What Is A Green Boiler?

James Elston
Written by James Elston
Updated on 1st December 2023
Posted on 30th November 2023
Topic: Boiler Guides
What Is A Green Boiler

What is a green boiler for central heating?

viessmann vitodens 050-w combi boiler green boiler

A green boiler is as close to an eco-friendly boiler as you can get. Many boilers that are classed as ‘green boilers’ still rely on fossil fuels.

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However, they harness energy in a more environmentally conscious way than traditional non-condensing boilers. Although some of these boilers still burn fuel, they burn fuel more efficiently.

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What kind of fuel does your boiler use?

Video: What is a green boiler?

This video goes through what is a green boiler, what makes a boiler green? And other frequently asked questions.

Changing from an inefficient boiler to a greener boiler can save you up to £580 per year on bills – This could double when energy prices increase on the 1st April 2022.

Not only does investing in an eco boiler help the environment but, given how they conserve energy using specific technology, they’re also far cheaper to run, which saves you money on bills and justifies how much a new boiler cost.

The main eco boiler types are condensing boilers, hydrogen ready boilers, electric, biomass, and 100% hydrogen fuel boilers. This article will examine what makes these green boilers green, what alternatives to gas boilers there are, and the benefits of making your home run on clean energy.

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What kind of fuel does your boiler use?

What makes a green boiler?

green boiler eco friendly

To put it simply, a green boiler is any boiler that can convert the majority of the fuel it burns into heat energy, with minimal wastage. Most of the best combi boilers that are available in the UK are green boilers.

Based on the Energy-related Products (ErP) rating system, an eco boiler should be A-rated which means between 92-94% efficient. Older G-rated gas boilers are only around 60-70% energy efficient, meaning that sometimes as much as 40% of energy is wasted.

To make up for this wasted energy in gas heating systems, more fossil fuels need to be burned. An eco boiler may not be 100% energy efficient, but it is a lot greener than the likes of a traditional old-style gas boiler, as it releases far fewer carbon emissions.

How to tell if a boiler is green or not

You can judge how energy efficient a boiler is by looking at its ErP rating. The ErP system was introduced by the European Union in 2009 in a move to encourage more households to invest in energy-efficient boilers.

This rating system allows consumers to clearly understand how efficient their boiler is. An A-grade rating means that the boiler is at least 92% efficient.

An eco boiler can also be identified by how it appears. To increase efficiency, green system boilers tend to feature just one hot water tank, as opposed to conventional boilers which have two.

You’ll also find the heating system and storage system as close together as possible, whereas before these two were often placed considerably far apart in the household.

Which are the greenest types of boilers?

Electric boilers 

electric boiler green boiler

Electric boilers can be the most energy-efficient boilers available, as long as your house runs on renewable electricity.

If your house is not supplied by a renewable energy provider or source, electric heating cannot be considered 100% eco-friendly, as fossil fuels are still required to create the electricity used to run the machine.

However, electric boilers are still a greener alternative to traditional gas boilers, as they run on electricity and are not as reliant on fossil fuels.

To make your electric boiler 100% eco-friendly, you would have to switch to a renewable electricity provider such as OVO, or use solely solar, wind, hydro, or another renewable energy source.

Biomass boilers 

Biomass boilers are carbon-neutral, meaning they don’t rely on fossil fuels to produce heat. Instead, a biomass system burns logs, wood, and chips to produce the heat energy required. Burning wood emits less CO2 than it does through natural decay, as the carbon has been effectively absorbed by the tree.

Wood is one of the cheapest fuel sources available and biomass heating systems are also a great solution for off-grid locations. To ensure that your biomass boiler is 100% green, you should ensure that your wood source is sustainable and trees are replanted to replace what you have used.

worcester bosch 4000 hydrogen ready boiler

Hydrogen ready boilers

A hydrogen ready boiler can work as a gas combi boiler by burning natural gas, however, this is not exactly the greenest way to heat your home. Luckily, these hydrogen boilers can also run on 100% pure hydrogen.

This is considered to be a green solution as the only byproduct of burning hydrogen is vapour water; this type of boiler produces zero carbon emissions.

Hydrogen ready boilers are one of the newer forms of green boilers, so research is still ongoing into their environmental impact.

Most new condensing boilers are being made to be hydrogen ready up to 20%, meaning they can be modified to run on 100% hydrogen once there is a switch in fuel source in the UK. If you are looking for boiler installation in the future ensure that your new boiler is hydrogen ready.

Leading boiler manufacturers such as Worcester Bosch and Viessmann are investing a lot into the development of hydrogen boilers, as they believe them to be a key component of greener home heating systems of the future.

Condensing boilers 

Condensing boilers are boilers that are fueled by either gas or oil but have condensing technology inside. This technology ensures that as much gas is recirculated and burnt during the heating process.

ideal logic combi boiler

Given the reliance of this boiler type on fossil fuels and the fact that it emits carbon dioxide, it cannot be considered 100% environmentally friendly. However, it is far greener than non-condensing boilers.

A condensing boiler is considered to have green qualities due to the fact it can re-use some of the heat that would otherwise be wasted. A condensing boiler features a Flue Gas Heat Recovery System, which uses heat exchanges to retain energy and return it to the main heat exchanger.

If it wasn’t for the FGHRS, over a quarter of your energy would be lost through the flue pipe. Condensing combi boilers can ensure around 90% energy efficiency, making them a grade B boiler based on their ErP rating.

Green alternatives to gas boilers

To make your central heating system greener, you may have to change a lot more than just your boiler. Although gas central heating systems is where a lot of household carbon emissions come from, the whole framework of your heating system could be responsible for heat loss and energy wastage.

To ensure that your entire home is combating climate change, consider investing in the following alternatives to gas boilers:

solar panels

Solar thermal panels 

Solar thermal panels can assist your boiler by providing hot water that has been heated directly by the sun. Although this hot water cannot be relied on entirely (producing between 40-70% of your annual hot water requirements), solar thermal panels do take the strain off your boiler, reducing your carbon footprint.

Solar panels are low maintenance as they don’t require a lot of upkeep once they are fitted. However, they do require plenty of sunshine to work.

Heat pumps

There are two types of heat pumps available: ground source heat pumps and air source heat pumps. A heat pump works by absorbing the air from either the ground or the air and converting it into heat for your home.

ground source heat pump

Ground source heat pump

A ground source heat pump is placed around 1.2m below the surface of the earth in your garden. It consists of a series of pipes that collects low-temperature solar energy that gets trapped underground. This solar energy is then compressed to reach a higher temperature which is suitable for heating your home. A ground source heat pump is far more expensive than an air pump.

Air source heat pump

An air source heat pump, on the other hand, is cheaper to install, given that its functions take place entirely above ground. The air source heat pump consists of a fan that draws in air from outside, which it then compresses and turns into useable home heat.

Heat pumps work best in insulated homes featuring other eco heating systems such as underfloor heating. The cost of an air source heat pump is also expensive when compared to a hydrogen-ready boiler. Expect costs of around £5,000 at least.

A ground source heat pump cost even more to install. If you have the space and capacity for a ground source heat pump then you can expect costs to be around £15,000. This can pretty much settle the air source vs ground source heat pump debate for most people as not many people will want to pay the large costs involved.

Why you need a green boiler

You will need to switch to an eco-friendly boiler eventually as boilers are eventually going to be phased out. Currently, around 80% of UK homes are heated using gas boilers.

Considering that around a quarter of the country’s entire carbon emissions comes from households, it’s understandable why the government is beginning to phase out the use of gas central heating.

piggy bank

Although there is no law, as of yet, which says that you should not heat your home using a gas boiler, the government’s Heating and Building Strategy states that the installation of new gas boilers will be banned by 2025 in new homes and that gas boilers will no longer be for sale by the year 2035.

As this strategy progresses, it will become increasingly difficult to get your gas boiler repaired, and with no new gas boilers available to buy, it would make the most sense to invest in a new eco boiler.

The sooner you decarbonise, the sooner you can make your home ready for a greener future, while also benefiting from a cheaper heating system!

What are the benefits of upgrading your gas boiler?

Upgrading your boiler to a greener one may seem like an unnecessary investment if your current gas boiler is working fine. However, not only will an eco boiler last longer, but it will also help to reduce your carbon footprint and save you money on the energy bills.

They last longer


Typical gas boilers tend to be replaced every 15 years, which is a relatively short lifespan compared to green boilers, which use energy more efficiently and don’t get worn out as easily.

A biomass boiler can last up to 20 years, while an electric boiler can last up to 25 years!

Reduced carbon emissions

We encourage you to find a gas boiler alternative to help reach the 2050 net-zero target. To reach this target, the Energy Saving Trust state that we have to cut our emissions by 95%. The best way to do this would be to switch to a greener boiler. You can reduce your carbon footprint massively by simply investing in a green boiler.

Saves money on your heating bills

Greener boilers are more energy-efficient, meaning that they use most of the energy they produce. With minimal heat wasted, you could save a lot on your heating bill. If you still use a G-rated boiler, by switching to a green A-rated boiler, you could save £580 per year on your heating bill, according to the Energy Saving Trust.

What is the cost of a new boiler?

Boiler Central offers all green boiler types for great prices, from electric to hydrogen ready boilers. To give you an idea of how much a new boiler will cost you, Boiler Central’s electric boiler price range ranges from as little as £600 to £3,000 for more advanced models.

If you’re looking for hydrogen-ready combi boilers, then Boiler Central has a great range starting from around £1,800 including full installation and 12 years warranty. Check out the best combi boiler available right now from our shortlist:

For condensing boilers, prices start at £800 for an AlphaCombi E-TEC Plus not including installation.

What are the challenges of transitioning from gas to renewable energy?

When it comes to switching from a gas to a greener boiler, several challenges must first be considered.

The main challenge is the fact that most houses in the UK have been built to support a gas heating system. Gas has a higher heat output, meaning homes need less insulation. Therefore, homeowners may need to invest in more insulation to support a greener boiler.

Another challenge is the cost associated with installing a new eco boiler, as well as the cost of fitting insulation and heating pumps. Certain models, particularly new electric and hydrogen ready models, can be expensive. However, the plus side of this is the amount of money you’ll save on heating bills in the long term.


Which are the most energy-efficient boilers?


Hydrogen-ready and electric heating systems are amongst the most energy-efficient, and most contemporary models are classed as being grade-A according to the ErP rating system. They can be made more energy-efficient through the use of sustainable electricity and hydrogen sources.

Are gas boilers being phased out in the UK?

Boilers that run on gas are slowly being phased out in the UK, and after 2025, no new build home will be fitted with a 100% natural gas boiler they must be hydrogen ready. If you are unsure what this means for you, check out our heat pump vs boiler page to see which is the best option for you.

price tag

However, nothing is stopping you from continuing to use your old boiler, however, the government are making an effort to slowly phase gas-based boilers out. There are several schemes made to encourage gas users to make the switch, such as the Boiler Upgrade Scheme and the Renewable Heat Incentive scheme.

How much are eco-friendly boilers?

The price of eco-friendly boilers ranges greatly depending on the type you wish to invest in. Boiler Central sells a range of green boilers, with the average starting price for a new gas boiler being around £1,600.

How much money can I save by installing a greener boiler?

By switching to a greener boiler, you could save upwards of £300 per year on heating bills.

Eco-friendly green boiler conclusion

Switching to an environmentally-friendly boiler, supplied by Boiler Central, could save you a considerable amount and also help set your house up for a greener future. You can get a boiler quote online now in under 20 seconds.

By opting for an electric, hydrogen, condensing, or biomass heating system, and fitting your house with the likes of infrared heating panels, you will officially be doing your bit to prevent climate change. All in all, it really does depend on your personal preference.

Written by
James Elston
James Elston Director Of Boiler Central
Posted on: 30th November 2023
Topic: Boiler Guides

James Elston is our resident boiler replacement and heating expert here at Boiler Central. With over 20 years experience in the boiler installation industry, James ensures that he knows everything there is about our Gas Safe boiler installations, energy saving and home heating solutions. This can be from simply procuring the latest best combi boilers, to reviewing and ensuring that Boiler Central maintains the highest standards across our boiler installation company.

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