How to protect electronics from lightning surges
Updated · 6 min read
Unplugging is the only complete protection. Short of that, layer a service-entrance surge protector with point-of-use units, and protect every path into the device: mains, network, coaxial and phone. A surge that cannot enter through the power lead will use the data cable instead.
Do surge protectors actually work?[1][2]
Good ones handle the induced surges from nearby strikes, which cause most equipment damage. None of them reliably survive a direct strike to the building. They are protection against the common case, not the extreme one.
The distinction that matters is between a direct hit and an induced transient. A strike hundreds of meters away pushes a spike into house wiring through electromagnetic coupling, and that is what a surge protector is designed to clamp.
A direct strike delivers energy orders of magnitude beyond what a point-of-use device can absorb. Anything relying on the mains supply during a direct hit is likely lost regardless of what is plugged in between.
Is a power strip a surge protector?[2]
Usually not. Most multi-outlet strips only split one socket into several, with no protective components inside. A genuine surge protector states a joule rating and a clamping voltage, and has a protection indicator light.
The indicator light is the part most people never check. Surge protectors sacrifice themselves progressively, and one that absorbed a large transient years ago may now be an ordinary power strip that still looks the part.
- Joule rating
- How much energy it can absorb before failing. Higher is better; under 400 is minimal
- Clamping voltage
- The level at which it starts diverting. Lower is better protection
- Protection indicator
- A light showing the components are still intact. Without one you cannot tell
- Data line protection
- Pass-through for coax, ethernet or phone, if those reach the device
- Replacement age
- Protective components degrade with each surge. Replace after a known event
Why do protected devices still get destroyed?[1]
Because the surge came in through an unprotected path. A computer on a good mains surge protector will still be destroyed by a spike arriving through its ethernet cable, and a TV protected on the power lead dies through the coaxial aerial feed.
Every conductor entering the building is an entry route: mains, cable TV, satellite feed, phone line, buried ethernet to an outbuilding, even a doorbell transformer. Protecting one and ignoring the others leaves the equipment exposed.
Outbuildings are a frequent weak point. A network cable run to a garage or shed picks up induced current over its length and delivers it straight into the switch it is plugged into at the house end.
What is the most effective protection?[2][3]
Physically disconnecting during a storm, which is the only method that is complete. For equipment that cannot be unplugged, a whole-house protector at the service entrance combined with point-of-use units gives layered protection.
The layered approach exists because the two tiers do different jobs. The service-entrance device takes the bulk of a large transient, and the point-of-use unit clamps what gets past it down to something the equipment tolerates.
| Approach | Protection | Practicality |
|---|---|---|
| Unplug everything | Complete | Only if you are home and have warning |
| Whole-house + point-of-use | Good against induced surges | Needs an electrician for the panel unit |
| Point-of-use only | Partial, mains path only | Easy, and what most people have |
| Plain power strip | None | Common and misleading |
| Nothing | None | Fine until it is not |
References
- How Powerful is Lightning?US National Weather Service, 2026
- Standard for the Installation of Lightning Protection SystemsNational Fire Protection Association, 2026
- Lightning SafetyUS National Weather Service, 2026
Related guides
- Why lightning destroys electronics without hitting the houseMost lightning damage to electronics comes from strikes that never hit the building. See how induced surges get onto wiring and what surge protection actually does.
- What to do if lightning strikes your houseCheck for fire first, including inside walls and the attic. The full sequence: safety, utilities, inspection and what to tell your insurer.
- How lightning rods and protection systems really workA lightning rod does not repel lightning or drain the cloud. It offers a preferred attachment point and a metal path to earth. See how the rolling sphere method places one.
- How powerful is lightning, in volts, amps and useful energy?About 300 million volts and 30,000 amps, against 120 volts from a wall socket. Why that power cannot be captured or stored, despite the arithmetic.