Heat Output Calculator

You can use the calculator below to guide you as to the size of wood burning stove that you will need to heat your room. Please note, that this is a guide only, see the full description of stove kw output classifications below for further information on choosing the right size stove for you. Read more...

Output Calculator

How well insulated is your house?

Is the room open plan?

Do you like the room warmer than 20°C?

kW's needed
We recommend looking for stoves between:

Stove Output Calculator

If your room needs a stove that is between 4-6kw then browse our Small Wood Burning Stoves Range

If your room needs a stove that is between 7-9kw then browse our Medium Wood Burning Stoves Range

If your room needs a stove that is between 10-15kw then browse our Large Wood Burning Stoves Range

How to use this calculator

It is important to use the results obtained above as a guide only. We suggest not only look for a stove with the exact output power, but consider other stoves within the range suggested (see the sections below on output power for more information).

  1. Enter the dimensions of your room.
  2. Select how well insulated the room is:
    1. As a general rule houses built after 1990 or houses that have been insulated with new double glazing, cavity wall and loft insulation etc., fall into the well-insulated category.
    2. The standard insulation category should be used if you are in any doubt, but in general houses built before 1990 or well insulated houses with large external windows or a large percentage of external walls could fall into this category.
    3. Finally use the poorly insulated house if your house is older, has no double glazing and loses a lot of heat if very drafty.
  3. If your room is open to an adjoining room or has an open staircase, tick the relevant box.
  4. The general calculation allows for a temperature of about 20 degrees; if you like your room to be warmer, tick the relevant box.

What is output power and how accurate is it?

The output power of a wood burning stove is measured in kw’s, much like radiators and electric heaters. This is a guide as to the power that the stove will put out each hour into your room – therefore a 5kw stove for instance will deliver about 5kw’s of heat per hour into your room.

It should be pointed out that this is a tentative guide when it comes to wood burning stoves. Stove manufacturers actually choose the kw output that they want each stove rated at and they are then tested for efficiency once the designated heat output is reached. Therefore two things are true of stoves:

  1. All stoves can give a range of heat outputs depending upon a large array of factors including how much fuel you put in the fire box, the type of fuel used, the draw of the chimney etc. The list goes on, but in fact there is a simple factor – the more wood you can burn, the greater the heat output.
  2. The efficiency rating of every stove changes depending upon how much heat it is producing. Some manufacturers re-test their stoves at several different kw outputs to get the best efficiency rating. The stated efficiency ratings are therefore only at the rated power output.

What is the difference between Nominal and Maximum output power?

To make things slightly more complicated, stoves have both nominal and maximum heat output ratings. Nominal output is what the stove has been rated at with its associated efficiency rating but this may well not be the most heat that you can get out of the stove. Where stoves have a maximum output, this is a more reliable figure and shows the most heat that the stove will produce under test conditions. Of course with a different set up and different fuel, this could change in your home but it is more constant and reliable than the nominal output rating.

Accordingly, where possible, we have used the maximum output on this site as a guide.

What fuels are there and what difference do they make to the output?

Some of our stoves will only burn wood but there are still different qualities of wood. Well-seasoned wood should always be used as any moisture in your wood will have to be burnt off before you get any heat out of the stove and the moisture will also attack your stove and flue parts reducing their life. Hardwood as a rule burns longer but different wood will burn at different rates and temperatures.

Where a stove allows you to burn coal as well, these multi-fuel stoves give a bit more flexibility. There are several different types of coal, including man made and naturally occurring fuels, all of which have different properties and burning temperatures. Anthracite coal is a natural smokeless coal and it burns very hot, so can be used to maximise the heat output from a stove and coal is always recommend for overnight burning.

For more information on the different types of fuel and their properties see our technical section on fuel.