Lights often flicker or dim briefly when an appliance turns on because the appliance draws a burst of extra current as it starts, which can cause a short drop in voltage. A quick, slight flicker can be normal, but strong or frequent flickering may point to an overloaded circuit, a loose connection or a service problem.
The details of the flicker help show whether it needs attention.
Why Appliances Cause a Brief Dip
Appliances with motors or compressors, such as air conditioners, refrigerators, washers, vacuum cleaners and sump pumps, draw much more current for a moment when they start. Space heaters and hair dryers can also pull a heavy load.
That sudden demand can lower the voltage slightly on the circuit, and sometimes across the home. Lights on the same circuit may dim or flicker for a split second, then return to normal.
Some LED bulbs are more sensitive to small voltage changes than older bulbs, so the flicker may be easier to notice.
When the Flicker Is Worth a Closer Look
A brief dip when a large appliance starts is not always a problem. It becomes more concerning when the lights dim a lot, flicker for a long time or flicker even with small appliances.
If the flickering affects lights throughout the home rather than one circuit, the problem may involve the main panel or the service connection. Loose connections at these points can cause voltage to drop more than it should.
Flickering that gets worse over time, or comes with buzzing, heat or burning smells, should be checked promptly.
Possible Causes Beyond Normal Startup
An overloaded circuit is a common cause. If a large appliance shares a circuit with lights and outlets, its startup demand may cause noticeable flicker. Some appliances are meant to have their own circuit.
Loose wire connections at outlets, switches, junction boxes or the panel can make voltage drops worse. Problems with the utility supply can also play a role, especially if neighbors notice similar flickering.
Undersized or aging wiring in older homes may struggle with modern appliance loads.
What an Electrician Can Do
An electrician can check whether the appliance and lights share a circuit, measure voltage changes and inspect connections at the panel and along the circuit.
Depending on the cause, solutions may include moving the appliance to a dedicated circuit, repairing connections or addressing service equipment. Do not open the panel or outlet boxes to look for loose wires yourself.
If you see smoke or flames, leave the home and call 911.
If your lights flicker when appliances start, our flickering lights repair page explains how the cause is found and fixed. Contact us to describe which appliances trigger the flicker, and we can help you plan an inspection.