Ondol floor heating and winter gas bills in Korea: boiler settings and tips

TUREFF• •0

Your first Korean winter comes with two surprises: a warm floor that feels like a luxury, and a gas bill that can be bigger than you expected. Most homes in Korea are heated by ondol, underfloor heating fed by a gas boiler. Here is how it works and how to keep it comfortable without overspending.

How ondol works

Traditional ondol carried smoke from a kitchen fire under stone floors. Modern homes use the same idea with hot water: a gas boiler heats water and pumps it through pipes in the floor. The floor warms slowly and then holds the heat, which is why Koreans sit, eat and even sleep on the floor in winter. Because the floor is the heater, it takes time to warm up. Turning it off completely during the day and blasting it at night is usually less efficient than keeping it steady.

Your boiler controller

The control panel is usually on the wall in the living room or kitchen. Labels are in Korean, so learn these:

난방 (nanbang): heating on.
온수 (onsu): hot water only, no heating. Use in warmer months.
외출 (oechul): "going out" mode. It keeps the system at a low level so the pipes do not freeze and the floor does not go completely cold. Use it when you leave for the day.
예약 (yeyak): timer or reservation mode. Typically the boiler runs for a set period at regular intervals (for example, every few hours). Many people find this the cheapest way to keep a flat warm.
실내온도 / 온돌 (silnae ondo / ondol): heating by room temperature or by floor water temperature, depending on the model.
Arrows (▲▼): set the target temperature.

Boiler models differ, so search the brand and model number (written on the panel or the boiler itself) for an English manual, or ask your landlord to show you.

What drives the bill

The size and age of the flat: older buildings and top or corner flats lose more heat.
Windows: single glazing or gaps around the frames leak a lot.
How warm you keep it: every degree counts.
The season: gas prices are set by city gas suppliers and the government, and bills peak in January and February.

Bills come monthly from the local city gas company, often through an app or the building management fee. You may need to report the meter reading yourself in some areas.

Keeping costs down

Keep a steady, modest temperature rather than switching between off and very hot.
Use 외출 or 예약 when you are out instead of turning it off.
Close off rooms you do not use: many flats have a valve for each room's floor loop near the boiler or under the sink manifold.
Insulate windows: bubble wrap film (뽁뽁이) for glass and draught strips for frames are sold cheaply at Daiso and supermarkets.
Rugs and thick curtains keep heat in.
Dress for it: indoor slippers, warm layers and an electric blanket (전기장판) for the bed. Electric blankets are very popular because they warm you instead of the whole room.
Check for discounts: some cities and gas companies offer savings programmes for reduced usage; look at your supplier's website.

Condensation and mould

Warm floors, cold windows and drying laundry indoors make Korean flats prone to condensation and black mould, especially in corners and behind furniture.

Air the flat for a few minutes once or twice a day, even when it is cold.
Use the kitchen and bathroom fans.
Wipe condensation off windows in the morning.
Leave a gap between furniture and outside walls.
A dehumidifier helps if you dry clothes inside.

Preventing frozen pipes

Cold snaps in Korea can be fierce, and frozen pipes and boilers are common problems in older buildings.

Never turn the boiler fully off during a hard freeze; use 외출 mode.
If you go away, leave the boiler on low and ask your landlord about anything else needed.
On the coldest nights, leave a tap running slightly so water keeps moving.
Wrap exposed pipes and the water meter box (on a balcony or corridor) with insulation or old towels.
Keep the balcony door or window by the boiler closed.

If the boiler stops, the display usually shows an error code. Call the number on the boiler or tell your landlord; repairs to the building's equipment are generally the landlord's job. How do you deal with Korean winter heating, and what did your first gas bill look like? Share your tips or ask questions in the comments.