Calculate radiator power

With the cold weather comes the season to turn on the heating and depending on the type of housing, we may have to resort to electric radiators to heat our house and rooms. To help you choose the radiator power you need, below you will find a calculator that will give you the result based on the type of insulation of the house, the square meters, the climate and the room.

Keep in mind that the radiator power value shown by the calculator will be the minimum you need to avoid getting cold.

Recommended temperatures for your home

Many people in winter abuse the temperature and this causes an exponential increase in the cost of the electricity bill if we have electric radiators, stoves, thermal emitters or any other type of heating powered by electricity.

Here are some temperature recommendations that you should follow to avoid skyrocketing electricity bills during the day:

  • Living room comfort temperature: 21ºC or 22ºC maximum.
  • Bedrooms: 20ºC
  • Comfort temperature in corridors and common areas: 18ºC 0 19ºC.

When night comes we can turn off the heating if the climate of the city where we live is not very cold and the insulation of the house is good. Otherwise, it is advisable to adjust the heating temperature to the following values:

  • Bedrooms (while we sleep): 17ºC
  • Living room: 18ºC
  • Corridors and common areas: 18ºC

Following these steps will prevent the house from getting cold during the night and during the day we will have to use much more energy to heat it.

How to calculate the power of electric radiators

When calculating the power required to use electric radiators, we must take into account a number of factors that will make us need more or less power. Below we will see what they are:

Square meters

The larger the surface area of the room, the greater the power to heat the volume of cold air in the room.

Type of climate

Type of weather in winter

Depending on the area where we live, the winter will be more or less hard. The winter in Reinosa is not the same as in Malaga, so you will have to take this into account. Here are the values that we will use later in the formula to calculate the power of the radiators:

  • Extreme Cold: 20
  • Very cold: 16
  • Cold: 15
  • Soft: 13

If you do not know what type of climate the area where you live has, the map above these lines can help you to find out.


As we have seen before, depending on the type of room we will need more or less temperature. It is normal to heat at 20ºC rooms where we spend more time, such as the living room or bedrooms.

On the other hand, it is not necessary to heat the passage areas such as the hall or corridors as much, although it is not advisable to have a big difference in temperature with respect to the rooms or every time we move from one room to another we will notice a big contrast in temperature. The ideal is to put them to 19ºC

Here are the values we will use in the formula depending on the room:

  • Living room, bathroom: 1.1
  • Bedroom: 1
  • Kitchen, lobby or corridors: 0.9


Good insulation is essential for heating a house in winter. If we have leaks in windows and doors, part of the heat emitted by the heating system will be lost and we will need much more energy to heat the house.

These are the values to be used in the formula depending on the type of insulation of the area to be heated:

  • Without insulation: 12
  • Regular: 14
  • Good insulation: 12

Formula for calculating the power of electric radiators

Now yes, the formula for calculating the power of electric radiators is:

W = ((Insulation + Type of climate) x Stay x m2 x 250)/ 86

For example, let's imagine that we live in Valladolid and we want to heat a 10-meter room.2 which is well insulated. The formula will look like this:

W = ((12 +16) x 1 x 10m2 x 250)/ 86 = 814W

That is, we will need a radiator or thermal emitter of at least that power. If you buy 800W, you may heat the room but you will never reach the desired temperature because the power would be below.

If you buy it from 900W upwards, you will heat the room earlier and it will also reach the desired temperature, so the thermostat of the radiator will automatically turn it off and you will end up consuming less electricity by not having to be constantly running at maximum.

Below you have some tables with the W/m2 coefficient already calculated so that you only have to multiply its value by the square meters of the room to heat.

Housing with thermal insulation:

Housing with Thermal Insulation

Housing without adequate thermal insulation:

Housing without thermal insulation

Types of electric heating

In today's market there is a wide variety of products to heat the house using electricity. Below we are going to tell you what they are and the pros and cons of each one:

Thermal emitters

Thermal emitter

Thermal emitters are aluminum radiators that have a heating element that heats up and emits a large amount of heat almost immediately, so if we have one of the correct power, it will heat a room in a short time.

Consumen "poco" y su precio es medio ya que no es la opción más barata pero tampoco la más cara. Aunque cuesten un poco más, lo ahorraremos en poco tiempo en la factura de la luz.

It is the most recommended option for continuous use. In addition, they usually have a display and buttons to control the temperature or even program its power every hour for every day of the week, so once programmed we will completely forget about it and save even more.

Comprar - Thermal emitters

Oil coolers

Oil radiator

Oil radiators are quite heavy because inside there is a high density oil that we have to heat. This has the disadvantage that it will take a long time to start noticing that it gives off heat and also needs much more energy than in the case of thermal emitters.

The advantages of oil radiators are that they are very cheap and that once they are turned off, as the oil is hot, it will be giving off heat for several hours without wasting any electricity.

We only recommend this type of radiator if you do not want to spend a lot of money and have to use it to heat a single room.

Comprar - Oil coolers



The heater is usually very inexpensive and has high power ratings for immediate heating of small rooms such as a bathroom, which is ideal for use while showering.

Although it heats quickly, it is not very efficient so it is only recommended to use it for short periods of time, so it is ideal for bathrooms or rooms where we have to do some kind of activity for a few hours.

In addition, since they weigh very little, they can be easily transported and stored.

Comprar - Heaters

Heat pump

Heat pump

Heat pumps are also known as air conditioners or split air conditioners. In spite of operating with electricity, they are very efficient since they have a great heating capacity (depending on the quality of each model) and thanks to the Inverter technology they consume energy in a moderate way, being able to heat large rooms without any problem.

As the only drawback, the heat pump has a high price (from 300 euros for basic models with a few frigories) and requires installation, which is another cost to add. As an advantage, besides using it to provide heat in winter, we can also use it in summer to keep the room cool, dehumidify or use it in fan mode only.

If your budget allows it, it is one of the most recommended options for permanent use.

These are broadly the most common types of electric heating. If electricity is not an option for you, we recommend that you look at alternatives such as blue flame, catalytic or even kerosene stoves.

Advice on how to save on electricity

Radiator power

Due to life circumstances, I have had to switch to electric heating for a three-storey semi-detached house in which we will use only the following rooms:

  • 2 Offices (second floor)
  • Bedroom (second floor)
  • Bathroom (second floor)
  • Kitchen (second floor)

The rest of the house remains closed, both at the level of shutters and doors. In this way we avoid that the cold they have is transferred to the hot area of the house and the radiators lose efficiency.

In terms of electric heating, we have opted for with the following configuration:

  • Office: 1 800W radiator
  • Office 2: 1 500W radiator
  • Bedroom: 800W
  • Stove: 1300W
  • Lobby: 1 x 500W radiator

In total there are 5 radiators that add up to a power of 3900W and heat the house evenly. In addition, as the heat rises, the attic gets warm without the need for any heating while the first floor, which is the coldest, is kept warm with the combo of the two 1300W + 500W radiators.

In terms of electricity it can be a ruin but having to change the gas installation and renew the boiler, it was not profitable to invest more than 2000 euros at once to spend a single winter so the solution was to use electricity.

In order to save as much as possible, I contracted a tariff with hourly discrimination in which I get 8 hours a day with a very reduced price of Kw/h. Specifically, I went from a Kw/h price of 0.15 € cents to 0.08 € cents, so the savings are remarkable.

These 8 hours are distributed as follows:

  • From 9:00 a.m. to 3:00 p.m.: we heat the house with the radiators on full blast and at a temperature of 24ºC, since the cost of electricity is much lower.
  • From 15:00 to 17:00: we switch the radiators to ECO mode and a temperature of 21ºC. As we have reached 24ºC in the previous period, they will hardly turn on and we will have a comfortable temperature.
  • From 17:00 to 19:00: we used up the two remaining hours of cheap electricity to warm up the house again and recover the temperature in case it had dropped.
  • From 19h we have a tariff at 0.16 € Kw/h but again, the radiators will operate in ECO mode so they will hardly turn on and we will arrive at night with the right temperature.

We also take advantage of the heat given off by household appliances. Simply using the dishwasher is already a good heating since for an hour it is running at a constant 50ºC and then leaves a residual heat that is maintained for several hours, so it all adds up.

In the long term it is clear that natural gas would have been a more economical option but not in the short term. In addition, we can always sell the radiators once the winter is over, so you recover a large part of the investment made.

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