A kotatsu is a low wooden table with an electric heating element attached to the underside of the tabletop. A thick quilted blanket (kotatsu-buton) is sandwiched between the tabletop and the frame, draped down to the floor on all sides. People sit on cushions on the floor and slide their legs into the warm space underneath. The modern electric version evolved from older charcoal-pit kotatsu that go back several centuries; the electric kotatsu became a household standard from the 1950s onward.

How much electricity does a kotatsu use?

A modern kotatsu typically draws between 80 and 200 watts on its lowest setting and 300–600 watts at high. In real-world Japanese household use, that works out to roughly 2–5 yen per hour at standard residential electricity rates, far less than a typical air conditioner used for heating. This is one of the main reasons the kotatsu remains popular: it warms only the small enclosed volume around your legs, not the whole room.

Why don't Japanese homes have central heating?

Most Japanese homes — outside Hokkaido — were historically built with low insulation and an emphasis on summer ventilation, since hot humid summers were the more dangerous half of the year. Whole-house central heating never became standard. Instead, Japanese winters are managed with localized heat: a kotatsu in the living room, an electric carpet (hot-carpet), reverse-cycle air conditioners, a kerosene stove, and heated toilet seats. The kotatsu is the social center of that system.

Today I Learned

Japan, apparently, still heats half of its households by sticking everyone's legs under the same blanketed table

The kotatsu — a low table with a heater underneath and a heavy quilt across the top — is used in roughly half of Japanese homes each winter, and costs only a few yen per hour to run.

Published 2026-05-01 · 2 min read · By Daichi

◇ A low wooden table covered with a thick quilted blanket, a tatami floor underneath, with two pairs of socked feet visible at the edges and a teapot and mikan oranges on the tabletop

It is mid-January in a Japanese house. The hallway is cold, the bathroom is cold, and the bedroom is cold. The living room is also cold — except for one specific volume of air, about the size of a coffee table, where the temperature is roughly 35 °C and rising. Four people are sitting on the floor around the table, blanket pulled up to their waists, peeling mikan oranges, watching a variety show, and refusing to move. Someone falls asleep with their head on the tabletop. This is normal. This is, in fact, the point.

The kotatsu is the most efficient piece of furniture in Japan, and for a substantial fraction of the population, it is also the entire winter.

The fact

A kotatsu is a low wooden table with an electric heating element fixed to the underside of the tabletop. A heavy quilted blanket — the kotatsu-buton — is sandwiched between the table frame and a removable upper tabletop, draped down to cover the legs of anyone sitting around it. People sit on floor cushions, slide their legs into the enclosed cavity, and the trapped warm air pools around them.

Surveys by Japan’s Ministry of Internal Affairs and Communications have reported that roughly half of Japanese households own a kotatsu — that share is higher in the snow country and Kansai, lower in Hokkaido (where homes are better insulated and have central heating) and in compact Tokyo apartments.

Power consumption is the genuinely surprising number. A modern kotatsu typically runs between 80 and 200 watts on low and 300–600 watts on high, working out to roughly ¥2–5 per hour in real use — a small fraction of the cost of running an air conditioner for room heating, because you are heating a volume the size of a suitcase rather than a room.

Why it works this way

Three forces stack:

Japanese houses are not insulated. Most homes outside Hokkaido were historically built for summer — high ventilation, low thermal mass, single-glazed windows. Heating the whole house is expensive and slow. Heating one cubic meter of air around your legs is cheap and instant.
Floor seating is the architectural baseline. Tatami rooms, the zashiki style, and the long tradition of sitting seiza on the floor turn the floor into the family’s daily plane. A heated table at floor level is a more natural extension of that than a Western armchair-and-radiator setup.
It is a social trap, by design. Once everyone’s legs are inside the same warm pocket, leaving requires a deliberate act of cold-air exposure. The result is an extended family sitting together for hours over tea and oranges. Magazines and TV affectionately call this kotatsu kara derarenai — “I can’t get out of the kotatsu.”

The kotatsu has been declared dead at least once a decade since the 1990s, as apartments shrink and air conditioners improve. It keeps not dying. New compact and one-touch kotatsu models still sell into the millions of units annually.

Where to experience it

A traditional ryokan (inn) in winter — almost any ryokan in Hakone, Kusatsu, Nikko, or Kinosaki will have a kotatsu in the room. Many traditional inns serve dinner directly on the kotatsu tabletop.
A countryside guesthouse in the snow country — Niigata, Tohoku, and inland Nagano are the cultural heartland of the kotatsu. Family-run inns there often build evenings around it.
Cat cafés and “kotatsu cafés” in Tokyo and Kyoto — seasonal kotatsu setups appear in winter, often paired with hot tea, mikan oranges, and a sleeping cat that defends the heat source.

Closing

A whole-house furnace heats the rooms you do not use. A kotatsu heats the people you actually live with. Apparently, with one heating element and one big blanket, half of Japan has solved a problem the rest of the rich world solves with central heating — and gotten a family ritual out of it.

The most efficient social object in Japan

The fact

Why it works this way

Where to experience it

Closing