Why Your Lights Flicker When the A/C Turns On — and How to Fix It

It’s a hot summer day. You turn on the A/C… and the lights in your house flicker for a moment.
Is it normal? Is it harmless? Or is it a sign that something's wrong?

Flickering lights when your air conditioner starts up is more common than you think — but it’s not something to ignore. In some cases, it’s a warning that your electrical system is under stress or even unsafe.

Here’s what causes this flicker, when it’s a problem, and how to fix it for good.

🌬️ Why Does My A/C Make the Lights Flicker?

When your A/C unit turns on, it draws a high amount of current in a short burst — known as “inrush current.” That momentary surge can cause a slight voltage dip throughout your home, making lights dim or flicker.

This is especially common with:

• Older or oversized A/C units
• Undersized wiring
• Shared circuits
• Panels close to max capacity

While a quick, single flicker is often harmless, repeated dimming, flickering, or buzzing is usually a red flag.

🚨 When It’s a Sign of a Bigger Problem

If your lights do any of the following when the A/C runs, it’s time to call a licensed electrician:

• Flicker continuously or more than once
• Stay dimmed longer than a second
• Flicker throughout the entire house
• Cause buzzing or humming from switches or outlets
• Trigger breaker trips or overheating

These signs could point to overloaded circuits, poor grounding, outdated panels, or wiring issues — all of which can be dangerous in the summer heat.

✅ How to Fix It

Here’s what we recommend to stop flickering and protect your home:

✔️ Install a Dedicated Circuit for Your A/C
Your air conditioner should have its own circuit, separate from lighting or other major appliances. This prevents it from stealing voltage from the rest of your home.

✔️ Upgrade or Replace Old Panels
If your panel is old, outdated, or full, it might not have the power capacity to support modern A/C systems. Upgrading your panel gives your home the room and stability it needs.

✔️ Check for Loose or Failing Connections
Sometimes flickering is caused by loose terminals or worn wiring. Heat expands metal, which can worsen loose connections. A full inspection can catch these risks early.

✔️ Install a Soft Start Device
Some A/C systems allow for a “soft start” upgrade that reduces the initial inrush current, so lights won’t flicker when it kicks on. Ask your HVAC technician or electrician if this is an option.

✔️ Balance the Load Across Circuits
If your electrical load isn’t balanced properly across phases in your panel, it can cause dips when large appliances run. We can assess and rebalance for smoother power flow.

💡 Bonus Tip: Consider Whole-Home Surge Protection

That initial voltage dip can also lead to power surges when your system compensates. A whole-home surge protector defends your electronics from unexpected voltage spikes caused by heavy summer use.

🏠 Don’t Let Flickering Lights Become a Fire Hazard

Flickering lights might seem like a minor annoyance, but they’re often the first sign of an overloaded or strained system. And in the summer heat, your electrical system is already working overtime.

At E&A Electric LLC, we specialize in diagnosing and fixing flickering, overloaded panels, and A/C-related issues — quickly and safely.

📞 Call now to schedule a summer safety inspection or panel evaluation.
Let’s keep your home cool and stable this season.