The short answer: don’t try to heat the whole flat. Heat the people and a single room. Dress in layers, gather the family in the smallest, best-oriented room, block draughts and use blankets and sleeping bags. A well-sealed flat loses few degrees in the first hours. The danger isn’t one cold night: it’s carbon monoxide from whatever gets lit indoors to keep warm.
- First, keep the heat in: windows, shutters and doors closed from the first minute.
- One room only: the smallest, interior or sunny one, with the door shut.
- Heat the body, not the air: layers, hat, wool socks, blankets and a sleeping bag.
- Never use the oven, the gas hob, a barbecue, a camping stove or a generator to keep warm.
- A battery-powered carbon monoxide detector if you use any flame or combustion indoors.
Step 1: don’t let the heat you already have escape
When the power goes, your flat still holds the heat from the heating, the walls and the furniture. The goal in the first hours is to lose it as slowly as possible.
- Lower the shutters (persianas) and draw the curtains as soon as it gets dark. In the daytime, raise them only on the windows that get sun.
- Close the doors of rooms you’re not using: that way you don’t have to heat them.
- Seal the gaps around doors and windows with draught excluders, rolled towels or a long cushion.
- Cover the glass with a blanket or an emergency foil blanket (silver side facing in) if the window is large or old.
- Don’t open the fridge or the balcony unless you have to: every opening cools things down.
Step 2: choose a “refuge” room
It’s much easier to keep a 10 m² room with several people in it at 17-18 °C than a 30 m² living room. Each person gives off heat, roughly like an old 100 W light bulb.
| Better | Worse |
|---|---|
| Small room, interior or south-facing | Large living room with big windows |
| With a rug and few walls facing the street | Cold floor and exterior walls |
| Everyone together with the door shut | Everyone in their own room |
Put a rug or blankets on the floor, especially if children are playing there. Bring what you’ll need into the refuge (water, torch, radio, food) so you’re not coming and going and opening doors.
Step 3: heat the people, not the air
- Layers: thermal top, fleece and a jacket on top. Several thin layers are warmer than one thick one.
- Head, hands and feet: hat (for sleeping too), gloves and wool socks. A lot of heat is lost there.
- Move a little every so often: going up and down the stairs or doing squats warms you more than any blanket.
- Eat and drink something hot: the body needs “fuel”. A hot drink in a flask lasts for hours.
- Hot water bottles: if you have a gas hob or a stove, heat water only for as long as needed, with ventilation, and keep it in a flask and in hot water bottles. A bottle at the foot of the sleeping bag changes the night.
- For sleeping: a sleeping bag inside the bed, or several blankets underneath as well as on top: the cold comes mostly from the mattress.
- Dry clothes: damp or sweaty clothes cool you down very quickly. Change them.
Step 4: if you have a battery, use it for an electric blanket, not a heater
An electric heater uses 1,000-2,000 W: it would drain a 1 kWh portable battery in under an hour. An electric blanket or bed warmer uses about 60-100 W, so the same battery lasts all night. Heating the body and not the room is, once again, what works.
If you’re thinking of getting one, there’s a comparison in portable power stations and solar panels for a flat and you can work out how much you need with the battery calculator.
What you must never do
| Don’t use | Why |
|---|---|
| The oven or gas hob to heat the home | They produce carbon monoxide and aren’t designed to be on for hours |
| A barbecue, charcoal brazier or wood indoors | The most typical cause of serious poisoning |
| Camping stoves and heaters | They’re designed for outdoors, even if you open the window |
| Petrol generators indoors, on an enclosed balcony or in the garage | The gas gets in through windows and vents: always outside and far away |
| Candles as heating | They barely heat and are the number one fire risk in a blackout |
What about a butane heater?
Many Spanish homes have an infrared or catalytic butane heater (estufa de butano). It’s approved for indoor use and doesn’t need electricity, so it can be a real help, as long as:
- It’s in good condition and has an oxygen depletion safety system (modern ones do).
- You use it in a large room with some ventilation: a window slightly open.
- You never leave it on in the bedroom while you sleep or use it in the bathroom.
- You have a battery-powered carbon monoxide detector in the same room.
- No clothes drying on it and no furniture within a metre.
Watch out for hypothermia
Older people, babies and people with limited mobility get cold sooner and notice it less. Watch for intense shivering, clumsiness, slow speech, drowsiness or confusion, and in babies, cold skin and very little energy. If they appear, wrap the person up, give them a hot drink (no alcohol) and call 112. There are more ideas for them in kits by profile.
If the cut drags on and it’s no longer bearable at home, don’t hold out out of pride: go to family or friends who have power, or ask your town hall (ayuntamiento) about the warm spaces that open in these situations.
What to have at home before winter
| Item | What for | Price |
|---|---|---|
| Battery carbon monoxide detector | Warns you if something you light causes problems | € |
| Emergency foil blankets | Cover windows, go under a normal blanket | € |
| Winter sleeping bag | Sleep warm without heating | €€ |
| Hot water bottles and a flask | Heat for hours without electricity | € |
| Thermal clothing and wool socks | The first layer of everything | € |
| Draught excluders for doors and windows | Stop draughts (and save all winter) | € |
Approximate price range: € under €40, €€ €40–80. The real price is whatever Amazon shows.
Battery-powered carbon monoxide detector
Best for: any home with a butane heater, fireplace or gas boiler.
- Runs on batteries: keeps warning you without power
- Loud audible alarm
- Look for compliance with EN 50291
Emergency foil blankets
Best for: insulating windows and adding warmth under normal blankets.
- Weigh almost nothing and take up very little space
- Reflect body heat
- Multi-packs for a few euros
Winter sleeping bag
Best for: sleeping well even if the flat drops below 15 °C.
- Look at the comfort temperature, not the extreme one
- A 0 °C comfort rating is more than enough indoors
- Also good for camping
Hot water bottle with cover
Best for: warming the bed or your feet for hours.
- Natural rubber or thermoplastic, 2 litres
- With a cover so you don’t get burnt
- Don’t use boiling water: very hot, but not bubbling
Draught excluders for doors and windows
Best for: flats with old windows or doors with a gap.
- Self-adhesive and easy to fit
- You’ll notice the difference on your bill too, even with power
Keeping warm is one part of the 72-hour kit. And if you want to go over everything to do when the power goes, see what to do in a blackout, step by step.
Sources: CDC, “What to Do to Protect Yourself During a Power Outage”; EPA, “Power Outages and Indoor Air Quality”.