Heaters ranked
by cost
per hour
But heaters that warm just you or your feet do a different job from those that warm the room. Among room heaters, the air conditioner is cheapest (about 2–4 yen for 6 tatami).
On this page
Cost per hour, ranked
Cheapest first. Gray bars warm the room; yellow bars warm just you or your feet.
Unit price 31 yen/kWh (National Fair Trade Council of Household Electric Appliances guideline, revised July 2022). See the table and "How to read the ranking" for each heater's conditions. 1 tatami ≈ 1.6 m².
The full list, with what each one warms
| Heater | Per hour | Warms |
|---|---|---|
| Wearable blanket | 0 yen | You |
| Electric lap blanket (medium) | ~0.7 yen | Lap, shoulders |
| Electric blanket (medium) | ~0.8 yen | Bed or lap |
| Air conditioner (6 tatami) | ~2–4 yen | Whole room |
| Panel heater 160 W (max) | ~5.0 yen | Around your legs |
| Kotatsu (high) | ~5.3 yen | Feet (shared) |
| Hot carpet 2 tatami (medium) | ~7.1 yen | The floor you sit on |
| Oil heater (6 tatami) | ~10.1 yen | Whole room |
| Ceramic heater (low) | ~18.6 yen | Feet, small spaces |
| Electric stove 900 W | ~27.9 yen | Body in front of it |
| Ceramic heater (high) | ~37.2 yen | Feet, small spaces |
Among room heaters the order is air conditioner < oil heater < ceramic heater. Anything that warms just you or your feet costs less than warming the room.
Combination calculator (per month)
Most people combine heaters over a winter day. Enter the hours and we'll total the cost for a month (30 days).
30 days a month, 3 months (90 days) a winter. Air conditioner: 6 tatami on a cold day (~4.0 yen); oil heater: 8 tatami 18°C average (~14.5 yen); ceramic heater: high (~37.2 yen); kotatsu: high (~5.3 yen); electric blanket: medium (~0.8 yen).
How to read the ranking
-
We compare electricity actually used, not the watts on the box
Electric blankets, kotatsu and oil heaters cut power once warm, so we use energy per hour (Wh) or the average once warm. -
Conditions differ by heater
Electric blanket: Yamazen YFTKB-55 (average over 5 hours in a cotton futon at 15°C). Kotatsu: Yamazen 510 W (maker's figure; test conditions not confirmed). Oil heater: Kakaku.com estimate (De'Longhi, concrete apartment, early-December Tokyo, 9 hours). Air conditioner: the same heat delivered at ~2.5× (cold day) to ~4.7× (7°C) (Daikin S225ATES and others). Ceramic heater: running at high 1,200 W / low 600 W. Electric lap blanket: Koden CWN142H-NC (medium ~23 Wh). It comes from a different maker than the electric blanket (Yamazen), so the gap between 2nd and 3rd is a product difference: Koden's own electric blanket (medium ~18 Wh) is about ¥0.6 an hour. Treat lap blankets and electric blankets as about the same. Panel heater: Iris Ohyama APH-16B at its rated 160 W (maximum). Hot carpet: Panasonic DC-2NK (medium ~230 Wh, 15°C room). Electric stove: running at 900 W (same wattage, same cost whatever the type). -
Your home, region and habits change the numbers
Poor insulation, a colder region or a higher setting push every number up. Use the ranking as a guide to the order, not exact costs.
Which one is right for you?
Answer 6 questions and find the heater that's just right for you.