When to replace an old Fusebox with a Consumer Unit

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(Photo: An old fuse box that should be replaced)

An old fuse box should be replaced as soon as possible. If you still have an electrical panel / mains box / fuse box that contains fuses or fuse wire in 2025 then this is likely to be several decades old already and should be replaced. If you have a consumer unit (a more modern fuse box) that is 30 - 40 years old, then this should also be replaced as it is likely that the electrical components are no longer guaranteed to function correctly or safely. 

1) What does the electrical system do?

The electrical system in our homes is one of the most important systems for ensuring that everything works. Without a functioning and safe electrical system, your gas heating system may also break down and refuse to work. Despite this, many of us take for granted the electrical needs of our modern homes and assume that, if everything is working then all must be ok and in good condition?

The electrical system is responsible for delivering power to our socket outlets, lights, switches and other electrical equipment around the home. Without the electrical system we would have very dull and complicated lives indeed. Imagine no Wi-Fi, no heating, no lights and no ability to keep food cold or cook!!

2) What does the fuse box or consumer unit do?

(Photo: A modern RCBO consumer unit)

The "brains" of the electrical system is the large unit that contains fuses, trip switches and other electrical devices. This unit is referred to by many names including circuit breaker panel, mains electric box, fuse box, consumer unit, distribution board or electric panel. The correct name in 2025 is consumer unit (UK) and modern consumer units have the most up to date technology installed to prevent damage to our appliances, cabling and electrical accessories. The modern consumer unit also offers a great deal of protection against electric shock when compared to older fuse boxes. 

The job of the fuse box or consumer is to 'watch over' our electrical circuits, prevent overload, electric shock and surges. It also divides the electrical system into circuits to allow smaller cables to be used around the installation for each purpose. You can find out what parts are inside a consumer unit and their purpose in our article here. 

3) How long does a fuse box or consumer unit last?

Old fuse wire fuse boxes can last a long time as there are very few moving parts that need to be replaced with the exception of the Main Switch. Some older fuse boxes are still in use today and I have seen units over 50 years old still functioning. The switchgear of modern consumer units will last up to 30 years if properly maintained and installed. The issue with older fuse box technology is that it no longer offers acceptable protection against electric shock and should be upgraded to ensure that modern safety standards are met. Old consumer units (with trip switches) should be periodically inspected and replaced when needed.

(Photo: A small fire requiring complete replacement of the consumer unit)

In some cases, the life of a consumer unit or fuse box can be dramatically shortened without inspections and fires can result internally requiring the unit to be replaced. 

4) Is it a legal requirement to have a New Consumer Unit?

In some cases, YES although if you have an old consumer unit or an old fuse box you are not breaking the law. If for instance you were to have the property rewired then a new compliant consumer unit would have to be installed to meet regulations. If you were to have a new electrical circuit added (EV charger, garden shed supply etc) then in some cases the old box or unit would have to be replaced in order to satisfy regulations. 

Where a rented property fails an electrical inspection due to an old or damaged fuse box, this would have to be replaced in order to make the properties electrical system compliant. 

Where additions or alterations are carried out on wiring systems, we have to ensure that the current standards for electrical safety are met before the alterations or additions can go ahead. 

5) ​When are newer consumer units required?

One of the main reasons a consumer unit replacement (or board change) is carried out is due to the addition of extra electrical circuits. Each consumer unit has a maximum number of circuits that it can safely supply and once the limit is reached a larger consumer unit may be required in order to install additional electrical equipment and circuits. An older fuse board will likely have no extra room to add additional circuits and in many cases, due to the age of fuse boards, the protection offered would not meet modern standards anyway. 

(Photo: A modern consumer unit with NO space remaining)

Adding extra circuits to an older fuse box with no room can mean electrical circuit overload on wiring, fuses or circuit breakers. An overloaded fuse box can be dangerous and presents a risk of fire or damage to internal components of the fuse box. 

6) What is RCD Protection?

RCD protection is the addition of a Residual Current Device, normally to offer protection against electric shock. An old fuse board will not have RCD protection on some or all of the circuits and as such, a fuse box replacement is often necessary to upgrade the electrical system. An RCD detects earth leakage and switches off individual circuits or groups of circuits to prevent electrical shock. Earth leakage is a situation where electrical current is missing from a circuit as would be the case if you were receiving an electric shock. The earth leakage device (RCD) detects this missing current and trips off to prevent harm. 

(Photo: An older RCD switch)

7) What type of consumer unit do I need?

​We have written a special article to answer this question. Generally speaking, in 2025, you would want an RCBO consumer unit with surge protection to protect against the following:

• Electrical Faults
• Power Surges
• Arcing
• Fatal Electric Shock
• Short Circuit
• Electrical Overload

​There are many different types of consumer unit, manufacturer brands and models on the market but your electrician is the best person to advise on the type of replacement that will work best in your home. 

8) Will a new consumer unit work with old wiring?

​This is a valid concern for many homeowners and consulting a qualified electrician is best to answer your questions. We have written an article that covers the risks of installing a new consumer unit on old wiring which you should find helpful. The best way of establishing if a new consumer unit will work effectively with your wiring system is to have a professional electrician carry out a periodic electrical inspection. 

(Photo: Old Fuse Box with old Vulcanised Indian Rubber (VIR) wiring throughout)

The electrical inspection produces a document called and electrical installation condition report which will detail the condition of the system, any faults and recommendations for improvements. At this point, you will be able to determine if your wiring needs to be replaced or if a new consumer unit will suffice. Some faulty wiring can be repaired or replaced if there are only minor issues so try not to worry until the inspection has been carried out and the condition of your electrical system established. 

9) Conclusion

Rewireable fuses and cartridge fuse boxes should now be replaced for a safety regulations compliant consumer unit. The existing installation should be tested to ensure there is no additional work required to remedy any electrical problems before the new unit is installed. Whilst the initial outlay of a replacement consumer unit can seem expensive, the longevity of modern circuit breakers, RCDs and RCBOs means that a new unit is a great long term investment.