The Best Whole House Surge Protector UK (2026): Which Consumer Unit SPD to Fit

Surge damage in a British home rarely looks dramatic. It looks like a boiler PCB that dies during a storm three streets away, a router that will not hold a connection afterwards, or a heat pump inverter board failing eighteen months into a ten-year warranty. The cause is a transient overvoltage of a few hundred to a few thousand volts lasting microseconds: too brief for an MCB or RCD to react to, and too large for a £15 plug-in block to absorb.

Since Amendment 2 to BS 7671 in 2022, a surge protection device (SPD) is effectively the default in new domestic installations and consumer unit replacements unless the electrician documents a risk assessment saying otherwise. That has pushed homeowners into buying kit they do not understand at prices varying tenfold. Here is what we would specify, what it honestly costs, and where the money goes.

Exposure is not spread evenly. Transients ride in on the incoming supply, and the biggest variable is whether your service is overhead or underground. A village property fed by poles takes hits an inner-city flat never sees.

If your board is still a rewireable fuse box or a 1990s plastic unit, an SPD is the wrong first purchase. Read the signs your electrical panel needs an upgrade first, because surge protection bolted onto a board with no RCD coverage is money spent in the wrong order.

• •Strong case: an overhead supply, a rural location, or a building with a structural lightning protection system.
• •Strong case: a heat pump, solar PV with battery storage, or an EV charger. Inverter and control boards are the most surge-sensitive parts of a modern house and cost £400 to £1,200 each to replace.
• •Weak case: an urban flat on an underground network with a laptop, a television and a couple of tablets. The arithmetic does not work, and BS 7671 allows a documented risk assessment to record that.
• •No case at all for plug-in strips alone: they clamp late and do nothing for the hardwired boiler, shower or oven.

We are open about method: we do not fire 8/20 microsecond impulses at these devices, and no consumer publication credibly does. We read declared performance to BS EN 61643-11 and compare it with what we find degraded or failed inside real consumer units during periodic inspection.

• •Up, the voltage protection level, is the number that matters: domestic kit tolerates roughly 1.5 kV, so we want 1.2 to 1.4 kV. In of 20 kA with Imax of 40 kA is the sensible discharge band.
• •Type 2 covers almost every UK house. Type 1, or combined 1+2, is for buildings with lightning protection. Type 3 is point-of-use only and must sit downstream of a Type 2.
• •A replaceable cartridge matters, because the varistors inside are sacrificial and a £35 cartridge beats a £95 whole-unit swap.
• •Status indication, ideally a remote signalling contact, since a spent SPD fails silently. Mixing brands inside a type-tested board is also a real warranty argument.

Four devices cover the realistic spread of UK homes. Prices below are for the device alone; installation is broken down next.

One warning applies to all four: the conductors between the SPD and the live and earth terminals must be as short as physically possible. BS 7671 asks for a total lead length under 0.5 m for a hard reason: an 8/20 microsecond impulse adds roughly 1 kV per metre of lead. Fit a 1.2 kV device on 700 mm of tail and you have turned it into a 1.9 kV device.

Materials are the smaller half of this job, which is why device price alone is a poor guide to what you will pay.

If the board is being replaced anyway the SPD is nearly free in relative terms, adding £80 to £140 to a consumer unit change that runs £550 to £950 for a three-bedroom semi. For the wider picture see what a consumer unit upgrade costs and current electrician rates by job.

• •SPD device: £30-£45 budget Type 2, £70-£95 mid-range, £130-£180 premium, £180-£320 for Type 1+2.
• •Backup overcurrent protection: a 40A or 63A Type C MCB at £8-£16, unless the board is SPD-ready with a protected way already fitted.
• •Sundries, labour and paperwork: £8-£15 of earth conductor and fixings; one to one and a half hours at £45-£75 an hour plus a £40-£90 minimum charge; and a Minor Electrical Installation Works Certificate at £0-£40.
• •Worked example one, modern SPD-ready board with a spare way: device £75, sundries £10, one hour labour £65. Around £150 all in, common in post-2019 installations.
• •Worked example two, serviceable board with no spare way: device £75, four-way surge enclosure £55, Henley block £18, sundries £15, two and a half hours labour £165. Around £330.
• •Worked example three, rural TT installation on an overhead supply with Type 1+2: device £245, 16 mm squared earth run £30, enclosure £60, three and a half hours £245. Around £580, the top of a legitimate range rather than a rip-off.

Adding an SPD to an existing consumer unit is minor works in England and Wales and is not notifiable, whereas replacing the board is. Scotland and Northern Ireland run different regimes, and when electrical work needs sign-off sets out the boundary.

• •A quote that does not name the device Type and its Up rating cannot be compared. Ask for both in writing.
• •It should state your earthing arrangement: TN-S, TN-C-S (PME) or TT. A TT installation needs a different SPD configuration, and an electrician who has not checked has not surveyed.
• •Under £100 fitted and all-in is suspicious. Something is missing, usually the certificate, the backup device or the survey time.
• •Over £400 for a straight retrofit into a modern board needs justifying. Only enclosure work, a long earth run or restricted access defends it.

• •Buying the device online and expecting an electrician to fit it. Many refuse, and those who agree will not warrant the part.
• •Specifying Type 1 without a lightning protection system. It is overkill, demands a heavier earth conductor, and buys nothing on an underground supply.
• •Assuming one Type 2 protects everything equally. Past roughly ten metres of cable the let-through voltage climbs, so sensitive kit still wants a Type 3 at the socket.
• •Fitting it and forgetting it. Check the status window twice a year and after any storm that took the lights out, which belongs on your power outage checklist.

Fitting an SPD means working inside a live consumer unit or arranging isolation at the cut-out, and the cut-out fuse belongs to the network operator, not to you. That puts it among the electrical repairs you should never DIY. A misconfigured SPD on a TT system can also hold the installation at fault voltage. Use an electrician registered with NICEIC, NAPIT or ELECSA, insist on the certificate, and keep it: it is the first thing an insurer asks for after surge damage.