What Actually Causes a Lost Leg of Power?

This is one of those electrical problems that confuses homeowners because the panel itself looks totally normal. The issue almost always lives outside the house or right at the point where power enters it.

Problems at the Weatherhead and Service Entrance

The service entrance cables that run from the utility pole down to your weatherhead can corrode, loosen, or get physically damaged over time. A loose connection at the weatherhead is surprisingly common in older homes, especially after ice storms or heavy wind. That loose contact can drop one leg of power entirely, or cause it to fluctuate, which explains why some appliances that need 240 volts (like your dryer, HVAC unit, or range) stop working even though the lights on that circuit looked fine a minute ago.

Utility Transformer or Meter Problems

Your electric utility transformer supplies the two legs. If it fails or one leg drops at the transformer, that’s completely out of your hands. Call your utility company first in this situation. They own everything up to and including the meter, so they’re responsible for diagnosing and fixing it at no charge to you. The ComEd outage and service line covers most of the southwest suburbs, and they can usually tell you over the phone whether there’s a known issue on your street.

When the Problem Is Inside Your Panel

If the utility confirms their lines are fine, the issue may be a failed main breaker or a loose bus bar connection inside the panel itself. A double-pole main breaker can partially fail, dropping one leg while the other keeps feeding circuits. This is less common than a utility issue, but it happens. It also carries real danger since a partially working main breaker may not trip properly under overload. A licensed electrician needs to inspect this. Do not try to open the main panel cover and poke around on your own, especially near the service entrance lugs, which stay energized even when your main breaker is off.

How to Diagnose It Safely Before Calling for Help

You can do a quick check without touching anything inside the panel.

Look at Which Circuits Are Dead

Walk through the house and note a pattern. If the dead outlets and fixtures seem to alternate room by room, or if 240-volt appliances are completely dead while other things work, that points strongly to a lost leg. If it’s more random, the problem could be something else entirely, like a tripped GFCI somewhere upstream. Our post on whether your panel needs an upgrade covers some of the other warning signs worth watching for.

Check Your Meter Pan Visually

Stand outside and look at your electric meter. If it’s blank or showing zero, you likely have no power at all from the utility. If it’s reading normally, power is reaching the meter, meaning the problem is between the meter and your panel, or inside the panel itself. At that point, call a licensed electrician. For homeowners around the Palos Hills area, this kind of electrical inspection is straightforward for a pro to diagnose with a multimeter in a few minutes.

The bottom line: half-power situations are almost never a DIY fix. They involve either utility infrastructure or the highest-voltage parts of your home’s system. Getting it wrong means potential damage to appliances, a fire risk, or a shock hazard. If your utility rules out their side of the line, reach out to a local electrician to pick it up from there. Reed Electrical Services works throughout the southwest Chicago suburbs and can walk through this kind of diagnosis quickly. You can see more about what we handle on the full services page.

For more background on electrical safety standards and wiring requirements, the NFPA 70 National Electrical Code is the industry reference electricians follow when evaluating service entrance and panel issues.

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