Power outages are hard on a house in two ways. The obvious one is the hours without lights, cooling or refrigeration. The less obvious one is what happens when the power comes back: it rarely returns cleanly, and the brief surges, dips and flickers in the first minutes can damage compressors, control boards and electronics that survived the outage itself. Ready.gov's advice is to unplug appliances and electronics during an outage for exactly that reason.
This checklist covers what to do when the power goes out, what to check before you turn things back on, and the signs afterward that mean something needs a technician. None of it involves opening a panel or touching wiring; anything that points to the electrical system itself is an electrician's call.
When the power goes out
The first ten minutes decide whether the restoration damages anything. Turn off or unplug the things that are expensive and sensitive, and leave the refrigerator and freezer closed. The U.S. CDC's guidance is that a closed refrigerator keeps food safe for about four hours and a full freezer for about 48 hours, so the clock starts now.
- Turn the thermostat to off so the air conditioner or heat pump does not try to start on unstable power when it returns.
- Unplug computers, TVs, game consoles and anything with a control board you care about, or switch off their surge protectors.
- Leave the refrigerator and freezer doors closed, note the time the power went out, and leave one light switched on so you know when power returns.
- If you run a generator, keep it outdoors at least 20 feet from the house with exhaust pointed away, and plug appliances directly into it or through a transfer switch. Never plug a generator into a wall outlet.
Before you turn things back on
When the lights come back, wait. Give the power a few minutes to settle, and watch for flickering. If lights are dim, unusually bright or pulsing, the supply is not stable; leave major appliances off and call the utility. Once the lights have been steady for several minutes, bring things back in stages rather than all at once.
- Wait several minutes with steady lights, then plug in electronics first, small appliances next, and the big loads one at a time.
- Turn the thermostat back on last, after everything else is running normally. Many systems have a built-in delay before the compressor starts; that is normal.
- If any outlet, switch or appliance was wet or in standing water, do not use it. FEMA's guidance is that water-damaged equipment should be inspected by a qualified technician before it is energized.
The refrigerator and freezer
The CDC's rule is simple: perishable food in a refrigerator that has been without power for more than four hours should be thrown out, unless you added ice or another cold source. Frozen food that still has ice crystals or reads 40 degrees Fahrenheit or below can be refrozen or cooked; anything that fully thawed and warmed should go. An appliance thermometer in each compartment takes the guesswork out of it.
- Check the thermometer if you have one. Above 40 degrees in the refrigerator for more than two hours is the discard line for most perishables.
- Discard meat, poultry, fish, eggs, milk, soft cheese, cut produce and leftovers after four hours without a cold source. Never taste food to decide.
- After restarting, give the refrigerator a few hours to come back to 40 degrees before restocking, and listen for a compressor that runs continuously or does not start.
Air conditioner, heat pump and water heater
The compressor in an air conditioner or heat pump is the most expensive single thing in the house to replace, and it is the part most vulnerable to a hard restart on dirty power. Give it time, and if it does not start or sounds different, do not keep trying. A water heater usually restarts on its own; a gas heater with a standing pilot may need the pilot relit per the instructions on the unit, and an electric heater simply resumes.
- After the thermostat is turned back on, expect a delay before the outdoor unit starts. If it hums without the fan spinning, or clicks on and off repeatedly, turn it off and call an HVAC technician.
- If the breaker for the AC tripped during the outage, reset it once. If it trips again, leave it off and call.
- Check for hot water after an hour or so. On a gas heater, follow only the printed relighting instructions, and call the gas utility if you smell gas.
Signs that mean call someone
Most houses come back without incident. These are the exceptions. Anything involving the panel, outlets or wiring is an electrician; a single appliance that will not restart is an appliance technician; the AC or furnace is an HVAC company; and a smell of gas is the gas utility, from outside the house.
- Lights that stay dim or flicker, or some circuits dead while others work: call the utility first, then an electrician if the utility says the supply is fine.
- A breaker that trips repeatedly after being reset once.
- A burning or hot-plastic smell from any outlet, switch or the panel: turn off the circuit at the breaker if you can do so safely and call an electrician.
- An appliance that shows an error code, will not power on, or runs but does not heat or cool, and anything that was wet.
Questions people ask
The power came back but the AC will not start. What now?
Check the thermostat is set to cool and give it ten minutes; many systems have a startup delay. Check the breaker and reset it once if it tripped. If the outdoor unit hums, clicks or stays silent after that, leave it off and call an HVAC technician. Repeated restart attempts can damage the compressor.
How do I know if frozen food is still good?
If it still has ice crystals or an appliance thermometer reads 40 degrees or below, it can be refrozen or cooked. Fully thawed food that warmed above 40 for more than two hours should be discarded. A full freezer that stayed closed holds for about two days; a half-full one about one.
Is a power strip enough surge protection?
A plain power strip provides none; look for one labeled as a surge protector. For the AC, water heater and other hardwired equipment, only a panel-mounted whole-home surge protector helps, and an electrician installs it.