Why lightning destroys electronics without hitting the house

01

How does lightning damage a device it never hit?[1]

By induction. A lightning channel carries tens of thousands of amperes that rise and collapse in microseconds, and that changing current creates a changing magnetic field around it. Any loop of wire in that field has a voltage induced across it, which then propagates along the cable into your equipment.

The rate of change is what does the damage rather than the peak current alone. A return stroke can go from zero to peak in a couple of microseconds. Induced voltage scales with how fast the current changes, so lightning's steepness is what makes it dangerous to circuits at a distance where its raw energy is no longer a threat.

Long runs of cable make the problem worse because they enclose more area. Overhead service drops, buried feeds to outbuildings, coaxial runs and phone lines all act as collectors. A detached garage on a long feed is a classic casualty even when the strike landed in a field nearby.

Induced surges are also far more common than direct hits, simply because the area within a few hundred meters of a strike is vastly larger than the strike point. Almost every lightning-related equipment loss is a near miss rather than a hit.

02

What do the surge protector types mean?[1]

They describe where a device installs, not how good it is. Type 1 goes ahead of the main breaker and handles energy arriving from outside. Type 2 installs at the panel and covers the branch circuits. Type 3 is the plug strip at the equipment, rated only for what is left after the first two.

The types are designed to work in sequence. A plug strip alone is being asked to absorb the whole event at the last possible moment, which is why relying only on Type 3 protection disappoints people. Each stage clamps what it can and passes a smaller transient down the line.

Whole-house protection also covers the things you cannot plug into a strip, including the furnace, the well pump, the oven and anything hard-wired.

03

Is a higher joule rating better?

Joule ratings are a poor way to compare devices, and industry standards discourage the comparison. The rating describes total energy absorbed before failure, not how well the device limits voltage during the surge. Let-through voltage and nominal discharge current describe performance far better.

Let-through voltage, published as a voltage protection rating, is the figure that matters to your equipment, because the damage is caused by the voltage that gets past the protector rather than the energy the protector swallowed. A lower let-through voltage means less reaches the device.

Nominal discharge current describes how many surges of a standard test waveform the device survives while continuing to work. That is a durability measure, and it is what separates a protector that keeps working for years from one that quietly dies on its first real event.

Most surge protectors degrade rather than fail loudly. The metal oxide varistors inside wear a little with each event, so a strip that took a hit years ago may be doing nothing now. The indicator light on many units confirms power, not protection.

04

Does unplugging actually work?[2]

Yes, and it remains the only method with no let-through voltage at all. Physically disconnecting power and signal cables removes the path entirely. The catch is that it only helps if you do it before the storm arrives, and it has to include every cable, not only the power lead.

Network and coaxial cables are the ones people forget. A router protected on its power lead and still connected to a buried service line has an unprotected path straight to the board. Damage that enters by the data port and leaves by the power supply is a familiar pattern to anyone who repairs this equipment.

This is also where a live lightning map has a genuinely practical use. Watching strikes appear while a storm is still an hour out gives you the lead time to disconnect deliberately, instead of deciding once thunder is already overhead and the wiring outside is already collecting transients.