How to Stay Warm in a Japanese Apartment: Heating Options and What They Cost
Japanese apartments are often poorly insulated and have no central heating, so heat yourself, not the whole room. An electric blanket or heated carpet costs only a few yen an hour, while an air conditioner heating a whole room costs much more. Add insulating film to single-glazed windows, use thick curtains, and run a humidifier, because heated winter air in Japan becomes very dry.
Running cost: a quick way to compare
Electricity cost per hour is roughly: watts ÷ 1,000 × the price per kWh. Japan's industry guideline uses ¥31 per kWh as a typical rate; your own contract may differ.
At ¥31/kWh, a 50 W electric blanket costs about ¥1.6 an hour. A 300 W kotatsu heater at full power costs about ¥9 an hour, though its thermostat cycles on and off. An air conditioner heating a room may draw several hundred to over 1,000 W, or roughly ¥15–30 or more an hour.
Options compared
- Electric blanket (電気毛布): the cheapest way to sleep warm.
- Heated carpet (ホットカーペット): warms you from the floor while sitting; sized in tatami (1畳, 2畳, 3畳).
- Kotatsu (こたつ): a heated table with a quilt — very efficient for sitting and working. See our kotatsu guide.
- Air conditioner (エアコン): heats the whole room; best combined with the others on a low setting.
Keep the heat in
- Window insulation film (窓 断熱シート) on single-glazed glass reduces cold radiating into the room.
- Thermal or blackout curtains that reach the floor help as much as a heater on cold nights.
- Humidifier (加湿器): Japanese winter air is dry, and humid air feels warmer at the same temperature.
Safety
Do not sleep with a kotatsu or heated carpet on high for hours, and keep heaters away from curtains and futons. Many products have an auto-off timer (切タイマー) — use it.
Picks with checked prices
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Heated carpet (2 tatami)
日本製 ホットカーペット 2畳 本体 175x175cm 通常タイプ / 省電力タイプ【 ホットカーペット2畳用サイズ 電気カーペット 電気カーペット2畳 本体
¥6,380（すまいのコンビニ · checked 2026-10-24）
Why this one: Warms you from the floor while you sit; heating only half the area saves power.
Check on the item page: 2畳 = about 176×176 cm. 面切替 = heat half or the whole area. ダニ対策 = dust-mite mode. 本体 = the heated base (a cover may be sold separately).
View on RakutenOther price levels: Budget ¥4,480Premium ¥16,900
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Window insulation film
＼連続楽天1位・1,424件レビュー突破！／ Masinca 遮光シート 窓 真っ黒・100%遮光率 完全遮熱シート ぐっすり眠れる 超遮光 420dオックスフ
¥1,077（スマイルライフショップ · checked 2026-10-24）
Why this one: Cuts the cold coming off single-glazed windows; most types peel off without marks when you move out.
Check on the item page: 断熱シート = insulation sheet. 貼ってはがせる = removable. 結露防止 = reduces condensation.
View on RakutenOther price levels: Budget ¥950Premium ¥3,780
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Steam humidifier
2H限定50％OFFクーポン！【年間ランキング受賞】 加湿器 大容量 加湿器 卓上 6L 加湿機 ハイブリッド加湿器 加湿器 スチーム式 四重除菌 空気清浄機
¥13,980（春夏秋冬 · checked 2026-10-24）
Why this one: Japanese winter air is dry; steam types boil water, so they stay hygienic with little cleaning.
Check on the item page: スチーム式 = steam type (hygienic, uses more power). 超音波式 = ultrasonic (cheap to run, needs cleaning). 適用畳数 = room size it covers.
View on RakutenOther price levels: Budget ¥4,080Premium ¥27,500
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Electric blanket
【期間限定価格〜10/31 9:59迄】電気毛布 電気敷毛布 電気掛敷毛布 敷き 掛け敷き 丸洗い 洗える ダニ対策 温度調節 省エネ 節電 YMS-40 YM
¥2,980（くらしのeショップ · checked 2026-10-24）
Why this one: About ¥1.6 an hour at 50 W — the cheapest way to sleep warm.
Check on the item page: 掛け敷き兼用 = use over or under you. 洗える = washable. 切タイマー = auto-off timer.
View on RakutenOther price levels: Budget ¥3,100Premium ¥12,900
FAQ
- What is the cheapest way to stay warm in a Japanese apartment?
- Heat yourself, not the room: an electric blanket costs about ¥1.6 an hour at 50 W and ¥31/kWh, far less than an air conditioner heating the whole room.
- Why is my Japanese apartment so cold?
- Many apartments have little insulation, single-glazed windows and no central heating. Insulating film, floor-length curtains and personal heaters help a lot.