How many watts would i need for a room?

How many watts would i need for a room?

I’m not sure how many watts of electric heaters needed for a room, do you have any suggest?


First of all, please make sure you want the whole room to be warm, rather not just want to warm a specifical area of the room.

The room we are talking in this article is a open-space room.


Before giving clients propose, we have to consider some factors,

1.       the room size

For standard ceiling height such as 2.8m, heating the room temperature to be 16-20 degree C, it needs 25 to 45W per cubic meter. For large open-space room such as more 80 sqm, the bigger the size is, the more watts per cubic meter needs.


2.       the ceiling height

We know heat always transfers from lower position to higher, so ceiling area is normally the second hottest position of one room, of course the hottest area is closing to the electric heater.

This means if a room ceiling is very high such as 3.5m, then most of the heat will rise to the top layer of the room, there will be little heat around the floor height. This will surely need much more watts to make the heat transfer down to lower position.

For such room condition, we suggest users to add a suspending ceiling at the height of about 2.6m.

In this way, much electricity will be saved.

If unfortunately suspending ceiling can not be added, we suggest to use under flooring evenly heating cables or film.

If under floor heaters are not suitable neither, please consider infrared heaters.


3.       the insulation condition

The importance of this factor is obvious, good insulation room such as with 2 layers glass windows will absolutely keep the heat staying in the room.

For poor insulation condition room, please consider to add foam panel or similar panels/sheets to the wall; try to replace the windows with double layers glass.


4.       the weather of the area and the time

1)the local weather

Taking an example, in winter same date, there are two same rooms with 9 sqm size and 2.6m ceiling, same insulation condition, room A is in Russia while room B in Hong Kong, a 800W electric heater can heat room B to 22 degree C while heating room A to be 15 degree C only.

The colder the local weather is, the more watts a room needs.

2)the season

For some special usage such as hot yoga studio, they need the room to be hot even at summer,

Obviously it needs less watts to heat the room to be 38 degree C is the weather of that time is 30 ℃.


5.       the room temperature wanted

Obviously the hotter you want your room, the more power you need.

Usually in winter 15-20 room temperature will make people feel cozy.

There are two points users should notice,

1)     The temperature degree is not directly proportional with watt, for example a 800W electric heater warms your room to be 20 degree C, and a 1200W one heats it to be 25 degree C, does this mean if you want your room to be 30 degree C, then the electric heaters should be 1600W? The answer is NO!

The higher temperature you want, the more watts needed to raise the temperature bye one ℃.

2)   To heat such as 9 sqm room to be 20 ℃, a 1000W electric heater will work, it does not mean a 800W can not make it. This is just heating time difference, means the 1000W heater takes 40 minutes to heat the room to be 20 ℃, the 800W heater can make this as well, but it needs more time such as 60 minutes.


Finally let’s take a general example, such as middle Europe winter weather, a living room with normal insulation condition, 2.8m ceiling height, it needs about 90W per square meters, to warm the room to be around 20 ℃. Of course you can also use 80W or even 70W per sqm, that will be just a problem of needing more time.





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