Why Are My Lights Flickering When My AC Turns On?

image of a kitchen lights depicting lights flickering when ac  unit turns on

If you have observed flickering or dimming lights when you turn on your cooling unit, you are not alone. This occurrence is frequently encountered and can stem from various factors. This guide will delve into the most prevalent causes of flickering lights when your AC is turned on, including electrical issues, wiring problems, and outdated equipment. We will also offer practical tips and guidance on addressing and resolving the problem, along with guidance on when it is advisable to seek assistance from a professional. 

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Is It Normal for Lights to Flicker When the Air Conditioner Turns On?

It is not uncommon for home lights to flicker when the air conditioning system is activated. This occurs because the AC unit requires substantial electricity to start up. The sudden surge in power consumption can cause a momentary voltage drop, resulting in lights flickering.

When the AC compressor initiates, it demands a significant power draw to cool the air. This sudden electrical load can lead to a temporary voltage decrease in the home’s electrical system, affecting other appliances on the same circuit, including lights. As the AC stabilizes, the voltage should return to normal, and the lights should stop flickering.

However, if the flickering persists or becomes severe, it may indicate a more significant issue, such as an overloaded circuit or faulty wiring. In such cases, consult a qualified electrician who can assess the situation and perform any necessary repairs or upgrades to the electrical system.

The following expectations apply unless you have a geothermal unit:

  • Brief flickering or dimming of lights
  • Dimming of lights ranging from 3-5% or potentially more

Standard outdoor air conditioning units draw a higher electrical load than geothermal units, as geothermal units derive energy from the earth’s natural heat. The AC control unit is typically located alongside the furnace in geothermal systems. If your geothermal unit is placing a significant strain on your electrical system, it requires the expertise of a specialist.

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Related Article: Air Conditioner Makes Loud Noise When Starting

Signs of a Major Air Conditioner Issue

HVAC technician working on controls of air conditioner

Experiencing flickering lights when the AC turns on could mean a more significant problem with the electrical system. Here are some potential causes of persistent or severe flickering:

  1. Overloaded circuit: If the circuit carrying both the AC and lights is overloaded, it can lead to flickering lights. This poses a safety risk and can cause damage to the electrical system over time.
  2. Faulty wiring: Faulty or outdated wiring can result in voltage drops and other electrical issues. If the flickering persists, it may indicate the need for wiring repairs or replacements.
  3. Low voltage: Insufficient voltage supplied to your home can cause home lights to flicker when the AC starts. This may be due to power grid problems or issues with the transformer delivering power to your residence.
  4. Damaged or weakened AC capacitor: Similar to a weak or faulty car battery, a damaged or weakened AC capacitor can cause a significant decrease in electrical power, leading to noticeable light dimming. If this problem arises, it is recommended to seek professional assistance to assess and address the AC capacitor.
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Ways to Prevent Lights from Flickering When the Air Conditioner is Turned On

Experiencing flickering lights when you turn on your air conditioner can be frustrating, but you can take steps to address the issue. Here are some easy and easy tips to help you prevent lights from flickering:

  1. Ensure proper electrical connections: Make sure all electrical connections related to your air conditioner and lighting fixtures are secure. Loose connections can cause voltage drops and flickering. If you are unsure about electrical work, consult a professional electrician.
  2. Balance electrical loads: Avoid overloading circuits by distributing electrical loads evenly. Consider having dedicated circuits for high-power appliances like air conditioners to prevent excessive strain on the electrical system.
  3. Upgrade wiring if needed: Outdated or faulty wiring can contribute to flickering lights. If you suspect wiring issues, have a qualified electrician inspect and upgrade the wiring if necessary.
  4. Install voltage stabilizers: Voltage stabilizers, also known as surge protectors or voltage regulators, can help regulate and stabilize the voltage supply to your home. These devices can minimize fluctuations and prevent flickering lights.
  5. Seek professional assistance: If flickering lights persist or worsen despite your efforts, call an experienced HVAC technician or electrician. They have the expertise and training to diagnose and resolve any underlying electrical or air conditioning system issues.

Related Article: Portable Dehumidifier Vs. Air Conditioner: Which Is Best?

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Don’t DIY Air Conditioning Repair – Call An HVAC Contractor

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For safety reasons, avoid DIY attempts when dealing with electrical issues related to air conditioning or lighting systems. Working with electricity can be extremely hazardous and pose serious risks, including severe injury or even death if mishandled. Air conditioning and lighting systems operate at high voltages, making them potentially dangerous for individuals without proper training in electrical work.

Apart from the physical dangers, attempting to fix electrical issues without the appropriate expertise can further damage the system and potentially lead to expensive repairs. Electrical systems are intricate. Even seemingly simple problems may have underlying causes that need the expertise of a trained professional to identify and address.

Always hire a licensed and qualified electrician to handle any electrical issues to ensure safety and effectiveness. These professionals possess the necessary knowledge, training, and equipment to perform the work correctly, keeping your home or business secure and functional. Prioritizing professional assistance is essential for the well-being of yourself and others.

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Related Article: Why Is HVAC Airflow So Important For My Home?


Being attentive to lights flickering when the AC turns on is crucial for ensuring home safety, comfort, and peace of mind. These flickering lights can indicate underlying electrical issues that require immediate attention from qualified technicians or electricians. Neglecting these signs may lead to more significant electrical problems down the line. Adopt a proactive and vigilant approach to identifying and addressing these issues promptly. Taking timely action ensures that your home remains safe, comfortable, and free from electrical complications. 

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