Heat output explained – how hot is your wood burner? 

Knowing how hot you can burn is crucial to keep your home warm safely. Whether you’re looking for a new log burner or you’re wondering how to get the most from your stove, understanding how heat output works will make sure you’re always heating your home safely – and getting the most heat for the least fuel.

What does kW mean? 

One of the top pieces of information your log burner will come with is its heat output, measured in kW (kilowatts). This number is the maximum heat output capacity of your stove under laboratory conditions – your 5kW stove does not always give out this amount of heat. 

Think of your wood burner’s kW rating like a car’s top speed – just because your car can reach 120mph, it doesn’t mean you will always be driving at this speed. Your 5kW stove’s rating shows its maximum potential, but during everyday use you’ll use much less. 

Your 5kW stove doesn’t always burn at 5kW 

Most of the time, you’ll be running your log burner at only a portion of its maximum heat output. A 5kW stove will usually operate between 2-4kW during a normal evening of heating, reaching closer to 5kW when fully loaded and your fire is well-established. 

The amount of heat your stove will give out will depend on a variety of factors, such as the amount of fuel you use, the quality of the fuel, and how you adjust the air controls. 

Got a larger room but think a 5kW wood burner will be enough? Speak with your local HETAS Approved Retailer – they will make sure your new stove heats your room evenly and keeps you warm. 

Small, standard, and large stoves

The definition of the sizes of stoves will vary on who you ask, but there are generally three ranges of appliances based on their heat output: 

Small stoves: typically 3-5kW, stoves on the lower end of this scale are great for small rooms (and narrowboats), well-insulated places that keep heat well, and as a secondary, supplementary heat source. 

Standard stoves: usually 5-8kW, stoves in this range of the most popular choice across the UK. In a house with standard insulation, an average-to-larger-sized living room, or an open-plan living space, these do a great job at keeping most UK homes warm throughout winter. 

Large stoves: generally 8kW+, these large stoves are used in large, open-plan houses as they are able to give out a lot of heat. Stoves capable of this level of heat output are also used in older, poorly insulated houses that have large, open rooms – such as converted farmhouses or older properties.  

These are general categories – it is important to remember that there are multiple factors beyond room size that will affect which size log burner is right for your room. 

Cleaner Choice stoves to choose from 

All Cleaner Choice certified appliances have been independently verified to produce at least 50% less harmful particulates than the stringent legal requirements in the UK. 

Choosing an appliance that has the Cleaner Choice mark gives you peace of mind that you are burning efficiently, safely, and cleaner – and there is a wide range to choose from, whether you’re heating a small, cosy room, or a large, open-plan space. 

Small

Standard

Large

Extra large

What can affect your heat output? 

Your stove can only perform to its maximum potential with proper care and responsible use. There are three overarching reasons why your stove may not be burning the way you expect it to: 

1. Poor burning habits

• Using wet wood (look for the Ready to Burn mark when buying firewood) 

• Overloading your stove or not burning enough 

• Not regulating your airflow using your air controls 

• Burning material that should not be burnt 

• Leaving the stove door open whilst you burn 

2. Lack of chimney maintenance

• Soot, tar, and creosote buildup stops smoke from escaping your chimney 

• Blocks in the flue restrict airflow, affecting the quality of your burn 

• Damaged flue liners will negatively impact the performance of your fire 

• Birds nests and other debris has the potential to catch alight, damaging your chimney 

3. Inadequate servicing

• Old, worn-out stove rope will allow too much air into your fire 

• Damaged internal parts will weaken the intensity of your burn 

• Internal buildup of debris and creosote deposits will lead to further damage 

You will not only be getting less heat from your log burner if any of the above apply to you – you’ll be risking your safety. Responsible burning and regular maintenance from a trained professional makes sure you’re always get the most heat from your fuel, and it isn’t just smoke up your chimney. 

Choosing the right stove 

For more information on some things to think about when selecting your new log burner or multifuel stove, look through our checklist on how to choose your perfect wood burner. 

You’ll need to think about heat output, efficiency, safety, where you live, and the aesthetic you want in your home. 
 

Understanding heat output will let you not only choose the right log burner, but also know how to use it efficiently – giving you more heat for less fuel. Keeping up with regular maintenance and consulting a professional HETAS registrant if you’re ever in doubt will help you stay safe and warm this winter.