Understanding Why Lights Flicker When Your AC Unit Turns On

Do your lights flicker just after you’ve turned on your AC unit? If so, there’s no need to panic, as it’s common for many homeowners.

If your lights flicker for a few seconds after you turn on the AC unit, there’s usually nothing to worry about since it’s caused by the AC unit using up a lot of power. However, flickering may also be caused by broken or exposed wires, a damaged capacitor, or a faulty start-up surge. 

If the flickering occurs for a longer period and the lights dim significantly, there is a larger issue. Ideally, you should find the cause of the problem and have a qualified electrician fix it before the issue worsens. 

Consequences of Not Fixing the Problem 

Even though the flickering lights are not a major problem, it is something that needs to be taken seriously. The problem could be caused by faulty wiring, which, if left unattended, could even result in an electrical fire. Even though it is unlikely to happen, you’re better off getting it checked out and fixed.

Insufficient or outdated wiring can also be the culprit in this situation. This could be a major issue because you won’t be able to use many appliances while your AC is turned on. The wiring may not even be compatible with your air conditioning unit. 

Reasons Why Your Lights are Flickering when Air Conditioning is Turned On

There are a few reasons why your lights flicker after you turn on the AC, and much of it has to do with wiring, among other issues. Some of these are not a big threat or issue, and you may find that you can resolve them independently. 

Others, however, will require it to be dealt with by a professional and can turn out to be more costly. Let’s take a look at the main causes behind your flickering lights issue:

You Have Damaged or Loosed Wires 

Damaged and loose wires or parts are the leading cause behind the flickering lights issue in most households and possibly others, such as humming. The main indication that this is the reason behind your flickering lights problem is if the light bulb flickers on and off rapidly. 

The loose wiring means less power reaching the lightbulb, and turning on the AC highlights that even more.  The good news is that it isn’t that costly or difficult to fix, even if you hire a professional to come in.

Weak or Broken Capacitor 

A capacitor is a part of the AC that works like a car battery and helps give the boost required to start it. A bad or broken one can cause various problems, such as ac buzzing or whistling.

If it gets damaged or is broken, the AC will need much more power to start up. It will then begin pulling electricity away from other appliances in your home to meet the power requirement it needs to start up and function. 

If this is the problem, you will notice a reduction in power by up to 40 percent, as well as your lights dimming significantly. Unfortunately, this is a much more costly problem to fix, as you may need to get a new capacitor.

Overloaded circuits 

There are a few different circuits in a house that are all connected to an electric board or electric panel.

If a specific circuit begins pulling too much electricity at once, the circuit will overload and trip. If this happens, ensure that no other appliances are connected to the same circuit as your AC.

Exposed wires

The most dangerous possibility that could be causing the issue of flickering lights is exposed wires at the back of your AC. You must take extreme caution if this is the case, as the bare wires could result in electrocution and equipment damage. 

It is advised not to touch or get close to the wires without shutting off the electric connection first. Another issue with exposed wires is that it may result in an electrical fire if it gets too hot. The good news is that it is easy to identify and fix.

Distribution Panel is Maxed Out 

A distribution panel that is maxed out means that you’ve reached the limit of voltage that can run through the distribution panel for your household. This often happens when you have too many major appliances running simultaneously.

When your lights begin flickering, it’s a sign that the electricity consumption is too high and that there’s a possibility of a power failure. If this happens, switch off those major appliances immediately and be careful not to overload the panel.

Faulty Start-up Surge 

If your lights flicker for only a few seconds as you switch on the AC, it’s probably a start-up surge. A start-up surge occurs when more power is directed to the AC unit because it requires a lot of power to start up. This causes less electricity to be available throughout the rest of the circuit for a fraction of a second. 

Start-up surges are not anything to worry about as they do not pose any major threat. However, if the flickering irritates you, you can call a professional electrician and get it sorted out.

How Do I Know My Problem is Serious? 

When turning on your AC, notice how long the flickering lasts and how intense it is. If the light flickers for a fraction of a second or even a few seconds, it most likely isn’t a serious problem and just a faulty start-up surge.

However, if the flickering is prolonged for over 5 seconds and the lights dim significantly, you will likely have a serious problem and need to get it checked out. These are some of the questions you need to ask to get a better understanding of whether you’re dealing with a serious issue or not:

  • Do lights flicker every time you turn them on? 
  • Is it happening in just one room or the whole house?
  • Does it flicker for a brief moment, or does it stay flickering?

If your lights flicker every time you turn them on, it’s most likely caused by faulty wiring. This isn’t a very serious issue, but you should get it fixed as soon as possible. 

If the flickering is happening around the whole house, then it is a serious issue. In this case, it is most likely to be caused when the distribution panel is maxed out and you’re using too much electricity simultaneously. This is dangerous because it could cause long-term damage to many of your appliances.

Another thing to look out for is if you hear clicking sounds coming from your AC after you turn it on. If so, this indicates that the capacitor is broken or damaged and needs to be replaced. 

How to Fix the Flickering Problem 

Having flickering lights at home is annoying and unbearable. So, the best way to fix the flickering problem is to first identify the issue to the best of your ability. If you follow the steps mentioned above, you should be able to get a rough idea of what’s causing the issue. 

Most of the major issues are caused by an aging or broken capacitor in the AC unit. Unfortunately, you’ll need to replace that, which will cost anywhere between $180- $450. Always get the capacitor replaced by a professional unless you’re an electrician.

If you are struggling to figure out what the cause of the problem is, just get a professional to come in and take a look for you. They’ll find out the issue in no time and fix it for you on the spot. However, you do not need an electrician to come and change a light bulb. So, if only one light flickers, change it first and see if it helps.

On the other hand, if you notice that it’s a case of loose or exposed wires, then that’s a serious problem. In this case, you will need an electrician to sort it out for you as soon as possible. 

Damaged wires can result in sparks and even electrical fires, so make sure you seek repairs immediately. Some tasks are best left to the professionals, as DIY solutions can become dangerous in these scenarios. 


While it may seem strange that your lights flicker momentarily when you turn your AC unit on, it’s usually nothing major. However, as with all electrical anomalies, always have the issue checked, especially if it happens repeatedly. 

In some cases, electrical faults, such as capacitor problems or damaged wires, may be behind the issue. This can lead to serious problems down the line. So, if you notice flickering lights when you turn the AC unit on, have it checked by an electrician right away.

In the worst-case scenario, you’ll have to replace the AC unit’s capacitor. However, in most cases, you can resolve the problem with minor electrical fixes.