What causes partial power loss in a house?
Partial power loss — where some lights and outlets work but others don't — is almost always caused by a tripped breaker, a blown fuse, or a lost 'leg' of power from the utility. In Florida, partial power loss after a storm often means one of the two 120-volt legs from the utility pole has been damaged. If resetting breakers doesn't restore power, call your utility company first, then an electrician if the problem is inside your panel.
- ›Tripped breaker — check your panel and reset any tripped breakers
- ›Lost utility leg — one of two 120V lines from the pole is down
- ›Loose main breaker connection — causes intermittent partial power
- ›Damaged service entrance cable — common after storms
- ›Faulty double-pole breaker — affects 240V circuits like dryers and AC
What Is Partial Power Loss?
Partial power loss — where some circuits in your home work and others don't — is a distinct electrical problem that's different from a complete outage. In most cases, it's caused by what electricians call a 'lost leg.' Understanding how your home's electrical service works helps explain why this happens.
How Your Home's Electrical Service Works
Your home receives power from the utility company via a service entrance — typically two 120V 'legs' (or phases) that together provide 240V for large appliances, and individually provide 120V for standard circuits. Your electrical panel distributes these two legs across your circuits — some circuits are on Leg 1, some on Leg 2, and 240V appliances (dryer, HVAC, water heater) use both legs. When you lose one leg, all the circuits on that leg go dark while the other leg's circuits continue to work normally.
Common Causes of Partial Power Loss
Here are the most common causes of losing one leg of electrical service:
Tripped Main Breaker (One Pole)
Your main breaker is a double-pole breaker that controls both legs. If one pole trips (which can happen with some breaker designs), you'll lose half your circuits. Check your main breaker — if it's not fully in the 'on' position, try resetting it. If it trips again, call an electrician.
Failed Utility Connection
The utility company's connection to your home — at the weatherhead, meter, or service entrance — can fail or become loose. A loose utility connection is a utility company problem, but it can also be a problem at your meter base or service entrance that requires an electrician. Call both your utility company and an electrician.
Damaged Service Entrance Wiring
The wires running from the utility connection into your panel can be damaged by weather, animals, or age. Damaged service entrance wiring requires immediate professional repair.
Failed Transformer
If the utility transformer serving your home fails, you may lose one or both legs of power. This is a utility company problem — call Duke Energy or SECO Energy.
What to Do If You Have Partial Power Loss
First, check your main breaker — make sure it's fully in the 'on' position. If it's tripped, reset it. If it trips again immediately, don't keep resetting it — call an electrician. Next, check whether your neighbors have power. If it's a neighborhood-wide outage, call your utility company. If only your home is affected, call both your utility company and an electrician, as the problem could be on either side of the meter.
Is Partial Power Loss Dangerous?
Partial power loss can be dangerous in specific situations. If the cause is a loose connection — at the utility connection, meter, or service entrance — that loose connection can arc and cause a fire. Don't ignore partial power loss or assume it will resolve on its own. Get it diagnosed and repaired promptly.