What Size Oil Filled Radiator Do I Need?

Find The Right Size Oil Filled Radiator For You


In this guide, I will show the most common oil filled radiators output and what size room they heat, as well as how you can work out what size oil filled radiator you need for any room in your property.

There are many factors to consider when determining the right size oil filled radiator that will provide sufficient heat in your property. The size of the oil filled radiator that you need will depend on two main factors, which are:

  • Room size
  • Room Insulation

Room Size For The Right Size Oil Filled Radiator

The first thing you need to do is figure out your room size in square meters. If the room is 4 meters x 5 meters or 3.5 meters x 5.5 meters, this will be 20 square metres.

You take the width in meters x length in meters, and this will give you the square meter size of your room.

If your ceilings are quite high, whatever the wattage is required for standard ceilings, add another 500 watts to be on the safe side.

Once you know your room size, the next thing to consider is how well the room/property is insulated, we will look at this in more detail below.

Room Insulation For The Right Size Oil Filled Radiator

How well insulated your room is will make a huge difference. If you have really poor insulation, such as single glazed windows, solid brick walls and so on, you may want to add another 500–1000 watts, as the room will be losing heat faster than it can retain it in the room, and the only way to keep the room warm is by increasing the heating power output from the oil filled radiator, an inadequate oil filled radiator will take longer to warm up your room.

If you live in a modern property, you will have very good insulated cavity walls with double glazing and low ceilings, you will have no issues heating your room with the recommended size, and most likely not have to use it on full power.

Your average property, with average insulation, double glazed windows will be perfect for the recommended rooms size for oil filled radiators.

What Size Oil Filled Radiator Do I Need?

With taking the above room size and insulation into account, below I will show you the most common wattage oil filled radiators, and what size rooms they will heat, this will help you determine what size oil filled radiator you need.

  • 500w oil filled radiator room size = 5 SQM
  • 800w oil filled radiator room size = 8 SQM
  • 1000w oil filled radiator room size = 10 SQM
  • 1500w oil filled radiator room size = 20 SQM
  • 2000w oil filled radiator room size = 25 SQM
  • 3000w oil filled radiator room size = 30 SQM

The above are suitable for average to excellent insulated rooms, poorly insulated rooms should go for the next one up, for example, if your room is 20 SQM, get a 2500 watt oil filled heater to ensure the room gets warm. Getting the right size heater, will ensure your oil filled heater is cheaper to run, and you get the best oil filled radiator for your room.