A guide to understanding power surges in your home

A guide to understanding power surges in your home
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This article, A guide to understanding power surges in your home originally appeared on Save On Energy by Terri Williams |

Power surges can be caused by a variety of factors – some internal and some external.  Some power surges are obvious, while others are less likely to be noticed, but can still cause problems. Protecting your appliances from power surges is a crucial part of maintaining your home’s overall electrical wellbeing.

So, what are power surges, and what causes them in the first place? How would you know if you’ve experienced one, and most importantly, what can you do to avoid them?

Here’s everything you need to know about power surges. 

What is a power surge?

Before we can determine how concerned you should be about power surges, it’s important to understand what it is. “A power surge, or transient, is a brief overvoltage spike or disturbance of a power waveform that can damage, degrade, or destroy electronic equipment in your home, and also in a commercial building, or industrial and manufacturing facility,” explained Brett Brenner, president of the Electrical Safety Foundation International (ESFI).  And he says they can reach amplitudes of tens of thousands of volts.

In your home, these power surges can damage many of your household appliances and shorten their lifespan. So, which appliances do power surges affect? “Heating and air conditioning systems, washers and dryers, water heaters, ranges and refrigerators, lighting, and entertainment systems” are at risk, according to Brenner.

What causes power surges?

There are several different causes of power surges. According to Brenner, internal sources of power surges caused by switching of electrical loads include:

• Contactor, relay, and breaker operations

• Switching of capacitor banks and loads

• Discharge of inductive devices (like motors and transfers)

• Fault or arc initiation

• Arcing faults

• Fault clearing or interruption

• Power system recovery (from an outage)

• DC battery storage systems

Brenner lists the following internal sources from magnetic and inductive coupling:

• Elevators

• HVAC (with variable frequency drives)

• Fluorescent light ballasts

• Copy machines

• Computers

In addition, Brenner identifies three external sources:

• Lighting

• Damage to power lines or transformers

• Grid and capacitor bank switching

What are the symptoms of a power surge?

Sometimes, it will be obvious when you’ve experienced a power surge. “Power surges happen in every home, every day, all day long,” said Benjamin Kolo, owner of Mr. Electric. “Power surges happen during storms, power outages, construction interruptions, and also accidents.”

Kolo says it’s very noticeable when there’s a storm and your lights start flickering and your microwave stops working. “These power surges are very destructive, and we notice them immediately,” he said.

However, there may be other power surges that happen all of the time – but we don’t notice – and these are the ones that could end up causing more damage than a thunderstorm.

“Every time an appliance turns on, the electrical system experiences a small drop, then a small surge to get back up to proper voltage until the system stabilizes,” Kolo explained.  “This may only take a second to stabilize, and a large surge is normally not experienced, but consider how many appliances turn off and on during a typical day: furnace, air conditioner, washing machine, pool pump, well pumps, dishwasher.”

In fact, Kolo said any appliance with a large current draw or motor will cause surges. “Most of the time, these small surges are not immediately catastrophic, but they occur day after day, month after month, year after year.” And each time, the sensitive electronics that control almost everything in your home take a small hit. “Over time, all those small hits can add up to significant damage,” Kolo said.

How to protect your home from power surges

So, what can you do to protect your appliances from power surges? Use surge protection. “A properly installed surge protector will act as an electronic sponge,” Kolo states.  “When there is a surge, the surge protector absorbs the variant voltage, then releases it back in the system when appropriate.”

Kolo explains there are three levels of protection:

Class 1: Whole house surge protection (installed where power enters the structure)

Class 2: Large appliance individual protection (installed near large appliances)

Class 3: Traditional surge strips

“All surge protection must be installed in conjunction with good grounding to work properly,” Kolo added. “Without proper grounding, the surge protection will not be very effective.”

Most homeowners are familiar with point-of-use surge protectors, and Brenner says that according to the 2020 National Electrical Code, surge protective devices are now required in homes.

“This kind of device only protects electronics plugged into the device, while installing whole-home surge protective devices will protect your entire electrical system and devices, ensure power quality, and keep your home safe,” Brenner said. He recommends hiring a qualified, licensed electrician to perform any electrical work required to install these devices.

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