What changed in April 2026
The wiring regulations were updated this year. BS 7671:2018+A4:2026, the Amendment 4 edition, was published on 15 April 2026, and the version before it is withdrawn six months later in the middle of October. Any board going in now is wired and certified to the new book.
The change that matters most in a board swap is a new requirement for 30mA RCD protection on the final circuits feeding your light fittings. Sockets, and cables buried in walls, have needed that protection for years. Domestic lighting did not, and now it does.
On a modern installation that is a non-event. In an older house it is the single biggest reason a board change turns out to be a longer job than the quote assumed, for reasons worth spelling out properly below.
One practical upshot while the two editions overlap: from the middle of October the older edition can no longer be used. If you are comparing quotes right now, it is a fair question to ask which edition the installer intends to certify your job to.
Why a new board sometimes trips when the old one never did
Here is the part nobody warns people about, and it is the reason we test before we price.
An old board with rewireable fuses, or with plain breakers and no RCD, is not watching for current leaking to earth. A modern one, with protection on every circuit, is watching constantly. Fit that to an older installation and it will report every bit of leakage that has been quietly accumulating for the last thirty years.
A small amount of leakage is normal, and it stacks up: an immersion heater element on its way out, an ageing cooker, outdoor lights on a cable that has taken in water, a damp garage, an old chest freezer. Individually, none of it would trip anything. Added together on one device, it is more than enough.
Now put the new lighting requirement on top and you get the fault we expect to meet all over the older housing around Rotherham and the Dearne Valley: the borrowed neutral. In a great many houses wired between the 1960s and the 1980s, the upstairs and downstairs lighting share a neutral somewhere, usually at a landing switch or a ceiling rose.
Nobody ever noticed, because nothing was watching. Separate those circuits onto their own protection, which is now what the regulations ask for, and the board drops out the moment somebody turns a light on.
That fault was already in your house. The new board did not create it, it exposed it. It does still have to be traced and put right before the installation can be certified, which is exactly why a price given over the phone, sight unseen, is a guess rather than a quote.
Which board actually suits your house
There is a real choice here, and it is worth understanding rather than leaving to whoever turns up.
The cheaper arrangement splits the house across two shared RCDs. It meets the standard, but it has an obvious weakness: one fault takes out everything sitting behind that device, so a failing freezer in the garage can put half the house in darkness while you are out.
The alternative gives every circuit its own individual protection, so a fault isolates itself to the one circuit it belongs to and the rest of the house carries on. Given how much leakage an older installation tends to carry, that is what we normally fit.
The other decision is how much room to leave. A board that is exactly full on the day it goes in means the next thing you add, whether that is a car charger, a shower or a garden supply, needs the box opening up again.
Your earthing arrangement matters too, and it is not something you can tell from the front of the board. Most homes take an earth from the incoming supply.
Some, particularly older or more isolated properties, have no supply earth at all and rely on an earth rod in the ground instead. Those installations behave differently under fault conditions and need the board arranged to suit. Establishing which one you have is part of testing, not guesswork.
Where the board lives, and moving it
Plenty of boards are in daft places: the back of an under-stairs cupboard behind the hoover, high on a cellar head where you need a stool, or boxed in when a kitchen was fitted around them. A board you cannot reach is a board you cannot switch off in a hurry.
Relocating one during the change is often straightforward and is much cheaper done then than as its own job later. What governs it is the run between your meter and the board. Keep it short and it is simple work.
Move the board a long way from the meter and the connection between the two needs protecting in its own right, which adds a component and a bit of cost. Anything involving the sealed cut-out ahead of your meter has to go through the network operator rather than us, so we will tell you early if your plan needs them involved.
If a kitchen refit or an extension is coming, that is the moment to move it. The wall is open anyway.
Landlords, HMOs and commercial boards
Not every board is a domestic consumer unit under the stairs.
If you let a house in multiple occupation, purpose-built student accommodation or a care home, the bar is higher than for an ordinary family home: arc fault detection is required on socket circuits up to 32A in those premises, rather than being the recommendation it is in a single household. It tends to surface late, at an inspection or a licensing visit, when it is least convenient.
On the commercial side we replace and extend three-phase distribution boards, sub-mains and panel boards in units, shops and workshops. That work gets planned around trading hours instead of through them, and it usually has to be staged so part of the building stays live while the rest is changed over.
Worth noting for anyone reading this with a commercial property: the new lighting rule described above applies to domestic premises, so it does not land on your distribution board, although the rest of the amendment does.
Either way the paperwork is the point of the exercise, and the testing and inspection side of it is what most landlords and managing agents actually come to us for.
What does a fuse board replacement cost, and how is it quoted?
You will not find a single number on this page, because the box itself is the cheap part. The variable is what the testing finds behind it.
That is why a board change with us starts by establishing the condition of what is already there. It is the only honest way to quote the real job rather than the optimistic one. Typical market figures for a domestic board, along with the signs that yours is due, are set out in our guide to whether you need a new fuse board.
Whoever you use, two things belong in the quote: the testing and certification as well as the swap itself, and a clear position on what happens to the price if a pre-existing fault comes to light. Get both in writing and you can compare quotes properly.