Half the house has no power.

Press the reset button on every GFCI outlet in the building, including the ones in the garage, the basement, outdoors, and behind furniture. One tripped GFCI takes out every ordinary outlet downstream of it, often in rooms that seem unconnected, and it is the most common explanation by a wide margin.

If that is not it, look at the lights that are still working. If any are unusually bright, unusually dim, or flickering as things switch on and off, stop using the house and call your utility.

Work through it in this order

1. Every GFCI reset. As above. Walk the whole house, including outside and the garage. Push reset firmly on each.

2. The breaker panel. A tripped breaker often sits between on and off. Push each suspect one fully to off, then on. Also look at the main breaker.

3. Double pole breakers. Larger appliances use two adjacent breakers joined together. If one half has tripped it can produce odd partial failures.

4. Any subpanel. Garages, extensions, and workshops sometimes have their own, often with its own main breaker.

5. Ask whether it is really half. Which rooms, which outlets, and which lights. Write it down. It is the first thing an electrician will ask and it narrows the fault immediately.

What each pattern usually means

A run of outlets dead, lights fine: a GFCI upstream, or a loose connection in an outlet box on that run. Outlets are often wired in a chain, so a failure at one kills everything after it.

Lights dead, outlets fine: a lighting circuit breaker or a switch failure.

Roughly half the house dead, the rest working normally: one of the two legs of the incoming supply has failed. That is usually the utility’s side, or the main breaker, or a main lug in the panel. Utility first.

Half dead and the other half behaving strangely: an open neutral, as above. Stop and call.

Everything dead in one room only: one circuit. Breaker or a fault on that circuit. If it keeps tripping, that means something specific.

Why an open neutral matters so much

In a standard US residential supply, two legs share a neutral, and the neutral is what keeps the voltage across each half balanced. If it is lost, the two halves of the house are effectively in series across the full supply voltage, and the split between them is decided by how much is switched on in each.

The practical result: a lightly loaded half sees a much higher voltage than it should. That is what makes the bulbs bright, and it is what burns out electronics, motors, and appliance control boards, sometimes several of them within minutes.

It is also why the instruction is to switch off rather than to investigate. Every minute it stays on costs appliances.

Do not

• Do not keep using the half that works while you wait.
• Do not fit a larger breaker to make something hold.
• Do not open the panel cover.
• Do not assume it will resolve itself. Partial power is usually a connection that is failing, and failing connections get hotter. Any smell of burning changes this to an evacuate and call situation.

Afterwards

If an open neutral or a surge damaged appliances, document it: what failed, when, model numbers, and what the utility or electrician said the cause was. Get their finding in writing.

Damage of that kind is often claimable, and the cause matters to who pays. What a policy does with surge and electrical damage, and if the fault was on the utility’s equipment they may have their own claims process with its own deadline.

The short version

Every GFCI reset button, everywhere, first. Then breakers, including the main and any subpanel. If lights are bright in one part of the house and dim in another, that is a lost neutral: kill the main, stop using the house, and call the utility rather than an electrician.