Surge Protector vs Extension Lead: What's the Difference and Why It Matters for Your Equipment

Almost everyone has a power strip under the desk with the computer, monitor, router, chargers, a lamp and sometimes even a heater plugged in. Most people call it a "surge protector" and assume their equipment is safe. Very often, though, it's just an ordinary extension lead that protects against nothing — and when overloaded, becomes a hazard in its own right.

An extension lead: just a cable with sockets

An extension lead does one thing: it gives you more sockets where you need them. Inside there's nothing but wires and contacts. Even if the casing has an illuminated switch, it's just a switch. An ordinary extension lead offers no protection against surges, spikes or high-frequency interference.

What's inside a surge protector

A genuine surge protector contains additional components:

• varistors (MOVs) — components that clamp a sudden voltage spike and divert its energy;
• an LC filter — coils and capacitors that suppress high-frequency noise from other appliances on the circuit;
• a circuit breaker — cuts the power in the event of overload or short circuit;
• sometimes indicators showing earthing and protection status.

Side by side

What a surge protector can't do

It's important to understand the limits. A surge protector handles brief spikes — from heavy appliances switching, distant lightning strikes, switching on the grid. It won't protect against sustained overvoltage, such as a "lost neutral" fault in the distribution board, when 300–380 volts can appear at your sockets. Nor does it help with low voltage or power cuts. For those you need a voltage monitoring relay at the flat's supply, stabilisers and a UPS. Varistors also wear out: after several strong surges they lose their protective ability, while the strip carries on working as a plain extension lead.

The danger of overloaded extension leads

Every extension lead and surge protector is rated for a certain current — usually 10 or 16 amps, or 2.2–3.5 kW. The thin wires in cheap models can handle less in practice. Plug a heater, a kettle and a computer into one strip and the wires and contacts heat up, plastic melts and contacts scorch — a genuine cause of fires. Daisy-chaining extension leads one into another is particularly dangerous.

How to spot a poor-quality protector

• very light weight and a thin cable;
• no maximum current or power rating, or unrealistic figures;
• no earth contacts in the sockets, or they aren't connected;
• plugs sit loosely and wobble;
• the casing gets warm at moderate load or smells of plastic;
• no information on maximum surge energy absorption.

How to plug in your equipment

1. Computer, monitor and network equipment through a quality surge protector or UPS.
2. High-power appliances — heaters, kettles, irons, air conditioners — straight into a wall socket, not the strip with your electronics.
3. Never daisy-chain extension leads.
4. Don't hide power strips under rugs or in enclosed spaces where they can't cool.
5. Make sure the wall socket has a working earth.
6. Replace the surge protector after a storm with heavy surges, or every few years.

A real example

In a flat in Gldani, the router, monitor and laptop charger all died at once after a thunderstorm. Everything was plugged into a cheap strip with a switch that the owners believed was a surge protector. Opening it up showed there wasn't a single protective component inside. We replaced the damaged equipment, fitted a quality surge protector and a UPS for the computer and router, and an electrician installed a voltage relay in the distribution board.

A word about earthing. The varistors in a surge protector dump the surge energy into the protective earth conductor. If the socket has no earth — which is very common in older Tbilisi buildings — the protector's effectiveness drops sharply: part of the protection simply doesn't work. What's more, in some unearthed setups an unpleasant voltage can appear on equipment casings — you feel a slight tingle touching the metal parts of a computer or a charging laptop. So before choosing protection, check your sockets: do they have an earth contact, and is it actually connected rather than just present in the socket housing? An electrician can check this with a tester in a few minutes. If there's no earth, adding one is the first investment that makes all your other protection meaningful. It's also worth knowing that surge protectors don't last forever: quality models have an indicator that goes out when the protective components are exhausted, which is your signal to replace the unit.

Let us protect your equipment

We work across Tbilisi around the clock, choosing surge protectors and UPS units and checking sockets and earthing. Learn more on our electrician, 24/7 computer help and router repair pages.