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HHV vs. LHV - Learn Kuma 2020 Wood Stoves

You are shopping for a wood stove and you have decided that efficiency is important! You want to get the maximum amount of heat out of every piece of wood that you put into your stove.

If you don’t want to take a deep dive into the math or science behind stove efficiencies and you just want an honest value to compare then just ask to see the HHV (high heat value) efficiency of any stove you are researching.

1. HHV is accurate: The HHV method accurately recognizes that all wood has some moisture in it - this is why HHV efficiency is lower than other methods.
2. HHV is Independently Tested: All stoves are tested by an independent laboratory. These test reports are readily available and average efficiency is usually stated in HHV
3. HHV is used by the EPA: The EPA calls it “overall efficiency” and the values listed in their database are always HHV

In a nutshell - What is HHV and LHV?

Higher Heat Value: HHV uses all of the heat contained in the wood when calculating efficiency.  This is sometimes called the “Gross Value” or the “Higher Value”

Lower Heat Value:LHV uses only some of the heat contained in the wood when calculating efficiency.  This is sometimes called the “Net Value” or the “Lower Value”

Is LHV a misleading calculation?
Not at all. They are just different, in fact, a wood stove with a great HHV Efficiency will also have a great LHV efficiency.
All wood has some moisture in it. All stoves will consume some of the wood’s energy to evaporate that moisture. HHV Efficiency reflects that reality and is just a better representation of how efficient a stove will be in your home.

When Comparing, use the same values, ideally HHV.
It is confusing when you have to compare 2 products and one product lists the LHV efficiency and the other product lists the HHV efficiency. Worse yet, some products do not list which method they are showing you so you are left to guess.

Always ask to see the High Heat Value (HHV) efficiency of any appliance that you are researching. This value is published by the US Environmental Protection Agency and is a true representation of how your stove will perform in your home.