What a consumer unit actually does
The consumer unit distributes the electrical supply to the circuits in a home and contains devices intended to protect cables and people when abnormal conditions occur. It is one part of the installation; it cannot compensate for every defect in the connected wiring.
Older equipment is not automatically unsafe, but limited protection, damage, poor alterations, lack of capacity or unsatisfactory test results can make an upgrade appropriate.
Reasons to review an older fuse board
- Rewireable fuses or limited residual-current protection.
- Visible damage, overheating, loose covers or missing blanks.
- Poor circuit identification or multiple unsafe additions.
- Insufficient space for planned circuits.
- Repeated tripping that requires proper diagnosis.
- A condition report that recommends distribution or protection improvements.
A plastic enclosure alone does not prove a board is dangerous, and a new metal enclosure alone does not prove the connected circuits are sound. The decision should be based on the whole installation.
Checks before a board change
Pre-change testing helps establish whether the circuits are suitable to reconnect to modern protective devices. It can identify insulation problems, borrowed neutrals, poor earthing, incorrect polarity or circuit-identification issues before the planned shutdown.
The supply arrangement, main protective device, tails, earthing and bonding also need consideration. Where another party controls the meter or service equipment, their involvement may be needed.
Understanding common device options
RCBO protection
An RCBO combines overcurrent and residual-current protection for an individual circuit. This can improve fault separation because a problem on one circuit is less likely to disconnect unrelated circuits.
Surge protection
A surge protective device is intended to limit certain transient overvoltages. Its selection and installation should follow the design assessment and current requirements rather than being treated as a decorative extra.
Other protective measures
Some installations or circuit types may require further protective-device considerations. The correct arrangement depends on the property, risks and design; it should not be selected from an online package name alone.
What happens on installation day
- The supply and circuits are safely isolated.
- The old equipment is removed and the new enclosure and devices are installed.
- Circuits are terminated, identified and labelled.
- Electrical testing is completed before circuits are returned to service.
- Any unexpected defects are explained and made safe.
- The agreed documentation and notification route are completed.
Power will be unavailable for a period. Sensitive equipment should be shut down, and anyone working from home should plan for the interruption.
Why unexpected faults sometimes appear
Modern residual-current devices can expose leakage or connection problems that older arrangements did not reveal. This does not mean the new board created the defect; it may mean the connected circuit now needs attention before it can be safely returned to service.
A professional quotation should explain how initial testing and unforeseen remedials will be handled. Unlimited hidden repair work should not be silently assumed in a fixed price.
Part P and paperwork in England
Electrical work in dwellings is subject to Building Regulations. Replacement consumer units, new circuits and certain work in special locations are among the matters that may require notification. The compliance route should be agreed before work begins.
The current official reference is Approved Document P on GOV.UK. The electrical certificate and any Building Regulations compliance record serve different purposes, so retain both where applicable.
Questions to ask about the quotation
- What board and protective-device arrangement is proposed?
- Is surge protection included or assessed?
- What pre-testing is included?
- How will existing circuit defects be handled?
- Are earthing or bonding upgrades included?
- What electrical certificate and notification route will be provided?
- Who is responsible for meter seals or supply isolation if required?
What affects the cost
Cost depends on circuit count, board specification, access, pre-test results, earthing work, enclosure changes and the time required to identify circuits. A headline price based only on the number of ways may not include the condition of the installation.
See the Bastian Electrical domestic price guide for an example planning range, then request a property-specific quotation.
The next step
Send a clear photograph of the existing consumer unit with the cover closed, the property type, any known faults and the reason for the upgrade. Do not remove covers to take photos.