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Air Conditioning

How To Protect Your Air Conditioner From Lightning Strikes

 May 3, 2020

By  Robert Bradford

Lightning strikes are common during a thunderstorm and can cause severe damage to your air conditioner and other electrically powered systems inside your home. Since lightning DOES strike the same place twice, it is best to rethink how your family and your air conditioner can be protected from this natural but dangerous phenomenon.

While it is unusual for lightning strikes to hit an air conditioner, the more critical threat is the power surge that frequently follows it. A power surge is a sudden increase in energy in your home’s electrical current. Another common problem is brownouts (low voltage) that can occur during and after a thunderstorm.

A power surge brought about by lightning striking a power line near your house can boost electrical force by millions of volts. The damage to appliances such as your air conditioner can be instantaneous. It can fry the circuits or melt the plastic and metal parts of the machine.

Even mild power surges can gradually damage electronic devices in your home when they occur briefly but frequently.

There are two ways to protect your air conditioner and other electronically powered systems in your home from lightning strikes, power surges, and brownouts:

  • Turn off your air conditioner during a thunderstorm.
  • Install air conditioner surge and low voltage protector.

Are lightning strikes a serious problem? The National Severe Storms Laboratory reported that lightning strikes the ground an estimated 25 million times each year in the United States. As much as we want to protect ourselves and our family from these frightening occurrences, we also want to protect our belongings that make our home safe and comfortable.

First, we would like to know more about lightning and how this tremendous work of nature could impact homeowners.

Why Do Lightning Strikes Occur?

Lightning is defined by the National Geographic as “an electrical discharge caused by imbalances between storm clouds and the ground, or within the clouds themselves.”

Clouds have positive and negative charges within themselves that pull toward each other like a magnet. In normal conditions, these two charges balance each other out. However, when there is a storm, the turbulence in the wind moves the elements of rain, ice, or snow to clash with each other inside the storm clouds.

This commotion inside the cloud separates particles with different charges from each other: positively charged particles are pulled in the upper portion of the cloud and the negatively charged ones are pushed to the lower reaches of the cloud.

Most lightning happens inside the clouds so how and why does it strike the ground?

The Earth and almost everything in the ground become positively charged. Since the negatively charged particles are attracted to positive ones, they race their way down in a step-like fashion. It is called by scientists as a “stepped leader”.  Its rapid movement is measured at about 300,000 kilometers per hour (kph).

The stepped leader from above is eagerly met by what experts call an “upward leader” or a “streamer”, positive charges coming from the ground and through tall objects such as towers, buildings, and trees. When they finally meet, a very bright flash of electrical current flows that shoots upward into the clouds at 300,000,000 kph. This astonishing transfer of electricity is what we typically refer to as a lightning strike.

Damages Caused by Lightning Strikes

The heat from a single lightning strike is very intense. The National Geographic explains that a flash is capable of heating the air temperature around it to “five times hotter than the sun’s surface.” Due to the extreme heat, the air quickly swells and trembles which results in thunders.

Although an air conditioner is rarely directly hit by a scorching lightning strike, we should not discount the possibility of it ever happening. 

What you should be more worried about is the power surge produced by a lightning strike to nearby power lines. If your air conditioner is running when it happens, a power surge can send an enormous amount of electrical current through it and ruin it instantly.

Common Repair Costs After Lightning Strikes

The costs to repair your air conditioner after a lightning strike can be significant. Some repairs needed will become apparent immediately. On the other hand, the effects of power surges on your air conditioner unit could show up much later. After some time your air conditioner could even suddenly quit due to the damage it has sustained. Here are some common problems and their costs:

  • Compressor Damage

    The compressor is a crucial component of your air conditioner. It is responsible for compressing the refrigerant that removes the heat from the warm air inside your living space. Replacing it can range from $800 to $2,800.
  • Capacitor Damage

    The capacitor’s role is to conduct energy to the engine that powers your air conditioner. It is the most susceptible part of the air conditioner when power surges occur. If damaged, it can cost you somewhere between $100 to $400.
  • Fuse or Breaker Damage

    The job of an air conditioner fuse is to prevent electrical overload. If lightning strikes a power source where your A/C is connected, the fuses could be blown because of the huge amount of electricity it suddenly has to control. It will cost you around $15 to $300 to replace A/C fuses. Although not as pricey as other components, it is still an inconvenience to replace.
  • Wire Damage

    Like a blown fuse, wiring in an air conditioner can be overwhelmed by an abrupt upsurge of power due to a lightning strike. This may lead to the burning of electrical wires. The cost of replacing the wires depends on the extent of the damage. Depending on the damage it may cost somewhere between $100 to $400.

Ways to Protect Your Air Conditioner from Lightning Strikes

Prevention has been and will always be better than cure. Although lightning strikes are terrifying and can cause long-term damages, you can save your air conditioner and other electrical devices with these simple steps:

1. Turn off your air conditioner during a thunderstorm.

It could be tempting to crank up your air conditioner before a thunderstorm begins because of the muggy and sticky feeling an impending storm brings. However, turning the air conditioner off is the easiest way to reduce the potential for damages from lightning strikes.

While this solution is the easiest and free it’s also the most likely not to work. You can’t always predict when a power surge or brownout will occur. It’s also why I don’t recommend relying on this solution.

2. Install air conditioner surge and low voltage protector.

This is called point-of-use protection. From the name itself, surge protector shields your air conditioner from voltage spikes. The ideal choice is one that protects from both high and low voltage to the air conditioner. The best ones I’ve found and have used for years is the Intermatic CD1-024R Compressor Defender and the Intermatic AG3000 for the air handler or furnace.

Protects Central Air Conditioner and Heat Pump Compressors and their Circuit Boards

120/240 VAC Universal HVAC Surge Protective Device

They are easy to install for an HVAC technician, electrician or someone who has previous experience working with electric panels. If you don’t have any of those qualifications I highly recommend hiring one of those professionals to install these devices. 

This surge protector can sense if there are surges, spikes or brownouts in the voltage it receives. The surge protector will divert the extra energy to the grounding system and away from the air conditioner.

You can identify a quality surge protector if the description provides a joules energy rating. The higher the joules rating is, the better performing your surge protector will be. Additionally, a reliable surge protector should come with a warranty. A Intermatic devices, for example, are protected by a $7,500 connected equipment guarantee. The peace of mind it provides is priceless.

Robert Bradford


I'm Robert Bradford. I've been in the heating and air conditioning industry for 30 years. Ov​​​​​er 40 if you count the years I helped my father as a kid. On this site, I share everything I've learned about finding the best HVAC contractors and equipment for your home. I'm happy to say that over the last few years, The Comfort Academy has grown into a trusted site with thousands of informed site visitors each year.

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