A winter power cut turns the whole problem of staying comfortable into a problem of staying warm. In September 2018, the Hokkaido Eastern Iburi earthquake (北海道胆振東部地震) knocked out power across the entire island at once, and homes lost heating along with the lights. The season was mild that week, but the event made the general lesson clear: an outage can be regional, it can last more than a day, and your heat can vanish with your electricity. Planning ahead is calm, ordinary preparation, not cause for alarm.
Warmth comes from layers and insulation first
Before you reach for any heater, trap the warmth you already have. Dress in several thin layers rather than one thick one, and keep your head, neck, and feet covered. A sleeping bag rated for cold weather, or a nest of blankets and a duvet, holds body heat far better than sitting in an open room. If you have a pop-up tent, setting it up indoors creates a small pocket of air that your body warms quickly, which is especially useful for children. Gather everyone into one room and close the doors to the rest of the home so the heat you generate stays in one place.
A hot water bottle is one of the most efficient tools you can own. Warm water on a gas stove, fill the bottle, wrap it in a towel, and it will radiate gentle heat for hours inside a sleeping bag. A few of these can keep a family comfortable overnight without any heater running at all.
Kerosene and gas heaters: useful, but ventilate
Portable kerosene stoves (石油ストーブ) and cassette-gas heaters produce strong heat without electricity, which makes them valuable in a blackout. They also consume oxygen and release carbon monoxide, a gas you cannot see or smell. The single rule that matters most: never sleep with an unvented combustion heater running. Carbon monoxide poisoning happens quietly, often while people are asleep in a sealed room.
Use these heaters only while you are awake and able to monitor them. Crack a window on two sides of the room every hour to bring in fresh air, even though it feels wasteful. Keep the heater well clear of bedding, curtains, and futons, and place it on a stable, level surface where it cannot be knocked over. A battery carbon-monoxide alarm is inexpensive and worth having. Turn combustion heaters off completely before you settle down to sleep, and rely on layers and hot water bottles through the night instead.
Warming food and drink
A hot meal does more for morale and body temperature than its size suggests. A single cassette-gas burner (カセットコンロ) lets you boil water for tea, instant soup, or noodles, and heat canned food. Keep a spare gas canister or two. Warm drinks spaced through the day are a simple, steady way to stay comfortable.
Where a portable power station fits
People often assume a portable power station can run a heater. For most electric heaters, it cannot. A ceramic fan heater or oil-filled radiator typically draws 1,000 to 1,500 watts, which will drain even a large battery station in under an hour and may exceed its output limit entirely. Power stations are better understood as tools for the small, essential loads: charging phones, running a light, keeping a modem alive, or briefly powering a low-wattage electric blanket if the unit's rating allows it. Match the device to the station's real limits rather than expecting it to heat a room.
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A calm plan beats a cold scramble
Stock a cold-rated sleeping bag or extra blankets, a couple of hot water bottles, a cassette burner with spare gas, and, if you choose to keep a combustion heater, a carbon-monoxide alarm to go with it. Store them where you can reach them in the dark. Winter outages are manageable when the warmth plan is set before the power goes out. While you are thinking about winter safety at home, it is also worth checking that heavy furniture is secured, since many outages follow earthquakes; see our guide to anchoring furniture.