What Is an Electrical Power Surge?

Jenna Jonaitis
Written by Jenna Jonaitis
Updated May 19, 2023
shot of woman in gray shirt plugging in power cord of coffee pot to electrical outlet
Photo: Maskot / Maskot / Getty Images

An electrical power surge is a sudden and short increase in voltage in an electrical circuit, which can damage sensitive electronics

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Most of us feel pretty safe inside the house when a lightning storm is raging outside. But we're surrounded by a bunch of things that are in danger: our electronics.

One lightning strike in the right place and bam, a power surge hits your television. That means even when the power comes back on, the TV may not. Of course, lightning isn't the only cause of power surges—in fact, it’s not even the most common. Read on to learn about what power surges are, what causes them, and how to protect your electronics.

What Is a Power Surge?

Power surges are higher-than-normal surges of electricity. Your electronics are fragile and can only handle so much electrical current. If a surge of electricity overwhelms the electronic device's voltage limits, they can be "fried." And it may not happen all at once: Small power surges over time can gradually degrade your electronics.

More technically speaking, a surge is a transient wave of current or "overvoltage" that lasts a short period of time. These transients can sometimes contain tens of thousands of volts and last just microseconds.

What Causes a Power Surge?

While most people think of lightning strikes when they think of power surges, an estimated 60 to 80% of power surges come from inside the house. Yes, turning large appliances on and off or even flicking the thermostat switch are the most common power surge causes. 

Power Outage

Power outages happen when there’s a large-scale power grid failure. The outage itself might not cause a power surge, but the reconnection to power can. A sudden jump in the current often occurs when power restores after an outage. The surge can cause damage to appliances and devices plugged in that don’t have a surge protector.

Electrical Overload

An overload can occur when too much power draws from a single circuit, like when you use too many devices at once or when there's an overuse of extension cords. The massive current causes a voltage spike, and the circuit becomes overwhelmed. Space heaters, hairdryers, power tools, and large appliances are common culprits for triggering an electrical overload. 

Faulty Wiring

Damaged, faulty, or exposed wiring in your home can also cause power surges. These wiring issues are often hidden in your walls and difficult to identify on your own. Signs of faulty wiring include outlets with burn marks, a burning smell, a buzzing sound, or a circuit breaker that trips frequently. If you notice any of these signs, unplug your electronic devices and appliances and contact a local electrician.


If lightning strikes your power line or electrical system, it can cause an excessive current, leading to a power surge. Power surges from lightning are rare but are significant when they occur. If you expect a severe storm in your area, unplug any devices that don’t have surge protectors.

Other causes of power surges include:

  • Appliances (such as refrigerators, dishwashers, air conditioners, microwaves, and washing machines)

  • Downed power lines

  • Bad equipment from the utility company

  • Tripped circuit breakers

  • Short circuits

  • Power company malfunctions

Signs a Power Surge is Coming

A power surge may be expected if you notice these signs:

  • Buzzing noises coming from lights or outlets

  • Flickering or dimming lights

  • Frayed or damaged wiring

  • Burns or discoloration on outlets or near wires

  • Smoke coming out of outlets

  • Warm or vibrating outlets

  • Burning smell coming from outlets 

Signs a Power Surge Has Happened in Your Home

A power surge may have occurred if you notice the following signs: 

  • Flashing lights on digital clocks

  • Appliances and devices turning off or not working

  • Pungent smell surrounding a device or appliance

  • Surge protectors and power strips need to be reset

  • Power quickly going on and off in your home

  • A sudden return to power after a long power outage

What to Do After a Power Surge 

If you’ve experienced a power surge, take these steps to ensure your home and devices are safe and ready for use. 

1. Reset and Repower Your Devices

Unplug any devices that were plugged in during the surge. Then reset the circuit breaker and plug your devices back in. 

2. Assess Your Home and Appliances

Ensure your appliances, electronics, and electrical outlets have not been damaged. Take note of any outlets that aren’t working, have burn marks, or have pungent odors. If you notice any damage to your appliances, reset the device and circuit breaker to see if that’s the issue. Contact an electrician if you notice burnt or odorous outlets. 

3. Check Your HVAC System

Make sure your HVAC systems are working properly. If you notice any issues, reach out to a local HVAC technician.

4. Contact a Licensed Electrician

If you notice ongoing issues after a power surge, such as breakers that continue to trip or lights that keep flickering or going out, contact a licensed electrician in your area. You may have damaged wiring, increasing the risk of fire and personal injury.

Are Power Surges Dangerous?

While power surges are primarily a danger to sensitive electronics, they can be dangerous to people. A strong surge can cause an appliance to overheat or even catch fire.

The more severe the surge, the more likely it is to cause overheating and a fire. Switching appliances on and off doesn't cause as severe of a spike as, say, a lightning strike, but all surges carry a small risk of fire. While the risk is low, a surge protector can help protect you from potential disasters.

closeup of charger in electrical outlet with woman in bed on her phone blurry in the background
Photo: dowell / Moment / Getty Images

What Will a Power Surge Do to My Electronics?

Household electrical systems tend to run an alternating current rated at 120 volts and 60 hertz, but maxes out at 169 volts (with a minimum of 0).

A power surge causes the voltage to exceed 169 volts, which is harmful because it causes the electrical current to go above the normal operating voltage. This, in turn, creates an arc of electrical current that damages circuit boards and the various components that help run your appliances and devices. Smaller electrical surges cause damage more slowly and may shorten the lifespan of the device or appliance. This is why many homeowners deem surge protectors a good investment.

What Is a Surge Protector and How Does It Work?

A surge protector doesn't block the surge; it simply redirects a sudden increase in voltage into the ground.

Most surge protectors come in the form of a power strip that you can plug multiple devices into, protecting all of them at once. When the power spikes past a designated level of voltage, the surge protector diverts the extra current into grounding wires, giving the electricity a pathway away from the devices.

Are All Power Strips Surge Protectors? 

While power strips and surge protectors look similar, only the surge protector will keep electronics from getting fried by excess electricity. A standard power strip is simply a device that allows you to have extra outlets. These strips are basically just extension cords without the additional protection.

Check the packaging to ensure it’s a surge protector before buying it—there should be a Joules rating on it. If it says 2,000 Joules, that means it can take 2,000 Joules worth of power surges before it’s no longer effective.

How to Protect Your Home and Electronics From Power Surges

A surge protector isn’t a fool-proof way to prevent the damage and possible expenses of a power surge. A particularly strong surge could still overwhelm a surge protector, or only some of your devices may be connected to the protector. One bad power surge could leave you out thousands of dollars.

A professional electrician can inspect your home to ensure no flaws could lead to a surge. They might recommend updating your home's electrical system or installing a whole-home surge protector. You'll need a professional for most electrical upgrades.

D.P. Taylor contributed to this piece. 

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