Half of the house lost power? Here's what's going on, and what to do next

Why does only half of the house lose power?

Hi, I'm Peter, the Master Electrician at PRO Electric plus HVAC. A partial power outage confuses people because it looks random from the living room. The upstairs bathroom is dead, the kitchen outlets on one wall are dead, the garage door won't open, and the TV in the den works fine. Once you know what's behind the panel cover, the pattern makes complete sense.

Almost every home in Fairfax, Loudoun, Arlington, and Prince William Counties gets power through 3 wires from the utility: 2 hot wires and 1 neutral. Electricians call the 2 hots legs, or L1 and L2. Each leg measures 120 volts to the neutral. Across both legs together you get 240 volts, which is what your dryer, range, water heater, and central air conditioner use. This is called split-phase service, and it has been the standard for American homes for decades.

Inside the panel, those 2 legs feed 2 bus bars, and the breakers alternate between them as you go down each column. Your kitchen counter outlets might be on L1, the bedroom lights on L2, the garage on L1, the bathroom on L2. When L2 drops out, everything on L2 goes dark and everything on L1 keeps running. That's what electricians mean by losing a leg of power, and some people call it dropping a phase.

The dim lights deserve a word. With one leg gone, current from the live leg can find a path through a 240-volt appliance and back into the dead leg. The dead half of the house ends up with a weak, unstable voltage instead of nothing at all. That backfeed is unpredictable, which is why I tell people to unplug TVs, computers, and the refrigerator in the affected rooms until it's sorted out.

What to do when half the house loses power: 7 checks in order

Do these in order. The first 6 take about 15 minutes and cover everything a homeowner can safely do. The seventh is the phone call.

Power out in half the house but no breaker tripped: what that usually means

If you did the checks above, every breaker is on, the neighbors have power, and half the house is still dead, the fault is upstream of the breakers. Here is where I find it, roughly in the order I find it:

1. A lost leg on the utility side. A burned or corroded connector where the service drop meets your house, a failed underground service lateral, a bad splice at the transformer, or a blown transformer fuse on one leg only. Your neighbors can be completely fine while you are half dark.
2. The meter. The meter plugs into 4 spring clips called jaws inside the meter base. Jaws lose tension, corrode, and pit over 20 or 30 years. A weak jaw on one leg heats up under load and eventually loses contact. Water getting into an old meter base does the same thing faster.
3. The main breaker. One pole of the 2-pole main fails internally. The handle says on. One side is passing nothing, or passing power through a burned contact that drops out when the AC starts.
4. A loose lug or burned bus bar in the panel. Service conductors that were never re-torqued, aluminum feeders that have crept loose over the years, or a panel with a known bus failure history such as Federal Pacific Stab-Lok or Zinsco.
5. A breaker that is tripped but doesn't look tripped. Some breakers trip to a middle position that is hard to spot at a glance. Push each one firmly to off, then back to on. This also applies to 2-pole breakers feeding a subpanel, which can knock out a whole floor when one pole trips.
6. A failed connection inside a device. A push-in backstab connection on the back of an outlet, or a loose wire nut in a box, opens the rest of that circuit. This usually kills part of one circuit rather than half the house, but on a small home or a townhouse it can look similar.

The common thread is a loose or burned connection. Loose connections make heat, heat makes them looser, and eventually they open. Some let go quietly. Some arc and char the inside of the meter base. In either case, resetting breakers won't bring the power back, because the breakers were never the problem.

When it is one room, not half the house

If a single room or a run of outlets is dead and the breaker is on, the problem is almost always inside that one circuit. The usual causes are a tripped GFCI upstream of the dead outlets, often in a bathroom or garage you didn't think to check, or a failed connection at the first dead outlet in the run. Outlets wired with the push-in backstab holes on the back of the device are the usual suspects, and production builders have used them for decades because they are fast.

Reset the GFCIs, then stop. Opening outlets on a circuit that may still be partly live isn't a homeowner job, and a backstab that failed once has usually scorched the device. We replace the outlet, pigtail the connections under the screws, and check the rest of the run while we are there. If it is an older home, this is also where I start asking about the condition of the home wiring in general.

Whole house out, but the neighbors have power

That's a service problem for your house alone: the main breaker, the meter, the service drop, or the fuse on the utility transformer that feeds you. Check the main breaker once. Then call the utility, then call us. In my experience, when both legs drop at the same time the utility side is the most common cause, and a burned main breaker is the most common cause on your side. I wrote a separate guide for whole house outages: what to check when the power goes out.

Power keeps going out, or goes out for a second and comes back

Two very different problems hide behind this one complaint, and the difference is whether it is only your house.

The whole street blinks and comes back. That's usually a device on the utility line called a recloser doing its job. Something touched the wire, often a branch or a squirrel, the recloser opened for a moment, then closed again once the fault cleared. Annoying, but it's the utility's equipment and the utility's repair. Report it if it becomes frequent, because a line that keeps faulting has a reason.

Only your house blinks, dims, or drops half its power, especially when the AC or dryer starts. That pattern points to a loose connection at the meter, the main lugs, the main breaker, or the service drop. Loose connections open and close as they heat and cool. Every cycle chars the contact a little more, and the intervals get shorter. This is the pattern that ends with a burned meter base. I'd much rather see it while it's still a small repair. Our guide on flickering lights covers the smaller version of this, where one circuit flickers instead of half the house.

Can a partial power outage fix itself, and is it dangerous?

Sometimes the power comes back on its own, and that's part of the problem. A loose or burned connection can open under load, cool down, and reconnect. The lights come back, the damaged connection is still there, and it opens again the next time the AC pulls hard. If the cause is on the utility side, power may return when a fuse is replaced or a splice is repaired, and you may never know it happened. A partial outage that comes and goes on your side always gets worse, never better, because each cycle adds damage to the contact.

The outage itself won't hurt you. The failure behind it can. A loose connection carrying 100 or 200 amps makes real heat, and I have opened meter bases where the plastic had melted around the jaws. An open neutral pushes high voltage into half the house and destroys anything with a circuit board. A dead leg with the air conditioner still calling can damage the compressor, which is the most expensive part of the system. That is the reason for step 2 above: unplug, then call.

Can a bad meter cause a partial power outage?

Yes, and it's one of the more common causes I find in older homes. The meter plugs into 4 spring clips called jaws inside the meter base. Over the years the jaws lose tension, corrode, and pit, and water finds its way into older bases through a cracked hub or a failed seal. One weak jaw on one leg heats up under load and loses contact. You get half the house dead, or half the house flickering when the AC kicks on, and every breaker looks fine.

Ownership matters here. In most Northern Virginia homes, the utility owns the meter itself and the wires to your house, and the homeowner owns the meter base, the service entrance cable, the main breaker, and the panel. Confirm that with your utility when you call, since it can vary by service type. If the base is burned, the repair is ours, coordinated with the utility for a disconnect and reconnect. That is a normal part of our power restoration work, and we handle the scheduling with Dominion Energy or NOVEC so you're not stuck in the middle.

Apartments, townhouses, and mobile homes

Same physics, different access. In an apartment or condo, half the unit dead usually means a tripped breaker in your unit panel or a lost leg in the building's meter stack. Check your own breakers and GFCIs first, then call building management, because the meter room and the feeder to your unit are theirs to open. A townhouse works exactly like a single family home. In a mobile home, the pedestal outside, the post carrying the meter and disconnect, takes weather and vibration for years, and a lost leg at the pedestal is a frequent find.

Questions I get about half the house losing power