The radiator dial has five numbers and a snowflake, but no one ever included an instruction manual. That’s the source of most household heating misunderstandings: someone turns it all the way up to heat the room faster, someone else turns everything down to zero before leaving for work, and the bill still comes in higher than it should. W this article, we explain what the numbers mean, what temperature works best in each room, and how much you can actually save by turning it down by one degree.
What the numbers on a thermostatic radiator valve mean
The most important thing to know to start with: the number on the dial isn’t the heating power, but the temperature you want in the room. Inside, the valve has a sensor that measures the air around it and opens or partially closes the hot water supply to the radiator. You set a target, not the heat level.
The settings correspond roughly to the following temperatures:
| Setting | Temperature | Where it’s suitable |
|---|---|---|
| ❄ | approx. 6 to 8°C | protection against the system freezing only |
| 1 | approx. 12 to 14°C | vestibule, garage, utility rooms |
| 2 | approx. 15 to 16°C | bedroom |
| 3 | approx. 20 to 22°C | living room, lounge, study |
| 4 | approx. 22 to 24°C | bathroom |
| 5 | approx. 26 to 28°C | maximum setting, not needed day to day |
The ranges vary slightly depending on the valve manufacturer, so treat them as a guide rather than exact values. The principle is the same for all of them, though: the higher the number, the warmer the room will be before the radiator stops heating.
Why the setting doesn’t affect how quickly a room warms up
This is probably the most common misconception about heating. When you return to a cold apartment, your instinct tells you to turn the dial all the way up to speed up the heating process. But a thermostatic radiator valve doesn’t work like a gas pedal.
If the room is cooler than the set temperature, the valve opens all the way, whether it’s set to three or five. Exactly the same amount of hot water flows to the radiator. The difference only appears at the end: at three, the radiator will shut off when the room reaches 20 to 22 degrees, while at five it will keep heating until it reaches 26 or 28. The room will warm up just as quickly; it’s just that in the second case, it won’t stop when the room becomes comfortable.
So you end up paying to overheat the room, not to heat it faster. If you want it to warm up faster, uncovering the radiator and closing the room door works better than changing the settings.
What temperature should each room be?
Setting the same temperature everywhere is convenient, but costly. The biggest savings come from adjusting temperatures for different rooms: you simply don’t need as many degrees in the kitchen and bedroom as in the living room.
A good starting point is the guidance from the World Health Organization (Housing and Health Guidelines). WHO recommends 18°C as the minimum safe temperature for healthy adults during the heating season. Below this threshold, the risk of health problems increases, especially for children and older people, so this isn’t where you should try to save money at all costs.
- Living room and family room: 20 to 22°C. You spend the most time sitting still here, so you feel the cold most.
- Bedroom: 15 to 18°C. Cooler air helps you sleep better, and it’s warm under the covers anyway.
- Bathroom: 22 to 24°C. It’s the only room where you’re likely to be wet and undressed, so a higher temperature makes sense here.
- Kitchen: 18 to 20°C. The oven, stovetop, and refrigerator all give off quite a bit of heat on their own.
- Rooms that are rarely used: at least 15°C. No lower, because cold walls start to collect moisture.
Turning the heating down at night and when you’re away
Turning off all the radiators before leaving for work seems like the easiest way to save money. W practice, it usually doesn’t pay off, and it’s worth knowing why.
Heat isn’t just in the air. It’s stored in the walls, floors, furniture, and the building as a whole. Going without heating for a few hours cools not only the air, which warms up quickly, but also all those surfaces, which take a long time and a lot of energy to warm up. When you get back, the heating system has to make up for all that heat loss, using more energy than it would have taken to maintain a slightly lower temperature during that time.
That’s why it’s more sensible to turn it down by 2 to 3 degrees, for example, turning the dial from three to two, rather than turning it all the way off. The house won’t have time to get cold, and you won’t pay extra to warm up the walls again.
How much you’ll save by turning the heating down by one degree
W the energy sector, there is a simple rule of thumb: each degree lower means about 5 to 8 percent less heat energy used, or around 6 percent on average. The same figure is independently cited by the German Energy Agency, dena, and the Polish heating industry’s “20 Degrees for the Climate” campaign, run by the Chamber of Commerce Polish District Heating.
Where does this figure come from? A radiator gives off heat to make up for the difference between the temperature in the room and the temperature outside. W the heating season, this difference averages around a dozen degrees. So one degree is roughly one-twelfth of all the work the heating system has to do, which is where those few percent come from.
Important caveat: this is a rule of thumb, not a fixed physical constant that applies equally to every home. W a poorly insulated building, the reduction in kilowatt-hours used will be significantly greater because heat loss is higher. W a well-insulated home, where the sun and the occupants’ daily activities provide a lot of heat, that same one-degree reduction will make a proportionally smaller difference.
Why the dial in an apartment building won’t go below two
If you live in an apartment building and the thermostatic radiator valve has a limiter that prevents you from turning it down further, that is not a fault or a malicious act by the building management. It is the result of a requirement set out in the Regulation of the Minister of Infrastructure on the technical conditions to be met by buildings and their location.
It is worth clarifying right away who this regulation applies to, as it is often a source of misunderstanding. Section 134 specifies the properties required of the installation: in buildings supplied by a district heating network or by their own source of oil, gas or electricity, the controls must operate automatically and allow the temperature to be lowered, but not below 16°C in rooms with a design temperature of 20 degrees or higher. This is a technical requirement for the equipment and the installation design, not a ban directed at tenants or a rule specifying how many degrees you are allowed to have in your living room.
Where did this particular limit come from in the first place? Mainly out of concern for the building itself. Walls that get very cold, especially in corners, around windows and behind furniture, start to collect condensation, which can quickly lead to damp and mold. In a living room that rarely falls below this value, this is more of a theoretical concern, but in a north-facing room that is used less often, it is very much a practical one. A secondary reason is that a cold apartment draws some heat through the walls from neighboring apartments.
There’s also a purely financial point worth knowing when planning how to save money in an apartment building. With billing based on heat cost allocators, the rules usually provide for a minimum variable charge and adjustment factors for apartments in less favorable locations. W practice, this means that turning the temperature way down doesn’t always reduce your bill in the same proportion you might expect from the allocator readings. You can find the rules in your housing cooperative’s or association’s billing policy.
One important caveat: the same rule does not apply to single-family homes, farmstead buildings, individual recreational buildings, or apartments with their own heating system. If you live in a house or have your own boiler in your apartment, you can set the valves however you like, including to the snowflake setting.
Common mistakes
- Radiator blocked by furniture or covered by a curtain. This causes two problems. Heat doesn’t circulate around the room as well, and the sensor in the valve measures the air trapped behind the obstruction, which is warmer than the rest of the room. The valve therefore assumes the room is already warm and closes, even though the room is still cool.
- Dusty radiator fins. A layer of dust between the fins acts like a blanket and noticeably reduces heat output. Vacuuming the radiator before the heating season takes just a few minutes and can make a difference to your heating costs.
- Thermostatic radiator valve facing the wrong way. The sensor should be exposed to the air in the room. If the valve is turned toward the wall or points down toward the pipes and radiator, it measures their heat instead of the room temperature and switches off the heating too soon. A correctly installed valve is positioned horizontally and faces into the room.
- Ventilating with the radiator turned up. The influx of cold air makes the valve open fully, so the radiator works as hard as it can to heat air that will soon escape through the window. The correct order is: turn the valve down to its lowest setting, ventilate intensively for 5 to 10 minutes, close the window, then turn the valve back up.
What to do if adjustment alone isn’t enough
Adjusting thermostatic radiator valves is the first and simplest step, but it’s not the only option available to you. Sometimes, even with the settings adjusted correctly, some rooms heat up much less than others. In that case, the problem isn’t the valves themselves, but how water is distributed among the individual radiators throughout the system, a process known as hydraulic balancing.
A separate, independent control is the boiler water outlet temperature, set on the boiler itself or its controller, as well as the circulation pump setting, which determines how much water circulates through the system. These are three different levels of control, and only together do they give you the full picture of heating costs.
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Frequently asked questions
What do the numbers on a thermostatic radiator valve mean?
The numbers correspond to the target room temperature, not the heating intensity. As a guide: 1 is around 12 to 14°C, 2 is 15 to 16°C, 3 is 20 to 22°C, 4 is 22 to 24°C, and 5 is 26 to 28°C. Exact values vary slightly between thermostatic valve manufacturers.
Does setting the thermostatic valve to maximum make the room heat up faster?
No. The radiator valve opens fully regardless of the number selected when the room is cooler than the set temperature. A higher number simply means a higher threshold at which the valve closes, resulting in greater energy consumption, not faster comfort.
How much do I save by lowering the heating by 1 degree?
About 5 to 8%, with an average reduction of 6% in heating energy consumption for each degree lowered. The German Energy Agency dena and the Polish district heating industry campaign “20 degrees for the climate” cite the same figure. W a poorly insulated home, the effect will be greater; in a well-insulated one, smaller.
Why won’t the thermostatic valve in my apartment go below setting 2?
This follows from Section 134 of the Regulation of the Minister of Infrastructure on the technical requirements for buildings. The regulation states that in multi-unit buildings supplied by a district heating network or their own source of oil, gas or electricity, the controls must allow the temperature to be lowered, but not below 16°C. This is a technical requirement for the heating system, not a restriction imposed on residents. It does not apply to single-family homes or apartments with their own heating system.
Why does a radiator heat less when it’s blocked by furniture?
The sensor in the thermostatic radiator valve detects the temperature of the air trapped right next to the radiator. If that air is warmer than the rest of the room because a piece of furniture or a curtain is blocking the radiator, the valve closes prematurely, before the whole room has had a chance to warm up.
Is it worth turning off the heating completely when you’re away from home?
Usually not. Walls and floors store heat, so cooling them completely takes more energy to warm them up again than maintaining a steady, slightly lower temperature for the same amount of time. It’s safer to lower the temperature by 2 to 3°C rather than turn the radiator all the way down to zero.
