Biomass boilers vs conventional gas boilers

Comparing the cost of biomass boilers with conventional boilers

Biomass boilers start at about £7,000 for a 12kW domestic version, which is sufficient to provide heat and hot water for a 4-bed house. A comparably sized gas boiler will only cost around £2500 to install. A bigger biomass boiler with an auto-feed hopper may cost closer to £12,000.

However, biomass boilers burn biomass fuel, which is considered renewable. Therefore, provided that the boiler is MCS-accredited, you will be eligible for the Renewable Heat Incentive that will pay you for every kilowatt-hour of heat produced.

In terms of the cost of fuel, the average price of wood pellets are around 4.2p/kWh which is very much in line with mains gas, while oil costs a little more at 6p/kWh. However, the price of wood pellets is likely to become more attractive going forward since gas prices have continued to rise in recent years, and this trend looks to continue. Biomass boilers are completely independent of the fluctuating import prices of foreign fuels such as gas and oil.

Also, if you are lucky enough to have a free supply of wood, then you can heat your home at zero cost.

Comparing the efficiency of biomass boilers with conventional boilers

Biomass boilers run at an efficiency of 89 – 91% (Trianco Greenflame – 91%; Angus Orlingo 500 – 92%), while the top-rated gas boilers similarly run between 88 – 91% efficiency (Baxi Duo-tec HEA 91%; Valiant Ecotec Plus series over 91%); therefore biomass boilers are comparable to conventional gas boilers.

Comparing biomass boiler maintenance with conventional boilers

If you decide to opt for a biomass boiler, you will have to feed it fuel from time to time. For example the Baxi Bioflo will need to be refuelled every 3 -4 days. Bigger biomass boilers with auto-feed hoppers will only need to be refuelled every couple of weeks. In addition, ash builds up as part of the combustion process (wood combustion produces about 0.5% – 1.5% by weight of ash) which will need to be emptied too.

A gas boiler is very much an ‘install and forget’ technology, so it is the clear winner here.

Comparing the size of biomass with conventional boilers

Biomass boilers are much bigger than conventional boilers, since they will have to have some element of an auto-feed option. In the case of the Baxi Bioflo, it is 1.2m high, while a conventional gas boiler is half the size.

The other thing is that gas tends to come from the mains gas supply via a gas pipe. A biomass boiler will need to be situated relatively close to a fuel supply, which obviously means you are going to need a decent-sized storage facility that can be kept dry and contained so there is no fire risk.

Comparing the environmental credentials of biomass boilers and conventional boilers

Biomass boilers run on biomass fuel. Biomass fuel tends to be derived from quick-growing trees and fuel grasses. Trees absorb carbon dioxide as part of photosynthesis, which is the process that allows them to produce sugars required for growth. When the trees are felled and then burnt, they release the same level of carbon dioxide that they took in, meaning that biomass is arguably a carbon-neutral fuel.

It can be argued that gas is also derived from the breakdown of vegetation, but this process takes millions of years, and we are currently using the gas at such a rate that we are getting through our supplies much quicker than it is being replenished; it is therefore not sustainable. As a result gas and other fossil fuels are not considered to be renewable, since the time scale for the process to occur is simply too long.

As a result, burning biomass is not considered particularly harmful to the environment, whereas burning gas is considered to have negative consequences.

The other thing to bear in mind is that growing crops for fuel is only okay if the land that the crops are being grown on has not historically been used to grow food. Growing fuel crops at the expense of food crops is obviously an unsustainable practise.

The final verdict – biomass versus conventional boilers

MCS-approved pellet fired or gasification biomass boilers are comparable with the most efficient conventional gas boilers and, through the Renewable Heat Incentive, they actually produce a very healthy return (provided the heat demand on your EPC is sufficient). Therefore provided you have the space to house the fuel and the boiler itself and you are happy that you are going to have to ‘feed and clean’ the boiler on a regular basis, then a biomass boiler is certainly worth considering.

Obviously they are very expensive to buy upfront, so this too is something you have to bear in mind. If you have access to cheap finance then installing a biomass boiler could actually be a no-brainer!


    • Biomass boilers are more efficient than conventional gas boilers
    • Since they use renewable fuel, the benefit from the Renewable Heat Incentive


    • Biomass boilers require maintenance – they need to be feed fuel and cleared of ash on a regular basis.
    • They require a greater amount of room since the units are not only bigger, you also need to store the fuel somewhere close to the boiler.


    • A biomass boiler might cost £7000, while a gas boiler might cost just £2500.

Installing a biomass boiler?

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