We often get asked about stove sizing. Whilst it contributes to the aesthetic of the stove, the size will largely be determined by what output is appropriate for you. HETAS installers currently use the following guide to help customers select the appropriate heat output.

The two most important factors are how big the room is and how well insulated it is. Smaller rooms need less heat to reach a comfortable temperature and more highly insulated rooms retain their heat for longer. You also need to consider and allow for your lifestyle considerations, such as if you often keep a window open in that room, or if the room is open plan or has a staircase.

To start calculating the stove output we need to measure the room. Using a tape measure, write down the length, width and height of the room in meters. Multiply these numbers together to give your room volume.

For example = 4.5m (length) x 5m (width) x 2.4m (height) = 54m³

Once we have a value for the room volume we can multiply it by an insulation factor. This insulation factor takes into account how much heat is lost from the room.

We can use the following table as a guide to selecting the insulation factor and this will give us a kW value for the ideal stove output.

Approximate Room Size

Older poorly insulated.

Typically pre 1950's

Moderately insulated.

Typically 1990's

Modern well insulated.

Post 2008 construction

≈ 28m³ 0.11 0.069 *See Notes
≈ 57m³ 0.10 0.055 0.039
≈ 85m³ 0.09 0.050 0.036


Using the example presented above, our room volume was 54m³ and its an older home, not well insulated. We should therefore select the insulation factor of 0.10

54 x 0.10 = 5.4kW

This tells us that we're going to need a stove with an output around 5.5kW. This figure may need adjusting based on the lifestyle considerations we mentioned before. HETAS give guidance that if your home is in an exposed location then it could suffer from above average heat loss and you should therefore allow an additional 10% to the kW figure calculated. It's also important to remember that you want an appropriately sized stove working at capacity rather than a stove that is too big and can't be used effectively because it's too hot for the room.

At Ambience: Fires & Stoves we will always carry out a home visit to check that a selected stove will be suitable. The above information is a useful guide but our experienced surveyors can assist you in finding the right stove. We have a range of stoves that can meet all needs!

*Note for modern well insulated houses*

These will only require a small amount of heat to maintain living temperatures. The guidance figures above will, in most cases, still suggest an output below that which is offered from most nominal stated outputs. Customers wishing to install solid fuel stoves in these properties should be made aware that excessive heat is likely to be generated. Thought should be given to ducting off convected heat to other rooms.