Surge protected, stabilised or on a UPS: which box saves the TV, and which is a placebo

Three boxes, one wall socket: the surge strip, the "voltage stabiliser" and the UPS all promise protection, all cost different money, and they defend against three different attacks. Buying the wrong one is how a lightning season becomes a dead TV with a healthy-looking fuse inside a protector.

The three threats, named

• The spike: microseconds of over-voltage - lightning nearby, a transformer switching, the grid's own thunder. What kills electronics.
• The brown-out: sustained under-voltage - long harmattan-season sag while the compressor works harder and the PSU cooks. What ages electronics.
• The black-out: the zero that cuts mid-cycle, corrupts the file, drops the router, and ends the UPS conversation.

Which box does which job

The surge strip exists for one thing: the spike, absorbed by a metal-oxide varistor whose entire spec is "clamps at what voltage, and for how many joules." A MOV-rated strip with a real joule figure protects; a socket with a red light and a moulded shell is a power strip with anxiety relief bolted on. The honest test - the little "protected" lamp tells you the MOV is alive, and when it goes dark the strip is now ordinary - is the only maintenance this device asks, and it is why the indicator is not decorative.

The relay-type "stabiliser" box handles the brown-out: it watches the line and switches taps inside a transformer to keep the output near nominal - with a visible, audible clunk, and a fraction-of-a-second of dropout per correction that modern switching supplies shrug off. It does nothing for a lightning spike beyond surviving it itself - the clunky box is the reason the TV still runs at 190 volts, and the reason the same TV still dies when the sky fires.

The UPS is the only one that answers all three: battery-backed online or line-interactive boxes ride through the blackout, and a decent one filters spikes and sags on the way in. Its costs are the honest ones: the battery is a consumable on a two-to-four-year life in a warm room, and a "TV and decoder" line-interactive unit buys an orderly shutdown, not a movie marathon.

What no box fixes: the earth

Surge devices work by dumping energy to earth - and a Nigerian socket with an earth pin connected to nothing makes every protector in the house an expensive suggestion. If you buy one serious protection habit, it is this one: an electrician confirms the earth at the board and the socket you care about, because no clamp voltage survives the missing copper to the ground rod. Read the desk's wiring red-flags article for the visible signs that your earth is decorative before spending a kobo on boxes.

The verdict, as a rule

TV, decoder and console: a rated MOV strip with the indicator, on an earthed socket. A PC and router that cannot survive a mid-save blackout: a line-interactive UPS - the one appliance where the box earns its battery. A fridge or AC in a sago district: a motor-rated stabiliser, and nothing else near it. The grid will not tell you which night it brings which threat; the three boxes above are how you stop asking it.