Efficiency has always been at the forefront of wood burning stove design.
Wood stoves are a popular replacement for traditional open wood burning fireplaces as they can help to increase the heat output from burning firewood in your home.
Efficiency of a wood stove can affect how much heat is being produced from every piece of wood, and so are wood burning stoves efficient?
Wood burning stoves can be very efficient at burning firewood compared to other types of fireplace. Efficiency ratings of wood stoves can be between 60% and 90% depending on the model of stove, while the efficiency of open wood burning fireplaces can be as little as 10 or 20%.
Wood stoves have been designed to help overcome the flaws that are present with burning firewood inside traditional open fireplaces.
As the efficiency of an open fireplace can be so poor, wood stoves can be a solution to help increase heat output and to help reduce emissions and fuel consumption when burning wood.
We’ve explained in more detail below using our own stoves as examples:
- How efficient wood stoves are
- What makes wood stoves efficient
- How wood stoves can be used efficiently
Are Wood Stoves Efficient?
Using a wood burning stove can be a more efficient alternative to burning wood inside traditional open fireplaces.
Stoves are commonly installed within open fireplaces to help increase the efficiency and heat output from burning firewood in your home, but can also be installed in many other locations in a home where they can be accommodated.
In terms of efficiency, the Environmental Protection Agency explains that open wood fireplaces can have a very poor efficiency:
‘Most traditional open fireplaces lose over 90% of the fire’s heat out the chimney.’EPA
An open wood burning fireplaces can be very inefficient at producing heat for your home because much of the heat can be lost up the chimney instead of being transferred out into a room.
Much of the heat that could be generated from burning wood can come in the form of burning off the waste gases produced from the initial combustion of the wood. These gases leave an open fireplace quickly and so there’s no environment for them to be burnt to produce even more heat.
Open fireplaces also aren’t great at radiating heat. You may find that you’re having to sit nearer to an open fireplace to feel the heat, and won’t be able to feel as much warmth if sitting across the room.
Finally, the uncontrolled air supply to open fireplaces can mean that much of the warm air from a home can be pulled up the chimney, and in many cases reduce the temperature of a home rather than increase it.
Wood stoves are therefore designed to help overcome these issues.
Wood burning stoves help to resolve these issues by:
- Keeping waste gases inside the firebox for longer and under higher pressures and temperatures to allow more heat to be produced through secondary combustion of these gases.
- Using air vents to control the air supply to the fire and therefore help control how efficiently the fire is burning.
While open fireplaces can be as little as 10 or 20% efficient at burning firewood, the majority of wood stoves can be found with efficiency ratings of between 60 and 80%, with some models even reaching into the 90’s for efficiency.
As an example, we have two stoves. One stove has an efficiency rating of 71.6% while the other has a rating of 78.9%.
This means that our stoves have been rated as efficient.
Some models of wood burning stove will have a higher efficiency than ours, while others will be less efficient. You can expect to have to pay more for wood stoves that have higher efficiency ratings, as it can require further research and design to increase the efficiency even higher.
However, a higher efficiency rating stated on a stove doesn’t always necessarily mean more heat being produced and less wood being used.
The EPA explains that there are two different types of efficiencies used to describe how well a wood burning stove converts fuel into heat.
- Combustion efficiency
- Overall efficiency
Combustion efficiency describes how well a stove converts the fuel into heat.
Overall efficiency describes how well a stove transfers that heat out into a room.
The EPA also explains that overall efficiency is a better measure of how well a wood stove converts firewood into usable heat for your home.
To check the actual overall efficiency of a wood stove you can look a stove up on the EPA’s database of certified wood stoves.
In the UK you can view DEFRA’s list of approved stoves for actual efficiency ratings, and more information about DEFRA approved stoves can be found here.
Efficient Wood Stove Design
In order to overcome the typically poor efficiency of open fireplaces in terms of being able to transfer heat from burning wood into a home, wood burning stoves incorporate a number of unique designs to help them be more efficient.
These efficiency-improving designs include:
- A baffle plate
- Controllable air vents
- Steel or cast iron body
The baffle plate is located inside the top of the firebox inside a wood stove.
A baffle helps to slow down the rate at which waste gases leave the firebox, thanks to a small gap that they must pass through. With higher temperatures and pressures created inside a stove these waste gases can be burnt off to produce even more heat through secondary combustion.
We’ve explained wood stove baffle plates in more detail here.
The air vents on a wood stove can be adjusted allowing you to control the amount of air getting to the fire and therefore controlling the heat output and efficiency of the fire.
By restricting the airflow into the stove you can improve the efficiency of the fire and ensure that the firewood isn’t being burnt too quickly.
The bodies of wood burning stoves are typically made of steel or cast iron. Both of these materials are great conductors of heat and allow a stove to radiate much more heat out into a room compared to a traditional open fireplaces.
How Do You Use A Wood Burning Stove Efficiently?
Even if a wood burning stove has been classed with a high efficiency rating, if the stove isn’t used in the right way then the firewood can still burn too fast and hot to be efficient.
A wood stove isn’t burning efficiently if:
- Too much air is being supplied to the fire and it’s burning through the wood too quickly.
- Too little air is being supplied to the fire and is smoldering and struggling too much from incomplete combustion of the wood.
For our detailed guide on how to use the air vents to control a wood stove click here.
When using a wood stove efficiently you’ll want to maximize the amount of heat being produced from every single piece of firewood.
In order to achieve this you’ll need to close down the air vents when the fire has got going until the fire is burning through the firewood calmly.
An inefficient fire in a wood stove is one that is burning too quickly with roaring flames or burning too slowly and smoldering.
Wood burning stoves are very efficient at burning firewood to produce heat thanks to a number of efficiency-enhancing designs such as baffle plates and controllable air vents.
The average efficiency rating of a wood stove can be between 60% and 80% but can be higher or lower depending on the model of stove.
A wood stove will be able to generate much more heat compared to using a traditional open wood burning fireplace.
The actual efficiency ratings for EPA or DEFRA approved wood stoves can be checked on their respective websites.
A wood stove needs to be operated efficiently in order for a stove to actually be efficient at converting firewood into heat.