Category - Boilers
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Will Scholfield, Engineer

31 Oct : Updated 4 Apr ● 9 min read

Biomass vs gas boilers: Which is best for your home?

Considering whether to switch to biomass? Or should you remain with a gas boiler? From cost, to space, to environmental factors, deciding whether to choose a biomass or gas boiler can be difficult.

In this guide, we'll be going through and comparing these two boilers to see which one is right for you. At BOXT, we want to ensure you have all the necessary information to make a choice that suits you and your needs.

So, let's take a look at these two boilers to see which one is best for your home. 

How do biomass boilers work?

Biomass boilers are a renewable energy source that burns wood pellets, plants and other natural waste to generate heat for the home. They work similarly to other standard boilers, except they do not burn fossil fuels like gas, oil or coal.

The heat goes through a combustion chamber, turning it into a hot gas. This gas travels through the flue duct and heat exchanger, where the heat is absorbed by the water running through your central heating system.

How do gas boilers work?

As the name suggests, gas boilers run on natural gas or liquid petroleum gas (LPG) and are the most common type of boiler in the UK.

When a boiler burns natural gas, it must come through an underground network of pipes. On the other hand, LPG can be stored in cylinders that need replacing regularly.

The gas is burnt and the heat produced is transferred via a heat exchanger into the primary water of your central heating system. This heat in turn is then either used to heat spaces within your property or the water that you bathe or wash in. There are three types of gas boilers you can choose from:

1. Standard boilers

Standard boilers (also known as regular boilers, conventional boilers or heat-only boilers) use hot water cylinders and water tanks to store and supply your home with hot water and heating via hot water being pumped around your radiators.

These boilers tend to be rather large and require a lot of space, but if your boiler were to break down as a heat source, your system would still be able to provide hot water potentially via an electrical immersion heater located usually within your hot water cylinder.

2. System boiler

A system boiler is slightly different to a standard boiler as the pump for the system and other components are situated inside the boiler itself.

The boiler produces hot water by burning gas and transferring this heat into the primary system water. This is then either pumped around your radiators to heat your home or pumped up to a separate  hot water cylinder where it heats the water you bathe and wash with. They are commonly combined with an unvented hot water cylinder. If you live in a large property, this type of cylinder is excellent for supplying good hot water pressure to multiple taps simultaneously. 

3. Combi boiler

A combi boiler is a single unit with no hot water cylinder or tank. These boilers are great because they are compact if you live somewhere with little space. They are designed to supply hot water on demand.

They are also quick to install, cost-effective and energy-efficient.

Want to find out more about combi boilers?

We've got you covered...

We've got you covered...

Check out everything you need to know about combi boilers, including why they're well suited to your home and how they work.

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The differences between biomass boilers and gas boilers

Now we understand biomass and gas boilers a little better, let's go through the different criteria you need to compare when choosing which one is right for you.

Biomass vs gas boilers: Price

Depending on the boiler type (standard, system or combi), a gas boiler can cost anywhere between £1,500 to £3,500. A good Worcester Bosch combi boiler, for example, costs around £2,000 - a considerably more affordable option than a biomass boiler.

The cost of a biomass boiler can vary greatly depending on the brand, the fuel and the boiler type. These factors could affect the cost of a biomass boiler and make things slightly more affordable. The biggest price point comes from the type of biomass boiler you choose: manual or automatic.

A manual biomass boiler is where you will need to feed your boiler with pellets rather than letting the boiler automatically do this for you. Manual boilers can cost between £4,000 and £10,000, whereas an automatic pellet-feeding boiler can cost as much as £20,000.

Other than boiler type, your fuel choice will also matter. There are three fuel types a biomass boiler can typically use: wood chips, wood logs and wood pellets.

  • Wood chip - Although this fuel type is fairly cheap, it isn't suitable for domestic use. This boiler only works on 60kW, which is insufficient to fuel most households.
  • Wood logs - Wood logs are great for many households. The cost of wood logs can be £100 per tonne and £500 annually. Although wood logs are a good option, you'll need to consider where you'll store them, how you'll keep things clean and how you’ll prepare them since the older the log, the better the fuel.
  • Wood pellets - The most popular fuel type for biomass boilers is wood pellets. They're small and easier to store, easier to transport, lowers carbon emissions and ultimately, costs less.

Biomass boilers are more expensive but since they use renewable energy, there are ways you can make them cheaper. The Renewable Heat Incentive (RHI) helps households fund their biomass boiler by giving them £2,000 and £3,500 a year for seven years. Switching from electricity to biomass, you can save £340 to £650; oil to biomass is £335 to £470, and gas to biomass is £25 to £80 in savings.

Despite the initial upfront costs, biomass boilers have cheaper running costs than gas boilers. Biomass fuel is cheaper per kW than gas as wood can easily be supplied for free. It's also unlikely that you would need to install a brand-new central heating system for your new boiler to function properly. Biomass boilers are a long-term investment.

Biomass vs gas boilers: Installation

Biomass boilers can take some time to install, depending on how big the unit is. Generally speaking, it should take an installer one to two days to fit a biomass boiler into your home. The labour costs are around £200 to £250 a day though this will vary according to who you hire and where you live.

Before installation, you must consider whether the boiler is manual or automatic and where you'll store your materials. Unlike a gas boiler, biomass boilers are more complicated and expensive, which means you must have a registered plumber or professional who can install the boiler for you.

Since biomass boilers are more complex, gas boilers may be what you're after. Most UK homes were built for gas boilers and so all necessary pipework and storage are already installed. Before doing anything, you should consult a Gas Safe registered engineer who can advise you on the best ways to install your boiler.

Biomass vs gas boilers: Space requirements

As briefly mentioned, biomass boilers can be quite large and, therefore, need quite a lot of space.

Somewhere like a garage or outdoor shed can usually accommodate a biomass boiler and helps separate it from your home. Biomass boilers include fuel storage, a tank, an expansion vessel and a chimney that occupy around 10 square metres of space.

If you're struggling for space, you also try using a hand-fed boiler with a hopper. These are smaller (3-5 square metres) but you'll be feeding pellets manually. You also need to consider how each part of your boiler will be able to function. For example, your fuel storage needs to be easy to access so wood deliveries can be made, and your chimney needs to be tall and have nothing to block it.

Gas boilers, on the other hand, come in various sizes.

A standard boiler will require a large amount of space, either in a loft, basement or outside unit, whereas a system boiler will either need a large or medium area. These two boilers, however, can produce plenty of heat for larger properties.

For smaller properties, combi boilers are more compact as they don’t require a storage cylinder or tank, making them perfect for smaller properties and flats but less suitable for larger properties.

Generally speaking, in addition to the dimensions of the actual boiler unit, a boiler should have the following available space:

  • 20 cm above
  • 20 cm below
  • 60 cm surrounding

Biomass vs gas boilers: Maintenance & lifespan

All boilers should be regularly cleaned and inspected, especially during the first year of installation, to make sure that the boiler is running smoothly.

Considering how much ash will be produced from burning biomass, these boilers will need to be cleaned, ideally weekly, to remove all the residue that could block up the system. This requires a lot more effort than a gas boiler, as you'll only need to check for leaks, temperature drops and potential signs of limescale, which can all be done fairly swiftly by a Gas Safe registered engineer.

Although some biomass systems can self-clean, these will cost a lot more. If you're cleaning your system yourself, you must ensure it has all shut down before you can begin.

If your boiler is still under warranty, you must have an annual service check. Otherwise, you risk invalidating your warranty.

Having regular maintenance checks and boiler servicing from a registered engineer can ensure that your boiler is functioning correctly. If properly maintained, the lifespan of a gas boiler could be between 10 to 15 years and 10 to 20 years for a biomass boiler.

Biomass vs gas boilers: Energy efficiency

Biomass boilers have a higher efficiency rating of around 80% to 90% than the standard fossil fuel boiler.

However, with that said, biomass boilers require a lot more upkeep than gas boilers, as you need to supply them with fuel and clean them often.

Although gas boilers are less eco-friendly, they can produce higher temperatures in a short amount of time. Biomass also relies on deliveries and for its fuel to be dry in order to burn. Their unreliability makes them more concerning than gas boilers, which you can depend on no matter the circumstances.

So, what's the verdict… which type of boiler is best for you?

While we have laid out all the necessary information, the decision is ultimately down to you and your situation.

Money is perhaps the biggest factor when it comes to purchasing a boiler. Although biomass boilers are more eco-friendly, the upfront initial costs are much more expensive than a gas boiler.

Biomass boilers  are also not great for those living in small properties. They are a big unit that requires a lot of storage which someone living in a flat may struggle with. In that case, combi boilers would be your best option.

Considering the number of wood pellets and chimney space required, biomass boilers may also be more suitable for those living in rural places. Congested cities may not be able to accommodate a biomass boiler as efficiently.


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