What a surge is
A surge – or transient overvoltage – is a very brief spike in voltage. Lightning strikes near power lines can cause them, but so can everyday switching on the network or large equipment turning on and off. Most last for a tiny fraction of a second, but they can damage sensitive electronics.
What an SPD does
A surge protection device sits in or next to your consumer unit and diverts excess voltage safely to earth. It protects the fixed installation and, to a degree, the things plugged into it – TVs, computers, routers, smart appliances and EV chargers all contain delicate electronics.
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Why they're now so common
Current wiring regulations call for surge protection in most new installations and consumer unit replacements unless a risk assessment shows it isn't needed. That's why you'll see SPDs on many quotes for new boards.
If you're not having any work done, there's generally no requirement to add one, but it can be worth discussing next time your consumer unit is upgraded.
