The cost of a fuse board or consumer unit replacement depends on factors specific to each installation, which is why an on-site assessment is needed before a cost can be confirmed. Understanding what influences the scope helps customers know what to expect when an engineer visits.
The number of circuits is one of the main factors. A larger property with more circuits requires a consumer unit with more ways (individual circuit positions), and correctly connecting and testing each circuit takes additional time.
The condition of the existing wiring also matters: if circuits have faults, deteriorated insulation or do not achieve the required test values, these issues need to be addressed before the new unit can be safely connected. Identifying such conditions at the assessment stage, rather than during the job, allows for more accurate scoping.
Current BS 7671 requirements for new domestic consumer units call for non-combustible construction or a suitable non-combustible enclosure, typically metal. An existing plastic unit does not automatically need replacing solely because of its enclosure material; its condition, protection and suitability should be assessed.
If your property has an older plastic unit with rewirable fuses or early miniature circuit breakers (MCBs) without residual current device (RCD) protection, a replacement brings the installation closer to the current standard. A consumer unit replacement is notifiable work under Part P of the Building Regulations.
When carried out by a registered competent person, the electrician self-certifies the work and issues both an Electrical Installation Certificate and the Building Regulations compliance documentation. Both documents should be kept, as they form part of the property record and are commonly requested during conveyancing.
The earthing arrangement and incoming supply capacity are checked as part of the assessment. If either requires attention, the engineer will explain what is involved before any work is agreed.