Which radiator power to choose per m²?

The criteria for determining the necessary power

To give an initial orientation, an estimate of the average heating power has been calculated on the basis of a dwelling with a standard ceiling height of 2.5 meters : she is at between 70 and 100 watts per square meter. For the choice of the power of your radiators, you can actually use this indication, but for optimal comfort and lower consumption, it is better to refine this estimate according to different criteria.

The heating power per cubic meter

First of all, it is necessary to lean on the volume of each part to be heatedr. This will give you an indication of the heating power needed in each, because the volume of each room is equivalent to the volume of air that will be heated, regardless of your type of heating, heat pump, boiler, etc.

You should know that in general, a power of 750 kWh can heat an area of ​​approximately 25m3 if your room has a standard ceiling height of 2.5 m.

To do this, nothing could be simpler, just multiply the length of the room by its width and height.

Or the formula:

Once you know the volume of the room, this allows you to have one of the first elements necessary to evaluate the heating power required. But this is not enough, because the insulation and the geographical location of your accommodation will also come to bring their grain of salt.

thermal insulation

As we have seen, thermal insulation is a factor to consider to determine the heating power required in the rooms of a dwelling. And for good reason, a house that will be poorly insulated will need more heatsink power to make up for losses and heat the room sufficiently, this corresponds to the heat loss coefficient of a dwelling.

Depending on the level of insulation in your home, this coefficient goes from 0 to 3. The number 0 corresponds to the most energy-consuming dwellings and the number 3 to the least energy-consuming. For this reason, when one wishes to improve thermal comfort and save money, it is necessary to start by carrying out a heat balance to determine and eliminate areas of heat loss.

The geographical location of your accommodation

The geographical location of your home is another criterion that you must take into account when choosing the power of your installations. Depending on the geographical data of your home, such as altitude, whether it is a humid area or not, the exposure of your home, the general climate, etc., the heating power for the same volume will not be the same.

To take this criterion into account, heating engineers calculate the difference between the lowest temperature in your area (base temperature) and the temperature you want to have in your home (reference temperature). The result obtained is called “delta”.

Average radiator powers

To help you, we suggest you discover the average power of radiators according to your geographical location and the insulation of your home.

How to calculate the required power accurately?

Now that we have seen the different criteria to take into account, you will be able to calculate more precisely the power needed to allow your heating to perform efficiently and provide you with quality thermal comfort.

Here is the formula to apply:

• P = V x G x ΔT
  • G is equivalent to the volume loss coefficient. As we have seen, this coefficient is determined by the insulation of your home and ranges from 0 to 3.
  • ΔT, which corresponds to the delta we talked about a little earlier, obtained by taking the difference between the desired temperature and the minimum temperature of your region.
  • As for V, it is the volume of the parts to be heated.

Once this calculation is done, you obtain P which corresponds to the power in watts necessary for your heating, but do not forget that you must take into account the possible losses. To do this, multiply P first by 1.1, then by 1.2. In other words, you will perform the following calculation:

There you have it, you have the power you need for your installation. Thanks to that, you will avoid overconsumption and, as a result, higher energy bills. But you have probably seen it, all this is very complicated! It is still preferable to call on a professional who can best estimate the power required and you will be sure that your heating system will be perfectly sized in relation to all the criteria and your needs.

Do you need one or more radiators to heat a room?

Once the power of your radiator has been determined, it is necessary to choose its location, but also to determine the number of devices to be installed. This criterion varies depending on the size of the room. For instance :

• When you want to heat a room measuring more than 30 m², it is necessary to install two radiators. Their location must be strategic to allow the most homogeneous heat radiation possible. The larger the room, the greater the number of radiators.
• For a room measuring between 10 to 15 m², a single radiator is sufficient. It is therefore preferable to avoid installing it near the bed.

You should know that inertia radiators diffuse the heat stored for a longer time, so this is the type of model to choose when choosing.

Heat to the right temperature

Once your radiators are installed, you can finally heat your room, but don’t forget that in France, heating expenses constitute an important part of household budgets: they represent 60-75% of total energy consumption. So, to limit costs, but also reduce your impact on the environment, be sure to heat each room to the right temperature. ADEME estimates thatby lowering the heater by 1°C, you can save up to 7% on your energy bill.

Here is what is recommended:

• 19°C for living rooms, such as the living room, dining room, kitchen;
• 17°C in the bedrooms and passage rooms, such as the hallway, the entrance, the toilets and the bathroom. You can raise the temperature of the latter when using it.

To simplify the various settings and change the temperature according to your needs, it is possible to opt for connected models that you can control remotely. So if you’re away for several days, you can lower the temperature to 14°C and raise it remotely before you return.