Lights often flicker or dim briefly when a large appliance turns on because its motor draws a burst of current as it starts, causing a small, temporary drop in voltage. A quick, slight dip is common, but flickering that is strong, frequent or getting worse may point to an overloaded circuit or a loose connection.
The details of when and where the flicker happens help narrow down the cause.
Why Starting Appliances Affect Lights
Appliances with motors or compressors, such as air conditioners, refrigerators, washing machines, vacuums and sump pumps, need extra current for a moment when they start. That surge of demand can make the voltage dip slightly, and lights on the same circuit or nearby circuits may dim for a split second. This dip usually lasts well under a second. If it lasts longer, or lights stay dim while the appliance runs, the circuit may be carrying more load than it handles comfortably.
LED bulbs can make this more noticeable. Some LEDs react to small voltage changes more visibly than older bulbs, and LEDs on dimmers they were not designed for may flicker even without an appliance starting.
Load and Shared Circuits
If the lights and the appliance share a circuit, the effect is usually stronger. A heavily loaded circuit has less room to absorb the starting surge, so lights may dim more deeply or longer.
When lights throughout the whole home dim each time something starts, the issue may involve the main panel or the service coming into the house rather than one circuit. If neighbors notice the same thing, it may be on the utility side and worth reporting to Rocky Mountain Power. In Utah, summer air conditioning and winter space heater use are common times for homeowners to notice this pattern.
When Flickering May Indicate a Concern
Some patterns deserve a closer look. These include lights that dim sharply or stay dim, flickering that happens with no appliance running, lights that get unusually bright, and flickering that comes with buzzing, warm switches, a burning smell or breakers that trip.
These signs may be related to a loose or deteriorating connection at a device, in the panel or at the service. Loose connections can produce heat, so they should be checked rather than lived with. Do not open the panel or remove switch plates to look for the cause.
How Professional Troubleshooting Helps
An electrician starts by asking which lights flicker, which appliance seems to trigger it and whether the pattern has changed. From there, the affected circuits, connections and loads can be checked to see whether the flicker is normal behavior or a sign of a fault.
If the flickering in your Salt Lake City home is getting worse or comes with other warning signs, our electrical troubleshooting services can find the cause and recommend the right fix.