Ideal Heating Temperature, Room by Room

19 to 20 °C in living areas, 16 to 17 °C in an adult bedroom, 22 °C in the bathroom while the shower is running and not otherwise. That is the short answer, and it is broadly the same across northern Europe. The interesting part starts afterwards, when you put a price on each of those degrees and work out where the famous 7 % figure actually comes from.

What is the ideal temperature in a home?

19 °C in occupied rooms is the benchmark Belgian bodies settle on.

Homegrade, the Brussels public housing information service, makes a point most guides skip: this is not a setpoint to apply room by room, it is an average for the whole dwelling. Heating a hallway and a living room to the same temperature makes no thermal sense, and it costs money.

Perceived comfort does not depend on the thermometer alone. A poorly insulated wall at 15 °C radiates cold: in a room at 20 °C with cold walls you will feel as though you are in a room at 18 °C, and you will raise the setpoint to compensate for insulation rather than for temperature.

What temperature for each room?

The table below lists the ranges used by Belgian regional bodies and heating engineers. These are ranges, not standards.

A bathroom held at 22 °C all day for twenty minutes of showering is the most common and most pointless expense in Belgian homes. A programmable thermostat, or simply a thermostatic radiator valve set to peak use, solves it.

Why does one degree less save 7 %?

Because 1 divided by 13.7 gives 7.3 %. The figure is not an observation, it is a division.

A building's heating demand is proportional to the gap between the indoor and the outdoor temperature. That basic physical law is enough to explain everything. The RMI publishes 15/15 degree days for Uccle, the Belgian reference indicator that accumulates the daily gap between 15 °C and the mean temperature of the day. The RMI, or Royal Meteorological Institute, is Belgium's national weather service. The annual normal sits around 2,000 degree days, spread over a heating season of roughly 230 days.

Divide: 2,000 ÷ 230 gives about 8.7 K of average gap below the 15 °C threshold. The average outdoor temperature during the Belgian heating season therefore sits around 6.3 °C.

The rest is trivial. With a 20 °C setpoint, the average gap to bridge is 20 minus 6.3, or 13.7 K. At 19 °C it falls to 12.7 K. The ratio gives 12.7 ÷ 13.7 = 92.7 %, meaning 7.3 % less heating demand. The 7 % figure that every article has been repeating for fifteen years has no other origin than this division, which is also why it holds for neither Madrid nor Helsinki.

Two consequences that the usual shortcuts flatten. First: those 7 % apply to space heating alone. Your hot water tank and your hob will not consume a single kilowatt-hour less because you touched the thermostat. Second, and this one often surprises: in percentage terms the saving is identical in a passive house and in a thermal sieve, since the ratio 12.7 ÷ 13.7 does not depend on heat losses. In euros, everything changes.

The percentage is the same for everyone. The bill depends entirely on the quality of the building fabric.

What does one extra degree cost at Belgian gas prices?

Between 58 and 135 € a year depending on the home, based on our own calculation assumptions.

Three inputs go into the calculation, and we set them out explicitly so you can redo it with your own. The gas price used is 0.11 €/kWh all in, an order of magnitude for the Belgian residential market recorded in late August 2026 in our tracking of the price of gas in Belgium, taxes, distribution and VAT included. Space heating is estimated at 80 % of gas consumption in a home that also produces its hot water with gas. The sensitivity per degree is the one demonstrated above, 7.3 %.

The starting consumption figures come from our published ranges on average gas consumption in Belgium.

The D3a profile is the standard household consumption profile defined by the CREG, the federal energy regulator, and it is the yardstick most Belgian price comparisons use.

Two degrees of excess setpoint in a detached house cost 270 € a year. The same mistake in a flat costs 116. That gap explains why universal thermostat advice leaves so many people sceptical: it is right in percentage terms and wrong in euros.

What temperature should a bedroom be at night?

16 to 17 °C for an adult, 18 to 19 °C for an infant.

Deep sleep goes with a drop in body temperature, which an overheated bedroom works against. Above 19 °C sleep quality deteriorates for most sleepers, which makes the bedroom the one place in the home where saving money and comfort pull in the same direction.

Going down to 14 °C poses no danger to a healthy, properly covered adult. The real risk lies elsewhere. In a damp home, a wall surface falling below the dew point produces condensation, then mould behind furniture and in corners. A cold, ventilated bedroom stays healthy; a cold, sealed one does not.

Never shut a radiator off completely in an unoccupied bedroom during winter: leave it on frost protection. An unheated room draws heat from adjoining rooms through the partition walls, and moisture builds up in it.

Should you switch the heating off when you go away?

Turn it down, yes. Switch it off, almost never.

For an absence of a few hours to a day, a setback to 16 °C returns 10 to 15 % over the period, according to the benchmarks published by Belgian regional services. For a long absence, frost protection at around 7 °C is the right position.

Between the two, the answer depends on the building's thermal inertia. An old house with thick walls takes a very long time to cool down and just as long to recover: short setbacks achieve almost nothing there. A lightweight, well-insulated build reacts quickly and lends itself far better to time programming.

The received wisdom that restarting the heating costs more than keeping it on is false. A home that has cooled down consumed less during the setback, in exactly the proportion of the temperature gap avoided.

Six adjustments that matter more than one degree of setpoint

• The boiler's heating curve, set once by a heating engineer, works all season without you touching anything. It is the only item on this list that takes ten minutes and pays back for ten years.
• Bleeding the radiators at the start of the season. A radiator that is cold at the top heats through a fraction of its surface while the boiler runs as though it were full.
• Balancing the system, when some rooms overheat while others stay cold. That imbalance is almost always what pushes people to raise the general setpoint.
• Thermostatic radiator valves, which are what let you actually apply the room-by-room table above. Without them, the single thermostat setpoint rules everywhere.
• Time programming, which pays better than a permanent one-degree setback in a home left empty during the day.
• The curtain or the piece of furniture in front of a radiator, which blocks convection and costs several percent of emission efficiency without any device flagging it.

What temperature should the hot water tank be set to?

60 °C, and that is not negotiable downwards for the sake of savings.

Legionella multiplies in lukewarm water, roughly between 25 and 45 °C. It is destroyed in about thirty minutes at 60 °C and almost instantly at 70 °C. The Belgian technical standards for domestic hot water specify 60 °C in storage and a minimum of 55 °C in the distribution network.

Setting a tank to 50 °C to gain a few euros a year is therefore a bad trade. The correct compromise exists and is called a thermostatic mixing valve: the tank stores at 60 °C for sanitary safety, the valve delivers 38 °C at the tap to prevent scalding.

The boiler flow temperature matters more than the setpoint

A thermostat states the temperature you want to live at. The heating curve states the temperature at which the boiler sends its water out. The second one decides efficiency, and almost nobody looks at it.

A condensing gas boiler only condenses, and therefore only delivers its stated efficiency, if the water returning to it falls below the dew point of the flue gases, around 55 °C. Set to an 80 °C flow, it behaves like a conventional boiler and permanently loses several efficiency points, winter after winter, with no visible signal on the appliance. Manufacturer documentation is explicit on this, and Bulex, a manufacturer active on the Belgian market, documents the relationship between room temperature and control in its consumer material.

The order of magnitude deserves stating: a few efficiency points lost on 13,600 kWh of annual heating amount to more than the degree of setpoint you are working so hard to save. The heating curve is adjusted during servicing, by an approved professional. Ask for it explicitly, because it is not automatic.

Wallonia, Brussels, Flanders: three frameworks for the same degree

The physics is identical in all three regions. The regulatory framework and the bill are not.

The servicing intervals come from each region's heating regulations, and the certificate issued by the technician is the proof. Failing to comply exposes you to more than a fine: an insurer can refuse to pay out after an incident linked to an unserviced installation. The 2026 distribution increases are those we recorded in our July and August 2026 tariff tracking, from publications by the CWaPE, the Walloon energy regulator, and from the grids of the DSOs, the distribution system operators that own the network and that you do not get to choose. The Flemish capacity tariff, which bills the quarter-hourly power peak, applies to electricity only and leaves gas untouched.

In Wallonia, the combination of a 14 % distribution increase and a three-yearly servicing requirement produces a perverse effect that is rarely mentioned: the degree costs more than elsewhere, and the installation is checked less often. It is the region where deliberate adjustment counts for most.

Where to go next

Settings determine the number of kilowatt-hours. The contract determines their price, and the two levers stack. Once your setpoints are dialled in, take your annual consumption to the energy supplier ranking, which reasons in total annual cost rather than in headline price per kWh. If your bill is expressed in cubic metres rather than kilowatt-hours, our method for converting gas m³ into kWh gives you the conversion basis to use in the tables above.

Sources: RMI, 15/15 degree days for Uccle, 1991-2020 normals, heating season and the 15 °C threshold (accessed 31 August 2026); Homegrade Brussels, domestic heating management, the 19 °C benchmark and the whole-dwelling average principle (accessed 31 August 2026); Energie Plus, standards for domestic hot water, 60 °C in storage and 55 °C in distribution, legionella growth range (accessed 31 August 2026); Bulex, consumer documentation on room temperature and control (accessed 31 August 2026); gas boiler servicing intervals from the Walloon, Brussels and Flemish regional heating regulations in force in 2026. Gas price: 0.11 €/kWh all in, an order of magnitude for the Belgian residential market recorded in late August 2026, to be rechecked before any decision since variable contracts are reindexed every month. The cost of one degree, the 80 % share attributed to space heating and the 7.3 % sensitivity per degree are our own assumptions, set out in the article so anyone can redo them with their own figures.