By [AUTHOR NAME, TITLE], Kelley Electrical Contracting. Published 2026-10-16. Last reviewed [DATE]. Educational information, not a substitute for an on-site inspection.
What causes the dip
Air conditioner compressors, well pumps and other motors can draw several times their running current for a moment when starting, which briefly lowers the voltage on shared wiring and dims lights.
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When it is a problem
A big or long dip, lights that flicker repeatedly, tripped breakers, or anything with heat, buzzing or burning smells may indicate loose connections at the panel or meter, wiring that is too small for the load, or a service that is near its limit.
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Fixes
An electrician can inspect connections, check voltage drop, move loads to different circuits, upgrade a panel or service, or recommend soft-start devices that reduce the AC's start-up surge. This matters even more if you plan to add solar, a battery or an EV charger.
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Is it the utility?
If neighbors have it too, or voltage seems to sag at certain times of day, the utility may need to look at the transformer or lines.
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Frequently asked questions
Is it normal for lights to dim slightly when AC starts?
A brief, slight dip can be normal. A large or growing dip is worth inspecting.
What is a soft-start kit?
A device that reduces the surge current when an air conditioner compressor starts. Ask your HVAC contractor.
Could my panel be too small?
Possibly. A load calculation by an electrician can tell you.
Call (559) 940-1939Questions? Talk to a licensed electrician.
Sources and further reading
Need an electrician?
Licensed California electrical contractor, license #1111378. Serving Fresno and Madera.