Green Boilers: Best green boilers (and best alternatives) in 2024

Green boilers, or, so-called 'eco-friendly' boilers aren’t just better for the environment, but they can also help you save money on your heating bills, too. 

But what constitutes a green boiler exactly? Can you ever really own a boiler that burns a fossil fuel like natural gas and still be green? 

The reality is that it would be difficult to find anyone willing to define a gas boiler as green, however, with that said there are certainly “greener” options.

That includes modern condensing boilers and even hydrogen-ready models that can accept zero-carbon emitting hydrogen gas.

In this guide, we will help you determine which boilers are greenest, so you can be sure the new boiler you install into your home will be better for the environment and your finances. 

PS. We fit hybrid heat pumps with installation nationwide. Simply answer these questions, get your fixed price and you could get it installed as quick as tomorrow.

What makes a boiler green?

...What exactly makes one boiler greener than the next? 

In the simplest terms, a boiler that is greener is one that can convert more of the fuel it burns into heat energy. This is known as a boiler’s efficiency. 

This means that a boiler with 92% efficiency will use 92% of the energy to generate heat, while 8% will be wasted. This wasted energy or heat is mostly emitted via exhaust fumes.

This essentially means that an inefficient boiler will waste more fuel and demand more fuel to achieve the same amount of hot water as modern efficient models. 

It all means they will emit more carbon, major greenhouse gas and so will be more harmful to the environment. 

Boiler efficiency can be determined by referring to the boiler model’s Energy Related Products Directive or ErP rating. 

What is ErP? 

In 2009, the European Union introduced the Energy Related Products Directive (ErP) in a bid to increase the transparency between manufacturers and consumers, encouraging both parties to favour more environmentally friendly products.

The ErP labelling system applies to both domestic and commercial heating products, including gas boilers. 

Which Boilers are the Greenest? 

There are a variety of different types of boilers that run on various fuels, including condensing gas boilers, electric boilers, and biomass boilers. 

While none of these types of boilers is 100% green boilers, they do have green features and so are worth considering.

Here are the options...

#1 - Condensing Boilers 

While condensing boilers are not green, they are much greener than the older, non-condensing variety. 

The reason condensing gas boilers are not green is that they burn natural gas, which will always emit some level of carbon dioxide, which is a major greenhouse gas that contributes to climate change.

In old non-condensing boilers, hot waste flue gases were released outside of the home, which itself wasted a substantial amount of heat, cost more to run and emitted more carbon. 

Modern condensing boilers are fitted with a Flue Gas Heat Recovery System that makes them recycle/recover the heat from the flue gases, either via a secondary heat exchanger placed before the flue exit, or optimising flow and return temperatures in the main heat exchanger to allow flue gases to hit cooler pipework and transfer energy.

Put simply, this means they produce more heat from the energy they burn and waste less energy during the process.

In fact, by trading in your old boiler for a modern condensing boiler you could save as much as 1,220 kg of CO2 each year.

#2 - Electric Boilers 

Electric boilers i.e., boilers that are powered by electricity are often considered 100% green since the energy they use is converted directly to heat and produces zero emissions. 

Many electric combi boilers currently available have achieved 100% efficiency ratings. This means that the energy used is converted directly to heat and is not lost, unlike gas boilers, where some of the heat can be lost via exhaust fumes.

While it’s true that there are renewable forms of electricity generation e.g., solar and wind, the reality is that at present a large majority of electricity generation in the UK still relies on fossil fuels. 

#3 - Biomass Boilers 

Biomass boilers use biomass fuels such as wood from trees, logs and chips and so is considered a carbon-neutral practice. 

This is because the only carbon it releases is the carbon the tree absorbs during its lifespan. However, in order for it to remain a carbon-neutral process, new trees have to be planted.

In an ideal world, we would plant twice as many trees as we cut down if not more, to reverse some of the damaging effects deforestation has had on our planet. Burning wood and not replanting enough trees to replace them is unsustainable.

In addition, biomass boilers are typically expensive to buy and install, but you may be able to benefit from the Renewable Heat Incentive. 

#4 - Hydrogen Ready Boilers 

A hydrogen boiler is very similar to an everyday gas combi boiler, only instead of using natural gas as fuel, it uses hydrogen gas. 

100% hydrogen boilers are green since the burning of hydrogen only produces water vapour and has zero carbon output. For this reason, they are under serious consideration by the UK government and there are many trial projects currently underway.

However, just like electricity generation, for the moment hydrogen generation isn’t entirely green and does result in the emission of carbon. Thankfully, there are research projects trying to find a way to make the process more efficient and entirely carbon-free. 

The major benefit of hydrogen boilers is that they can potentially use the existing gas network, which will make adoption quicker, cheaper, and easier to roll out nationwide. 

For many, the argument has always been that it’s far easier to adopt a new green fuel rather than adopt a new type of heating system. 

Read our comprehensive guide on hydrogen boilers. 

 Why do you need a Green Boiler? 

At present, domestic heating is responsible for around 15% of the UK’s carbon emissions, which is in direct conflict with the UK government’s carbon-neutral goals of 2050.

So not only does adopting a low carbon or zero-carbon alternative mean you are doing your bit for the environment, but in the coming years, it’s likely that we will see more aggressive legislation to compel households to make the switch to greener home heating. 

How can upgrading your boiler help? 

For now, although not entirely green, upgrading an old boiler can also help you reduce your carbon emissions and save money on your heating bills. 

Firstly, they can help you save energy (and money!) 

According to the Energy Saving Trust by replacing your old G-rated non-condensing boiler with a modern A-rated condensing boiler you could save as much as £300 a year.

Paired together with a smart thermostat and thermostatic radiator valves you could save even more. By installing a Nest, you could save up to £75 and 330kg of carbon a year, thanks to its adaptable learning schedule.

Plus, they reduce your carbon footprint.

Modern A-rated condensing boilers have a considerably lower carbon output than old non-condensing boilers. In fact, by trading your old boiler in for a modern condensing boiler you could save up to 1,220 kg of CO2 per year.

How much does a new boiler cost? 

Boiler installation costs can vary significantly, which is dependent on numerous factors, these can be summarised as follows: 

• The type of boiler you have installed e.g. combi or system

• The model you choose e.g. mid-range vs. premium

• If you want to move your boiler to a different location

• If you want to convert from one boiler type to another

• Any extras you purchase e.g. smart thermostats, filters etc

For illustration, a straightforward combi swap (installing a new combi boiler in place of your current one) is going to be less expensive than converting from a different type of boiler to another e.g. from a combi to a system boiler.

This is due to conversions being more complex to install, taking more time, and requiring more labour and more materials. More everything.

The condensing boiler model you choose also has an impact on the cost and at Heatable we offer more value-orientated brands such as Alpha, as well as award-winning, premium brands such as Worcester Bosch and Viessmann.

Low Carbon Alternatives to Gas Boilers 

A gas boiler or any type of boiler for that matter isn’t your only option when it comes to heating your home and there are in fact many low carbon alternatives available. 

Like gas boilers, none of them is perfect and there are several caveats to be aware of before making any final decisions. Common examples include heat pumps and solar energy. 

Let’s take a closer look…. 

Heat Pumps

The Committee on Climate Change has said that 19 million heat pumps will need to be installed to meet the commitment to reach net zero by 2050. So, they are going to play a big part in the decarbonisation of heating in the UK. 

There are three main types of heat pumps: air source, ground source and hybrid.

They work by absorbing heat from the air, ground or water and can provide both central heating and hot water, while hybrid heat pumps can use a boiler to provide additional heat when the weather is exceptionally cold.

Heat pumps do require small amounts of electricity to operate and combined with the fact that they take the heat from the environment, they are incredibly efficient.

Unfortunately, heat pumps cannot provide the same, consistent heat output as gas boilers, so are unsuitable for many applications.

For example, they are typically installed together with an underfloor heating system and only in modern energy-efficient properties that are very well insulated. 

Heat pumps are also extremely costly to install and ground source models require adequate space to install. Therefore, there are some major barriers to their adoption.

Learn all about hybrid heat pump/boilers in our video tutorial below: 

Solar Thermal Heating Panels 

Solar thermal panels use the sun's radiation to heat water to supply your central heating system and water outlets e.g. taps and showers. They differ from solar PV, which uses the sun’s rays to generate electricity, but PV solar can also be used to provide heating e.g. by powering an immersion heater. 

By harnessing the free power of the sun, you are able to supplement your current heating system and reduce your carbon footprint and energy bills. 

Solar panels can offer heating during daylight hours but are not going to be a reliable source if you are not home until the evening. Currently, solar electric storage is expensive and so not feasible for most households.

Regardless of the costs, solar will rarely provide enough energy to supply a consistent and reliable source of hot water and so is currently only used to supplement a primary heat source.

The Challenges of Renewables 

As can be seen, the transition from gas boilers to modern, low-carbon alternatives isn’t always as straightforward as the media headlines would have you believe. 

There remain several barriers to the adoption of low-carbon heat and a recent report by the EAC found that it will take over 700 years for the UK to make the transition at its current speed.

Differences in heat output 

The first challenge is the major differences in heat outputs between gas boilers and low-carbon alternatives, combined with the thermal efficiency of UK homes. 

For example, a gas boiler can take hot water to extremely high temperatures within a relatively small amount of time and radiate that heat to homes using standard radiators. 

Heat pumps cannot reach such high-temperature levels and are commonly unable to be used with standard radiators. For this reason, it’s often not practical to install them without the necessary home upgrades being made e.g., the installation of larger radiators and thorough insulation.

The cost of installing renewables 

Gas boilers are by no means cheap, but the cost of renewables like heat pumps can be astronomical and well out of financial reach for most households. 

In fact, the Committee on Climate Change has estimated that it would cost an average of £26,000 to switch each UK home to a low-carbon heating system.

The question of cost for systems like ground source heat pumps is not just financial either, they require an adequate amount of space around the property and their installation is notoriously disruptive and lengthy. This often makes them impractical for anything except new build properties. 

Hydrogen - the future of home heating in the UK? 

One potential solution to these barriers is hydrogen fuel, which takes advantage of the current gas infrastructure, which is connected to 8 in 10 homes in the UK.

Therefore, many industry commentators assert that it’s much more practical to change the fuel instead of the heating system in every home.

When burned hydrogen gas emits no carbon, only water vapour and so a 100% hydrogen boiler could be considered a truly green boiler. 

Hydrogen boilers are not yet available to buy, but industry-leading boiler manufacturers like Worcester Bosch and Viessmann are working on prototypes. 

Like electricity production, there remain potential barriers to the clean generation of hydrogen, but there are many research projects underway that are aiming to rectify this.

Get Quotes for a Greener Boiler 

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