Blackout preparedness: how to get ready for a long power cut

To prepare for a blackout, store at least 3 days of water (1 gallon or about 3.8 litres per person per day, per the CDC) and no-cook food, keep torches with spare batteries, a battery or wind-up radio, a charged power bank and some cash, and plan how you will stay warm without heating. Fit a battery-powered carbon monoxide alarm, never run a generator or camp stove indoors, ask your doctor how to manage any powered medical devices or refrigerated medicines, and keep the fridge and freezer shut when the power goes.

A blackout is a large, long power cut that takes out a district, a city or a whole country. On 28 April 2025, almost all of Spain and Portugal lost power and restoration ran into the next day. Trains, metros, traffic lights and card payments all stopped.

The Polish government’s Safety Guide warns that a power cut “may last several days”. Without power, heating, internet and mobile networks can fail, and in many buildings so can the water.

Blackout supplies checklist

Item	Why	How much
Bottled water	drinking, cooking, hygiene	1 gal / 3.8 l per person per day × 3 days
Torch or headlamp	light without fire risk	1 per person + spare batteries
Battery or crank radio	official updates without internet	1 per household
Power bank	phone, USB light	fully charged
No-cook food	tins, crackers, nuts, bars	3 days
Camping stove + gas	a hot meal, boiling water	outdoors only (Ready.gov)
Cash	when cards fail	small notes
Warm layers, blankets, sleeping bags	winter heat loss	for everyone
Medication	continuity of care	at least a week
First aid kit	minor injuries	1 per household
Fridge and freezer thermometers	to judge food safety	1 each
Carbon monoxide alarm (battery or battery backup)	an invisible, odourless gas	near sleeping areas

For how to store and rotate water and food, see our water and food supply guide. For a medical kit, see the first aid kit checklist.

Before a power cut

Ready.gov and FEMA suggest these steps while the lights are still on:

Medical devices and medicines. Talk to your doctor about how you will power medical devices and keep refrigerated medicines cold during an outage.
Thermometers. Put one in the fridge and one in the freezer, so after an outage you can check temperatures instead of guessing. Have ice or frozen gel packs ready.
Carbon monoxide and smoke alarms. Fit alarms with battery backup on every level of your home and near sleeping areas.
Surge protection for computers and other electronics.
A heat and cold plan. Decide where you could go for warmth in winter or cooling in a heatwave.
Supplies and a paper plan. Keep several days of supplies and a paper copy of your contact numbers. Our family emergency plan shows what to include.
Charge and fuel. Keep phones charged and the car’s tank full before forecast storms.

In the UK, the government suggests signing up to the Priority Services Register for extra help during supply interruptions, and reporting a power cut on 105 (England, Scotland and Wales).

The first hour

Check whether it is just you (the fuse box) or the whole building and street.
Unplug electronics such as the computer, TV and washing machine, as the Polish guide and Ready.gov advise, because the power surge on restoration can damage them. Leave one lamp switched on so you know when power returns.
Fill the bath, pots and bottles while there is still pressure.
Note the time the power went off. It is your starting point for the fridge and freezer.
Turn on the radio and follow official updates.
Switch your phone to battery saver. Text rather than call.
Call emergency services only if life or health is at risk. Unnecessary calls block the lines.

Keeping food safe: fridge and freezer

FoodSafety.gov (USDA, FDA and CDC) gives these times, as long as the doors stay closed:

Appliance	Safe for about	Safe temperature
Fridge	4 hours	40°F (4°C) or below
Full freezer	48 hours	0°F (−18°C) or below
Half-full freezer	24 hours	0°F (−18°C) or below

Keep the doors shut. Every opening shortens these times.
After 4 hours without power, move the perishables you want to keep into a cooler with ice.
Ready.gov advises throwing out perishable food such as meat, poultry, fish, eggs and leftovers that has been above 40°F (4°C) for two hours or more.
Thawed food can be refrozen if it still has ice crystals or is still as cold as a fridge.
Do not store food outdoors or in snow, Ready.gov says. Outdoor temperatures change, and sun can warm food quickly.
When in doubt, throw it out. You cannot judge safety by smell.

Our guide to food safety in a power outage covers which foods to keep and which to bin.

Water during a blackout

The CDC notes that water treatment systems may not work fully during an outage. Follow any boil-water notice from your water company or local authority, and drink, cook and wash with bottled, boiled or treated water when told to.

Staying warm safely

The UK government warns that homes can become cold very quickly when the heating goes off. The CDC’s advice:

Have at least one safe source of warmth: extra blankets, sleeping bags and warm coats for everyone.
Use fireplaces, wood stoves and space heaters only as the manufacturer instructs, and only if they are installed to code. Check with your local fire service before using a kerosene heater, as they are illegal in some places.
Gather everyone in one room, ideally a sunny one. Cover the windows at night, dress in layers, and wear a hat.
Never heat your home with a gas oven or hob, a barbecue or a camp stove.
If it gets too cold, go to a friend’s home or a public warming centre.

A body temperature below 95°F (35°C) means hypothermia, which the CDC calls a medical emergency. Get medical help immediately.

In a heatwave

Without air conditioning, the CDC suggests spending a few hours in a cooled public place such as a library or shopping centre, taking cool showers, and not relying on fans alone when it is very hot. Heat stroke is the most serious heat illness and needs emergency care.

Carbon monoxide: the main danger

Carbon monoxide (CO) is a gas you cannot see or smell, produced by generators, camp stoves, barbecues and car engines. During an outage it is tempting to use them indoors. Do not.

Rules from the CDC and Ready.gov:

Never use a generator, camp stove, barbecue or charcoal grill inside your home, basement or garage, even with doors and windows open.
Run generators outdoors, more than 20 feet (about 6 m) from windows, doors and vents.
Never leave a car running in a garage.
Fit battery-powered or battery-backup CO alarms near every sleeping area, check the batteries when the clocks change, and replace the alarm every 5 years or as the maker instructs.

Symptoms (CDC): headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion. They are often described as flu-like. People who are asleep or have been drinking can die before they notice anything.

If you suspect CO: get everyone into fresh air at once and call your emergency number (the CDC lists 911 or Poison Control in the US).

Medical devices and refrigerated medicines

If anyone at home relies on oxygen, a ventilator, a powered wheelchair, a dialysis machine or medicines that must stay cold, plan this first.

Ask your doctor how to power devices and store medicines during an outage, as Ready.gov advises.
Know your backup. The Red Cross advises learning how to connect and start backup power, and knowing how long it will last. Keep a manual wheelchair if the person uses a powered one.
Register with your electricity provider if a household member depends on powered equipment, as the Red Cross suggests. In the UK this is the Priority Services Register.
Refrigerated medicines: the CDC says to replace them if the power has been out for a day or more, unless the label says otherwise. If a medicine is life-sustaining, keep using it until a new supply is available, and ask your pharmacist.

Risks specific to flats

Water. Upper floors often rely on electric pumps. Fill the bath and pots as soon as the lights go out.
Lifts. Avoid them during storms and rolling outages. Plan how older neighbours on high floors will use the stairs.
Heating. Central heating depends on electric pumps. In winter a flat cools within hours.
Entry phones and garage doors stop working. Carry a physical key.

If it lasts more than a day

Food. Eat from the fridge first, then the freezer, then your stored supplies.
Cooking. Use a camping stove outdoors only; see our camping stove guide.
Light. Use battery lights. If you must use candles, the CDC says to keep them away from anything that can burn and never leave them unattended.
Neighbours. Check on older neighbours: water, medication, warmth.

Generator, power station or power bank?

In a flat a fuel generator is out: never run one indoors, on a balcony or in a stairwell. Power banks for phones and USB lights, or a portable power station for bigger needs, are the sensible choice. In a house, a generator can make sense, but only outdoors at least 20 feet from openings, with fuel stored safely. Ready.gov suggests deciding in advance what you will plug in, as you may not be able to power everything at once.

After the power returns

Check fridge and freezer thermometers before eating anything. When in doubt, throw it out.
Replace refrigerated medicines that were warm for a day or more.
Never touch a fallen power line, the CDC warns, and do not drive through water that may contain one.
Restock batteries, water and food, and recharge every power bank.

Before the lights go out

Thirty minutes today does most of the work: test torches and batteries, charge a power bank, put some cash aside and buy a pack of water. The rest you can add over time. If you rent, our guide for renters covers small-space storage.

FAQ

How long can a blackout last?

Most outages end within hours, but large ones can last longer. The Polish government guide warns a power cut may last several days, so plan water, food and light for at least 3 days.

Will I have running water during a blackout?

Not always. Many buildings pump water to upper floors electrically, and water utilities have limited backup power. Keep bottled water: the CDC recommends 1 gallon (3.8 l) per person per day.

Can I run a generator in an apartment?

No. Fuel generators produce carbon monoxide and must never run indoors, on a balcony or in a stairwell. The CDC says to run them outdoors, more than 20 feet (about 6 m) from windows, doors and vents. In a flat, use power banks or a portable power station.

How long does food last in the fridge during a power cut?

About 4 hours if the door stays closed, according to FoodSafety.gov. A full freezer holds a safe temperature for about 48 hours and a half-full one for about 24 hours.

What are the symptoms of carbon monoxide poisoning?

The CDC lists headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion, often described as flu-like. People who are asleep can die before they notice symptoms. Get everyone into fresh air and call the emergency number.

What should I do with insulin or other refrigerated medicines after a blackout?

The CDC says to replace refrigerated medicines if the power has been out for a day or more, unless the label says otherwise. If a medicine is life-sustaining, keep using it until you get a new supply, and ask your pharmacist or doctor.

Sources

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This guide is educational. In an emergency, follow official alerts and first responders.