Why do my Lights Flicker when the Air Conditioner Turns On?

It is common to see lights flicker briefly when a large appliance like an air conditioner turns on. This occurrence is typically tied to how much power these machines require to start up.

Inrush Current and Voltage Drops

When an air conditioner motor starts, it draws a surge of current that can be up to five times its normal operating load. This is known as inrush current. This sudden draw causes a momentary voltage drop in the circuit, resulting in a brief dimming of your lights. If the flickering only lasts for one to two seconds, it is considered normal and harmless.

When Flickering Signals a Problem

While a brief flicker is normal, certain patterns indicate serious electrical issues that require professional attention:

• Persistent Flickering: If the lights continue to flicker after the air conditioner has already started, there may be a loose service neutral connection. This is a dangerous condition that can cause fire risks or damage sensitive electronics.
• Whole-House Issues: If lights in multiple rooms dim simultaneously when the unit turns on, your electrical system may be struggling with the load.
• Overloaded Circuits: Frequent flickering combined with tripped breakers, warm switch plates, or buzzing sounds are symptoms of an overloaded electrical circuit. This means the circuit is pulling more current than its wiring is rated to handle.

Safety Warning Signs

You should immediately turn off your appliance and contact a licensed electrician if you notice any of the following “red flags”:

• A burning or acrid smell near the electrical panel or outlets.
• Discolored or warm switch plates.
• Persistent flickering that does not stop after the initial startup of the appliance.

• Flickering Lights in House Troubleshooting: Complete Homeowner’s Guide