Is it OK to run your air conditioner during a thunderstorm?

The hot, humid summer conditions that make you want to crank the air conditioner also create the ideal conditions for thunderstorms. Operating your air conditioner during a thunderstorm can lead to some damage to your unit, but the chances are slim.

If you want to be super-cautious, you can turn your air conditioner off at the breaker box during a thunderstorm. Luckily, humidity and temperature drop when storms roll in, so you’ll get some relief even though your air conditioner is not in use.

Why consider turning off your air conditioner during a thunderstorm?

• Lightning strikes. While lightning strikes to the home are rare, they are a possibility during a storm. The electrical service drop, where your utility lines connect to the house on the roof, is a very vulnerable point for lightning strikes. If lightning strikes at this point, it can cause a significant power surge through your home’s electrical system. As much as 5 billion joules of energy can be sent through your home’s wiring before the breakers are triggered to trip. In a fraction of a second, the surge can cause serious damage to your air conditioner if it is operating.
• Air conditioner damage. The damage caused by a lightning strike can render your air conditioner unusable. It can melt the plug to your unit. The air conditioner’s control panel is full of sensitive electrical circuitry which can be damaged, requiring an extensive repair or even replacement of the entire unit. The system’s controls can be corrupted to the entire heating and cooling system if a lightning strike occurs when the system is operating.

Can lightning strike a window air conditioner?

Yes, lightning can strike a window air conditioner, particularly if you live in an apartment building or high-rise and are further from the ground. However, this is highly unlikely. Lightning strikes are statistically very rare and it is generally safe to leave your window AC unit plugged in. Air conditioners are electrically insulated to remain safe in the event of a surge. The refrigerant inside the unit is nonflammable, so you aren’t in danger of an explosion. 

A power surge could melt the plug and power port on your unit, and damage the circuitry in your control panel. That can be a costly repair, and you may end up needing an entirely new window unit which can cost up to $600 to purchase and install. 

If you want to take extra precautions, you can unplug your window unit during the storm and plug it back in once it passes. 

How do I protect my air conditioner in a thunderstorm?

If you happen to live in an area with a high occurrence of lightning strikes, you can protect your air conditioner by installing a protection system. Using lightning rods, conductors, and ground rods, you’ll create an alternate path for lightning to reach the ground, avoiding your home’s electrical system.

If you live in a hurricane-prone area, check out our tips for preparing your AC for a hurricane.

Can I use my AC in a rainstorm?

It’s perfectly safe to run your AC during a rainstorm. Rain will not interfere with the outdoor unit’s ability to function correctly. In fact, using your AC on warm, rainy days can keep your home more comfortable — your indoor evaporator coils extract moisture and lower humidity levels, which improves comfort levels indoors.

If rainstorms result in flooding and you have standing water around your unit, you should stop using the system, and turn off power at your home’s electrical panel to prevent damage. Have your unit inspected by an HVAC professional before using it after flooding.