old, with consumer units that were never designed to meet current protection standards. Understanding what a replacement involves is the first step to getting it done.
Why Consumer Units Need Replacing
Before walking through the process, it is worth understanding what a consumer unit actually does and why older ones become inadequate over time.
The consumer unit — commonly called the fuse board or fuse box — is the central hub of the electrical installation. It receives the incoming supply from the meter, distributes it to individual circuits throughout the property, and provides protection against electrical faults through fuses, MCBs (miniature circuit breakers), RCDs (residual current devices) and RCBOs (residual current breakers with overload protection).
Older consumer units — the rewireable fuse boards common in properties built before the 1970s, and the early MCB boards that followed through the 1980s — do not provide the level of protection required by current wiring regulations. A rewireable fuse board offers no protection against electric shock at all — it only responds to overload or short circuit conditions, not the type of earth fault that causes fatal shocks. A modern consumer unit with RCD or RCBO protection responds to earth faults in milliseconds, cutting the supply before a serious injury can occur.
Since 2016, all new consumer unit installations in domestic properties are also required to use metal-encased units rather than plastic — a fire safety requirement that contains any arc fault within the unit rather than allowing it to spread to surrounding materials.
Step One — Assessment of the Existing Installation
A consumer unit replacement does not begin with removing the old board. It begins with the electrician assessing the existing installation to establish what is there and what condition it is in.
This matters for two reasons. First, a consumer unit replacement is only appropriate where the cables connected to it are in satisfactory condition — if the wiring throughout the property is deteriorated, incorrectly sized or of a type that is no longer acceptable under current regulations, replacing the board without addressing the wiring does not solve the underlying problem. Second, the assessment determines what the new consumer unit needs to accommodate — how many circuits, what protective devices are appropriate for each, and whether any additional work is required alongside the board replacement itself.
For Stevenage’s new town housing, this assessment often reveals a consistent picture — original installations from the 1950s and 1960s that have been partially updated at various points without ever being comprehensively reviewed. Rubber-insulated wiring from the original installation, later PVC cables added for additional circuits, and non-standard modifications that have accumulated over the decades. An electrician who carries out a proper assessment before quoting will identify what can be retained and what needs addressing alongside the board replacement.
In some cases, the assessment will indicate that a full rewire is more appropriate than a consumer unit upgrade alone — where the wiring is too deteriorated or non-compliant to justify connecting it to a new board. An honest electrician will tell you this rather than simply replacing the board and leaving the underlying installation unaddressed.
Step Two — Agreeing the Scope and Specification
Once the assessment is complete, the electrician will confirm what the replacement involves — the type and specification of the new consumer unit, any additional work required such as bonding upgrades or tails replacement, and the final price.
The two main consumer unit types for domestic installations are the split-load unit — where circuits are divided between two RCD-protected sections — and the full RCBO board, where every individual circuit has its own combined MCB and RCD protection. The full RCBO board is increasingly the preferred specification for new installations because a fault on one circuit trips only that circuit rather than the entire half of the board. The difference in cost between the two types is modest, and for most Stevenage homeowners the RCBO specification is worth the marginal additional price.
The specification discussion should also cover the number of ways required — how many circuits the new board needs to accommodate, including any spare capacity for future additions such as an EV charger or additional circuit.
Step Three — Preparation and Isolation
On the day of the work, the electrician begins by isolating the incoming supply at the meter. This requires liaison with the Distribution Network Operator in some cases, particularly where the meter tails — the cables between the meter and the consumer unit — also need to be replaced or repositioned. In most standard residential installations, the isolation is straightforward, but it is worth confirming this at the assessment stage so there are no surprises on the day.
Once the supply is isolated, the property is without power throughout the working day. This is unavoidable — the existing board needs to be fully de-energised before any work begins. Planning around this in advance — ensuring food that needs refrigeration is managed, that work-from-home arrangements are adjusted, and that any time-sensitive power requirements are addressed — makes the day considerably less disruptive.
Step Four — Removal of the Old Unit and Installation of the New
With the supply isolated, the old consumer unit is disconnected and removed. Each circuit cable is carefully identified, labelled if not already clearly marked, and checked before being connected to the new board. The new metal consumer unit is mounted, the circuits are connected to their appropriate protective devices, and the earthing and bonding arrangements are checked and updated where necessary.
For properties in Stevenage’s new town estates, the earthing arrangements from the original installation sometimes need attention at this stage. Older properties may have inadequate main protective bonding to gas and water services, or earth connections that do not meet current standards. Addressing these as part of the consumer unit replacement is both good practice and a regulatory requirement.
Step Five — Testing
Testing is the stage that transforms a connected installation into a certified one — and it is not something that can be skipped or abbreviated. Once the new board is installed and all connections are made, the electrician carries out a full series of tests on every circuit.
The tests include continuity of the protective conductors, insulation resistance of each circuit, verification of polarity, earth fault loop impedance, and RCD or RCBO response time testing. Each test confirms a specific aspect of the installation’s safety and performance. The results are recorded on the test schedule that accompanies the installation certificate.
For a standard Stevenage property with eight to twelve circuits, the testing process typically takes one to two hours. The time cannot be meaningfully reduced without compromising the thoroughness of the assessment.
Step Six — Certification and Notification
On satisfactory completion of testing, the electrician issues an Electrical Installation Certificate. This is a legal document under Part P of the Building Regulations confirming that the installation has been designed, constructed and tested to the standard set out in BS 7671. It includes the test results for every circuit, the specification of the new consumer unit, and the details of the registered electrician who carried out and certified the work.
A scheme-registered electrician — a member of NICEIC, NAPIT, ELECSA or an equivalent government-approved competent person scheme — self-certifies the work and notifies building control on your behalf. You do not need to make a separate application or arrange an independent inspection. The certificate and the building control notification together provide the complete documentation trail that confirms the work is legally compliant.
This documentation matters when you come to sell the property — a buyer’s solicitor will ask for evidence that electrical work has been carried out to the required standard, and an Electrical Installation Certificate is the correct document to provide.
How Long Does a Consumer Unit Replacement Take in Stevenage?
For a standard Stevenage property, the full process on the day — isolation, removal of the old board, installation of the new unit, testing and certification — typically takes four to eight hours depending on the number of circuits and whether any additional work is required alongside the board replacement. Most consumer unit replacements are completed within a single working day.
The assessment visit before the work is carried out is typically a separate, shorter appointment — usually thirty minutes to an hour depending on the size of the property and the complexity of the existing installation.
Getting a Consumer Unit Replaced in Stevenage
If you are based in Stevenage, Knebworth, Letchworth, Hitchin, Welwyn or anywhere across Hertfordshire, get in touch and we will arrange an assessment visit. We will tell you clearly what the installation needs and give you a straightforward quote for the work. No obligation and no pressure.