Heating costs can often be reduced without rebuilding the flat. What matters most is the room temperature, correct ventilation and how the radiators are set. This guide summarises the reference values that the consumer advice service co2online gives, and shows how to put these figures into context for your own flat.
Short answer: The publisher co2online gives around 20 degrees Celsius for living, working and children’s rooms and about 16 degrees for bedrooms and hallways. According to the page, lowering the temperature by one degree can reduce heating energy use by about 6 percent. It recommends short, thorough airing three to four times a day. Last updated: November 2026, figures dated 22 September 2026.
The most important points
- For living, working and children’s rooms, co2online gives about 20 degrees, and for bedrooms and hallways about 16 degrees.
- According to co2online, setting 3 on conventional thermostatic valves corresponds to roughly 20 degrees. Setting 5 does not heat the room faster.
- The page prefers short airing over permanently tilted windows, and the thermostats should be turned down while airing.
- According to the page, one degree less can cut consumption by about 6 percent.
- Whether a measure helps in your flat depends on the building, the heating system and the energy price.
Which room temperature makes sense?
The room temperature is the largest single lever on consumption, because every degree makes a noticeable difference. The consumer advice service co2online gives about 20 degrees Celsius for living, working and children’s rooms. According to the page, about 16 degrees is enough for bedrooms and hallways. If you keep the whole flat evenly at 20 degrees, you heat rooms in which nobody sits for long.
In everyday terms, rooms used only for sleeping do not need a comfort temperature. Closing the door to a seldom used room keeps the heat from spreading unnecessarily into corridors and side rooms.
How do you set the thermostats correctly?
On conventional thermostatic valves, according to co2online, setting 3 corresponds to roughly 20 degrees Celsius. Setting 5 does not bring faster results, only a higher heat input that often goes unused. The page therefore explicitly calls setting 5 no heating turbo. A setting you find once and keep is usually more sensible than frequent turning.
| Room | Reference value from co2online | Note |
|---|---|---|
| Living, working and children’s rooms | about 20 degrees Celsius | Setting 3 on conventional valves |
| Bedroom | about 16 degrees Celsius | A lower value is usually enough |
| Hallway | about 16 degrees Celsius | Little used, so lower |
How do you air correctly without losing heat?
The page recommends short, thorough airing instead of permanently tilted windows. The windows are opened wide for a short time. According to co2online, three to four airing sessions a day make sense. While airing, the thermostatic valves should be turned down so that the heating does not work against the open air.
Permanently tilted windows cool walls and window reveals and still cause a high heat loss. That is one reason why short airing is the better option for many households. It is also important to avoid moisture so that mould does not form.
What does one degree less mean in figures?
According to co2online, lowering the temperature by one degree can reduce heating energy consumption by about 6 percent. The page also gives an example: for a 130 square metre flat with a gas heating system, it states around 1,000 kilowatt hours and about 120 euros in heating costs per year. The publisher stresses that the actual saving depends on the building, the heating system and the energy price.
Assumption: your annual heating costs are 1,200 euros. A reduction of one degree would then amount, on paper, to 6 percent of that, or 72 euros. The figure is only a guide. How much of it actually shows in your statement becomes clear only from consumption over a full year.
Which measures work without renovation?
Many measures cost nothing or little. These include keeping radiators free of furniture and curtains, closing shutters at night and checking window seals. A window door with draughts is also worth a look. Concrete savings figures for these measures are not documented in the sources reviewed, so this guide gives no numbers for them.
Why furniture in front of radiators slows the warmth
A radiator hidden behind a sofa, a curtain or a cabinet releases its heat only partly into the room. The air circulates less well, and the room still does not warm up, because the heating has to run longer. Clear space in front of the radiator is therefore one of the simplest measures, and it costs nothing.
The same applies to radiator covers and blinds directly above a radiator. If you have a cover, check whether it traps the heat rather than distributing it.
How to track consumption over the year
A one-off change only helps if you check it over the winter. Note the meter reading or your monthly consumption figure at the start of each month. That way you can see whether consumption changes when you adjust temperatures or airing habits. Compare periods that were similarly cold, because a mild January can change the figures more than any measure.
Frequently asked questions about heating in a rented flat
May I set the heating in a rented flat myself?
Yes, the thermostats are part of operating the flat. Whether minimum temperatures are set in the tenancy agreement or house rules should still be checked. If there is a risk of mould from low temperatures, inform the landlord.
Is airing in winter worthwhile at all?
Yes. Airing is particularly important in winter to remove moisture. Short airing following co2online’s recommendations combines a good exchange of air with a low heat loss, because the windows are open only briefly.
Why are heating costs sometimes higher despite saving?
Heating costs also depend on weather, building and energy prices. A colder winter or rising prices can outweigh a lower room temperature. It therefore makes sense to compare consumption over several years, not just one month.
What you should do now
- Read your latest heating cost statement and note consumption and costs per year.
- Set the thermostats for each room to a fixed value and record the setting.
- Adopt short airing, three to four brief sessions a day, and turn the thermostats down during it.
- After a winter, compare consumption with the previous year and check the statement for irregularities.
Related guides
- Climate, energy and living costs 2027: the overview for tenants and students (hub for this topic)
- Checking the heating cost statement: deadlines, distribution and typical errors
- CO2 price 2027: what the price corridor means for heating and fuel
- Saving electricity as a student: energy and utility costs (in German)
Sources: co2online, guide on heating and ventilation, article dated 22 September 2026 (publisher co2online).
Last updated: November 2026. This guide is general information, not individual advice.
