How to Protect Your Appliances from Lightning and Power Surges: Which Protection for Each One

What a power surge is and where it comes from

The voltage at your outlets should always be the same, but sometimes it jumps. The U.S. National Institute of Standards and Technology (NIST) explains it in its home guide: lightning, a short circuit or a pole knocked down can make the voltage jump to hundreds or thousands of volts for a few millionths of a second. That’s enough to destroy a device or upset its settings, and in rare cases to start a fire. That jump is called a surge.

According to NIST, surges come from two sources: lightning, which can affect appliances even when it strikes far away, and switching, when large appliances are turned on or off at home or the power company makes changes on the grid. And they don’t only come in through the power line: also through the phone line, the antenna or the cable TV.

There are other problems besides surges. Voltage sags rarely damage appliances, though they can make a computer restart. Swells, longer increases in voltage, can damage them if they’re very large or last long. And then there are outages. Each problem has its own protection.

The protections and what each one does

The table sums up what NIST and Mexico’s Federal Consumer Protection Agency (Profeco) say. Profeco puts it this way: if your concern is a rise or drop in voltage damaging your appliances, the choice is a regulator; if you want them to keep running when the power goes out, a UPS. In its December 2025 quality study it tested 11 regulators and 12 UPS units, and found products of similar quality at very different prices, and some with incomplete warranties.

Which protection suits each appliance

NIST sorts household appliances into groups, from least to most vulnerable:

• Motor-driven and heating appliances with mechanical controls (dials, on-off switches): older washers, heaters, toasters, incandescent bulbs. They generally withstand the normal surges in a home. If they have electronic controls (display, keypad, programs), they’re more vulnerable.
• Electronic devices connected only to the power: a TV with an indoor antenna, a computer with no network cable, a radio. A simple plug-in surge protector is usually enough, and many already have protection built in.
• Devices connected to the power and to another line: a TV with cable or satellite; a computer or router connected to the phone line or cable. These are the most vulnerable, because the surge can come in on either line. For them NIST recommends a combined protector, with outlets and inputs for the antenna or phone cable in the same box.
• An ordinary lamp: according to NIST, a protector costs more than replacing the lamp if it’s damaged, so it isn’t worth it.

For the computer, as well as a surge protector, a UPS keeps you from losing work during a sag or outage. For the fridge, many countries sell voltage protectors that disconnect it if the voltage rises or drops and wait before reconnecting. We haven’t found any official body that has evaluated them; if you buy one, make sure it carries a safety certification.

When buying any protector, NIST advises checking it has been tested by a safety laboratory (their marks are on the box), reading what its lights mean and keeping the explanation, and looking at the joules: the more, the more surge energy it can absorb. Protectors work by diverting the surge to ground, and NIST warns that some don’t work well in outlets without a ground: if your home doesn’t have grounded outlets, ask an electrician.

During a thunderstorm

The U.S. National Weather Service explains that lightning can enter a home through the power, phone and antenna wiring, and through the pipes. Its advice:

• Unplug devices before the storm arrives, not during: unplugging them in the middle of a storm is dangerous for you.
• During the storm, don’t touch electrical equipment or cords, such as the computer or TV. The remote control is safe to use.
• Don’t use corded phones; mobile or cordless phones are fine.
• Avoid water: no showers, washing dishes or washing your hands.
• And an important warning: an ordinary surge protector won’t protect devices from lightning.

A detail from NIST: if you unplug a device from the power while it’s still connected to the antenna or phone cable, it loses the grounding the plug provides, which can be dangerous if a surge comes in on that cable. If you disconnect it, disconnect that cable too.

If you have no protection at all

• When a storm is coming, unplug in good time the devices you care about most, including the antenna or cable.
• When the power goes out, switch off or unplug your appliances: Ready.gov, the U.S. government’s emergency website, warns that power may come back with surges that can damage them.
• Unplug what you’re not using: according to NIST, a device that’s only plugged in now and then is at much lower risk than one connected all day.
• Start with the most vulnerable and expensive: the TV with antenna or cable, the computer and the router.

When to call an electrician

A surge protector at the electrical panel, a lightning rod, the home’s grounding and any change to the wiring are jobs for a qualified electrician or professionals. If surges or outages are frequent where you live, also ask your power company: according to NIST, some offer to install a surge protector at the meter.

If outages are your problem, also see what battery or power station you need and how long fridge food lasts.