Why Do My Lights Dim When The AC Turns On?
If you’ve ever noticed that your lights dim when the AC turns on, you’re not alone. Many homeowners in Bryan and College Station experience this issue, especially during the hot Texas summers when air conditioners are running full force. While a slight dimming may seem harmless, it can also signal underlying electrical problems that should not be ignored.
At Gilmore Electric Express, we often receive calls from customers concerned about flickering or dimming lights when large appliances cycle on. In this post, we’ll explain the most common reasons this happens, when it’s considered normal, and when you should call an electrician to inspect your system.
Why Does the AC Cause Lights to Dim?
Your air conditioner requires a significant amount of power to start. When it kicks on, it draws a large surge of electricity, called inrush current. This sudden demand can cause voltage fluctuations throughout your electrical system, leading to a brief dimming of lights. The U.S. Department of Energy notes that central air conditioners use more electricity than almost any other appliance in your home, which explains why the effect can be noticeable.
In most cases, a slight, momentary dimming is common and not dangerous. However, if the lights dim dramatically, flicker frequently, or stay dim longer than a second or two, it may be a sign of a bigger issue.
Common Causes of Lights Dimming When The AC Turns On
- Normal Voltage Drop
As mentioned, the inrush current from your AC can cause a small, temporary drop in voltage. If the dimming is mild and short-lived, this may be normal. - Undersized Electrical Panel
If your home has an outdated or undersized electrical panel, it may not handle the demand of modern appliances. The National Electrical Code recommends that panels be properly sized for your home’s load capacity. - Loose or Aging Wiring
Loose connections, corroded wires, or degraded components can magnify the effect of voltage drops, making lights dim more severely when the AC cycles on. - Shared Circuits
If your lighting and HVAC system are on the same circuit or breaker, the demand can cause visible dimming. Ideally, large appliances like air conditioners should be on dedicated circuits. - Faulty Capacitor or AC Components
Sometimes the issue isn’t with your home’s wiring but with the air conditioner itself. A failing capacitor or compressor may draw more current than normal, creating noticeable dips in power. - Utility Supply Issues
In some cases, the problem lies outside your home. If your neighborhood’s grid is overloaded, or if there’s an issue with the transformer supplying your street, you may experience dimming.
When Is It a Problem?
Slight dimming for less than a second is usually normal. But you should schedule service if:
- Lights dim by more than 10% of brightness
- Dimming lasts longer than a second or two
- Lights flicker or pulse repeatedly
- Appliances trip breakers when turning on
- You smell burning or notice warm outlets
According to the U.S. Fire Administration, in 2021, an estimated 24,200 residential building electrical fires were reported to United States fire departments. Faulty wiring and overloaded circuits are major causes of residential electrical fires —which is why electrical issues should never be ignored.
What Can Be Done to Fix It?
Here are some potential solutions:
- Electrical Panel Upgrade: Replacing an old or undersized breaker panel can eliminate many dimming issues.
- Dedicated Circuits: Installing separate circuits for high-power appliances reduces the load on your lighting circuits.
- Wiring Repairs: Replacing or tightening loose, damaged, or outdated wiring improves electrical flow.
- AC Maintenance: Having an HVAC technician inspect your air conditioner may uncover problems with the capacitor, compressor, or other components that are overloading the system.
- Whole-House Surge Protection: Protecting your home from power surges keeps your electrical system stable and safe.
If you’re experiencing persistent issues with lights dimming when the AC turns on, it’s a good idea to have a licensed electrician evaluate your system. A professional can measure voltage fluctuations and determine whether the problem is with your home’s wiring, your electrical panel, or the AC unit itself.
Why Call Gilmore Electric Express?
As a family-owned company serving Bryan, College Station, and the entire Brazos Valley for three generations, Gilmore Electric Express specializes in diagnosing and repairing electrical problems quickly and safely. We offer full electrical repair and installation services for both residential and commercial clients. Our licensed team provides upfront pricing, on-time service, and 100% satisfaction guaranteed.
When it comes to something as important as your home’s electrical safety, don’t take chances. Whether you need a simple repair or a full electrical panel upgrade, we’re here to help.
Schedule Your Service Today
If you’ve noticed your lights dim when the AC turns on, it may be time to take a closer look at your electrical system. Schedule an appointment with Gilmore Electric Express today to get expert help from trusted electricians in Bryan and College Station. Contact us today to book your service and keep your home’s power safe and reliable.