What is the most efficient outdoor wood boiler? Here’s how to know (LHV vs HHV)

Like in all things, you probably want the best. When it comes to heating, that means a high efficiency wood boiler.

But when it comes to high efficiency wood boilers, how do you know for certain, what is the most efficient outdoor wood boiler?


Your vehicle used to have better fuel mileage in Canada than in the US.

In an effort to understand why, you might already be imagining it has something to do with our roads, the wind, or a difference in the manufacturing process.

But nope.

In the past, Canada used the Imperial Gallon, which is slightly larger than the US Gallon.

So, a car salesman in Canada could say the same truck in his lot did 5 more miles per gallon than the same truck in the lot across the border.

It’s the same for measuring efficiency in a high efficiency wood boiler.

In your search for the most efficient outdoor wood boiler, it’s important to spot the different measurements manufacturers use.

If you want to cut to the chase, look for the Higher Heating Value (HHV) rating. It’s the gold standard for determining the most efficient outdoor wood boiler!

In fact, the EPA requires that all manufacturers report their efficiency using the HHV.

However, like comparing an Imperial Gallon to a U.S Gallon, it could be tempting to use the Lower Heating Value (LHV) to make your efficiency rating seem higher.

Don’t be fooled!

Check the fine print to make sure you know the HHV, and the true efficiency rating of the most efficient outdoor wood boiler.

When it comes to high efficiency wood boilers, what’s the Difference Between the Higher Heating Value (HHV) and the Lower Heating Value (LHV)?

The difference comes down to the math.

In the HHV mathematical equation, the energy required to evaporate the wood’s moisture content is taken into consideration.

The LHV equation doesn’t take moisture into consideration. So using the LHV can artificially inflate your efficiency.

Be careful when someone starts talking about efficiency in a high efficiency wood boiler using the LHV, it’s like trying to say your truck gets more miles to the gallon by using Imperial Gallons.

We don’t make ultra-efficient outdoor wood furnaces for the accolades, we do it to save you time and money cutting and seasoning wood.

BUT we are incredibly proud of our engineering team and their achievement with the G10000 reaching the #1 spot on the EPA’s efficiency chart.

And again, while there are different metrics to measure efficiency, the toughest test remains the higher heating value.

And the G10000 leads the pack with 88%.

The G4000 is not far behind in a tie for second place at 86%.

Check it out for yourself on the link to the EPA website below, and search for “Cord Wood”.

Make sure to hit ‘sort’ below the Overall Efficiency-HHV (%) column.