Biomass Boilers - Everything You Need to Know

As the UK continues its drive to reach net-zero emissions, fossil fuels like gas and oil are being challenged by greener alternatives.

This is especially true when it comes to heating our homes, which still predominantly use gas-powered boilers to keep us warm.

By 2035, the UK government wants to have phased out roughly 80% of gas boilers (it’s still not clear if the government is actually committing to the gas boiler ban however), so finding an alternative in that time might become more pressing for UK households.

One alternative is something called a biomass boiler.

We’re going to give you everything you need to know about biomass boilers here in this article, including what they actually are, how they compare to gas boilers, how much they cost, and whether it’s worth getting one or not.

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What are biomass boilers?

Biomass boilers are similar to gas and electric boilers in that they provide heat for a home, but that’s where the similarities stop.

Unlike gas boilers, biomass boilers don’t burn gas as fuel — instead, biomass boilers burn wood pellets, chips, or logs, which (ideally) all come from sustainably sourced trees, or another type of organic matter.

These pellets, chips, or logs are burned in a stove and used to either heat an individual room, or to heat water that’s then funnelled around your home’s radiators, keeping you warm and toasty just like an ordinary boiler would.

Some models must be topped up manually, and some models will automatically supply the stove with fuel via a fuel hopper. You can usually programme this fuel hopper to top up your biomass boiler at intervals of your choosing — this is great for when you have high heat demands during the colder months.

Are biomass boilers better for the environment than normal boilers?

On paper, a biomass boiler is better than your typical gas boiler — after all it’s burning a renewable fuel source, typically wood, and not a finite fossil fuel (which most boilers in the UK still rely on).

However, a biomass boiler isn’t completely without harm to the environment, nor the environment within your own home (unless you install the right equipment to stop particulates polluting the air inside).

Unlike solar, hydro, and wind power, biomass is a renewable energy source that isn’t free from emissions, as noted by the UK government in its review of the fuel source. But how much would be released into the atmosphere from using a biomass boiler?

So with a bit of napkin maths, a biomass boiler will emit around 598 kg of CO2 into the atmosphere each year.

Compare this to the 2.2 tonnes of CO2 released each year by homes with gas boilers and you can see the benefit of using a biomass boiler from an environmental standpoint.

Biomass boilers aren’t as good for the environment as heat pumps though, which can be wholly powered by a renewable energy source and have practically zero emissions.

How efficient are biomass boilers?

Biomass boilers, especially modern ones, are almost as efficient as the most efficient boilers. Honestly, at the top level, it’s so close as to barely make a difference:

A Viessmann Vitodens 200-W combi boiler has a market-leading efficiency of 98%, and a Grant Spira biomass boiler comes second (just) with its 97.4% efficiency rating.

So there’s barely a hair’s breadth between these two, but you should note that this is at the top level of efficiency. It’s a slightly different story for biomass boilers in general, because unlike gas boilers, they’re not legally required to hit an efficiency rating of at least 92%.

Meaning when you compare the lower limits of biomass versus gas boiler efficiency, you’ll find biomass boilers with efficiency ratings as low as 80%.

You’ll be wasting 20p for every £1 of fuel you put into a boiler with this level of efficiency, and as a general rule of thumb, the more efficient a boiler is, the less money you waste.

Just to be clear as well, there are loads of biomass boilers with efficiency ratings comfortably over 90%, it’s just worth doing a little bit of research before you make a purchase.

How much does a biomass boiler cost?

A biomass boiler isn’t cheap, with most basic models starting at around £5,000, all the way up to £20,000 and beyond for a top-of-the-range, fully automated pellet boiler.

You’ll also spend another £2,000 or so installing a biomass boiler, so keep that in mind when considering what you want to pay overall.

What does running a biomass boiler cost?

The cost of running a biomass boiler depends on the fuel used:

Wood pellets are the most efficient type of fuel for a biomass boiler, as they burn for longer (they’re more dense). At roughly £190 a tonne, a large house will spend close to £950 a year to keep warm.

Which might sound a lot, but it’s only a little over the average UK spending on gas heating — around £880 a year for a typical three-bedroom property (as of October 2024). And if the price cap rises again, biomass fuels will likely be cheaper than gas (they’re not as affected by fluctuating energy prices).

If you look at the bigger picture, biomass is actually much cheaper than the high costs involved in extracting fossil fuels. You can quite literally grow biomass as a crop and burn it to keep your home warm! Pretty clever right?

The different types of biomass boilers

Although all biomass boilers work by burning, well, biomass, not every boiler uses the same type of biomass fuel. Let’s look a the different types of biomass boilers:

Pellet biomass boilers

Pellet biomass boilers burn pellets made from compressed organic material, typically wood, plant materials, or sawdust. Sometimes, pellets can be made from animal dung! Don’t worry, there are zero odours if you use this as fuel.

Most biomass boilers using pellets will automatically refuel themselves, making pellet boilers a lot easier to refuel than a log-burning boiler.

Unfortunately, convenience comes at a cost and pellets are the most expensive type of biomass fuel you can buy.

Pellet biomass boilers are best suited to small and medium-sized properties.

Wood chip biomass boilers

Wood chip biomass boilers using chippings of wood considered too small to be useful in industry. It’s a good way to make use of wood that’d otherwise go to waste.

This type of fuel is cheap, but generally has a lower energy density than wood pellets. If you decide to use recycled wood chips, you should be especially careful of contaminants such as laminate, plastic, and paint.

Wood chip biomass boilers are best suited for larger homes.

Log biomass boilers

Biomass boilers fuelled by logs have to be filled by hand to keep burning, which can be a decent amount of manual labour. Logs are pretty inefficient too, so you’d struggle to heat a whole house using logs.

If you did try to heat a whole house using logs alone, you’d be burning a lot of them; for a long time as well.

For that reason, log boilers are best suited to smaller properties and in an ideal scenario, homes near a plentiful supply of logs.

What is the best biomass boiler?

The best biomass boiler can change depending on your circumstances. For example, if you live near a forest and have an easy supply of logs, it makes perfect sense to get a log-burning biomass boiler instead of one that relies on costly pellets.

You might instead prefer a biomass boiler that does the refuelling for you, saving you time and effort. In that case, a Viessmann Vitoligno 300-C or a PBI 36 kW biomass boiler are great choices. All you do is top up by a large amount every now and then, and the boiler will automatically refuel itself from this pellet cache.

Here are our picks of the best biomass boilers you can buy right now:

• Viessmann Vitoligno 300-C: Best for automated features (£9,000–£10,000)

• Grant Spira: Best for efficiency (£11,000–£21,000)

• Froling T4e: Best for power output (£15,000, or more depending on output)

• Windhager LogWIN Premium Touch: Best log boiler (£12,500)

• La Nordica Luisella Pellet Boiler: Best for affordability (2,000–£3,000)

Advantages and disadvantages of biomass boilers

Biomass boilers, like any type of heating technology, come with their pros and cons. Let’s take a look at the advantages and disadvantages of biomass boilers, before breaking them down in more detail:

Pros:

• More environmentally friendly than gas boilers

• Can qualify for a government grant

• Not that expensive to run

• Can be used in off-grid setups

Cons:

• Still releases some emissions

• Considerably more expensive than most boilers

• Can require trees to be cut down for fuel

• Takes up storage space (for fuel)

• You’ll need to install a flue pipe

We noted before that biomass boilers are better for the environment than gas boilers, but that they’re still not fully green because emissions are still released. This might be a deciding factor for you in choosing to get a biomass boiler, as despite using a renewable energy source (biomass), it won’t be as eco-friendly as you might expect.

You’ll need to make sure you install a stainless steel flue pipe too, which will release the carbon emissions and particulates you don’t want polluting your home. You could also use an existing chimney, but check with your installer to see if your chimney qualifies legally (it must be insulated to a certain degree).

Also, though biomass boilers cost a good deal more than typical gas/electric boilers, you could still qualify for a government grant. Namels, the Boiler Upgrade Scheme, which provides eligible homeowners with a grant worth up to £7,500.

This won’t cover the full cost of the most expensive biomass boilers, but it will make affording one a lot easier!

And once you have a biomass boiler, the running costs really aren’t that bad. A downside though is that biomass fuel takes up storage space (potentially up to two or three metres cubed(m³) if you plan to buy in bulk. Especially if you use logs, which take up a lot more space than pellets.

Lastly, biomass boilers are great for off-grid setups that can’t connect to the gas mains, if you can afford one. An alternative is an LPG boiler, which is a type of boiler that uses liquified petroleum gas (LPG) and is definitely a cheaper option.

Is it worth getting a biomass boiler?

Despite the high upfront costs, a biomass boiler can be a good alternative to standard, gas-powered boilers. They release less emissions overall, aren’t subject to volatile price rises (like gas can be), and can be almost as efficient as the most efficient gas boilers.

They last longer on average than a gas boiler as well — 20 to 30 years for a biomass boiler, versus 10 to 15 for a gas one.

However, for most UK homes, it’s probably not worth spending many thousands more on a biomass boiler. Modern combi boilers are incredibly efficient, have much smaller upfront costs, and take up a lot less room.

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