Fuse box and consumer unit replacement in London

Approved Document P lists replacing a consumer unit as notifiable work in a home in England. There are two legal routes. An electrician registered with a competent person scheme can self certify the work. Otherwise the council's building control must be told before work starts, and will inspect it. The Planning Portal recommends using a registered installer. Ask to see their registration and check it on the scheme's online register.

The work itself must meet BS 7671, the wiring regulations. Since 15 October 2026 the only current version is BS 7671:2018+A4:2026, known as Amendment 4, according to NICEIC's summary. New boards in homes are fitted in a non combustible enclosure, which in practice means metal.

Old fuse boxes protect against overload but cannot detect current leaking to earth. A new board with RCD protection can. In a house where cables have been added over decades, with a borrowed neutral here or a damp outside light there, the new board can start tripping on day one.

Testing the circuits first means these faults are found and priced up front. It also shows whether the earthing is good enough and whether the meter tails, the cables from the meter to the board, are big enough for the new board.

The Valuation Office Agency counts 52% of Harrow's homes and 41% of Sutton's as built between 1919 and 1939, and 35% of Havering's from 1945 to 1972. Many of these homes were rewired in the 1960s or 70s and still have the fuse box from that rewire. Wire fuses, a wooden back board and no RCD are common signs.

In converted flats, common across Wandsworth and Hackney, the consumer unit may be squeezed into a hall cupboard by the front door with the meter in a communal cupboard downstairs. That affects how the new board is fitted and whether the meter tails need replacing.

A split board uses two RCDs, each covering several circuits. An RCBO board gives each circuit its own protection, so one fault only knocks out one circuit. Under Amendment 4, arc fault detection devices (AFDDs) are required on socket circuits in houses in multiple occupation, high rise residential buildings over 18 metres or six storeys, care homes and student accommodation, and recommended elsewhere. The survey will explain which suits your home.

The power to the whole home is off for most of the job, so plan for no heating controls, no fridge and no internet for the day. Freezers kept shut usually hold their temperature for some hours. If someone at home relies on powered medical equipment, say so when you book.

In a flat, the electrician may need access to the meter cupboard in the communal hall, and sometimes the managing agent has the key. If the meter tails are too small or the main fuse needs changing, the network operator may need to visit first. That is arranged through your supplier or by calling the network operator, and you are told before the job is booked.

At the end you should get an Electrical Installation Certificate with a schedule of test results for every circuit, a labelled board, and notice that the work has been registered under the building regulations. Keep these with your house papers. You will need them when you sell, and a landlord will need them alongside the next EICR. Our post on what changes the cost of a new consumer unit explains what is priced in and what is extra.