Updated: June 13, 2024

When it is time to replace your old boiler, there will be many options for you to choose from. Your final decision will be based on different factors for sure. You will be considering size, output power, type, brand and so on. Another important option which you might be missing, especially if you care about the environment, and that is a green boiler. 

There isn’t a green boiler in the literal sense but there are boilers which have green qualities. And there are boilers which are greener than others. 

What makes a boiler green?

When you replace your old boiler with a greener, more efficient one, you can expect your energy bills to decrease. 

It can be determined that a boiler is greener when it is quite efficient in turning fuel into heat. When this is possible, a boiler will be awarded a high efficiency rating. 

The ErP label can show such details. These ratings start at A++ to G. What is more, space heating efficiency for each boiler will be shown, too, as a percentage.

Which boilers are very green?

Green boilers come in different types and sizes. A green boiler can be a condensing boiler that uses gas, oil or LPG as fuel or an electric or a biomass boiler. While they are not green boilers, they still have green qualities. 

Condensing boilers

Green boilers are much greener than old non-condensing boilers. We can’t call them completely green due to the fact that they burn fossil fuels (gas or oil). 

What makes condensing boilers efficient is something called: Flue Gas Heat Recovery System. This system allows the heat that usually goes out of the flue pipe to be used again to heat your home. 

This feature doesn’t exist in non-condensing boilers. Otherwise, some of the heat produced by non-condensing boilers will just go straight out of the system. As a result, your boiler will burn more fuel to make more energy and compensate for the energy lost. 

Electric boilers

Electric boilers are the closest to being green. Well, to begin with, they don’t burn fossil fuel because they run on electricity. So no carbon is emitted. 

However, they are not completely green unless they take their electricity from a renewable energy source, such as solar panels. So if you want your boiler to have zero emissions, you should connect it to a renewable source of energy.

Biomass boilers

Biomass boilers use wood as fuel, which is carbon neutral. These boilers use pellets, wood chips or logs. All these fuel types are relatively not very expensive. 

You can even earn some payments through the Renewable Heat Incentive. This is a reward for heating homes in an environmentally friendly way. 

Read more: Best combi boilers & boiler brands

eco boiler cost

Why should I get a green boiler?

Well, to put it simply, an efficient boiler uses less fuel and as a result, you will have lower heating bills. So using a boiler with green quality can save you up some money on energy bills. 

What is more, an efficient boiler can reduce your carbon footprint if you are looking for ways to be more environmentally friendly. New boilers require less fuel and waste less energy than old boilers. 

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Why are old boilers not very efficient?

Boilers tend to lose their efficiency over time. Your system will not run as smoothly as it used to as its parts begin to wear out. This can steadily increase your heating bills. 

What is more, leaving your boiler without maintenance or service for a long time can greatly decrease its efficiency. So you might notice a surge in energy bills with an old boiler. 

Generally speaking, your boiler should be replaced every 10 years or so. Boiler efficiency can drop to 85% after 15 years or use and to 70% after 20 years. 

What is the cost of a new boiler?

The price of a new boiler can vary depending on different factors such as: the fuel type, type of boiler, brand,m and output power. 

The installation cost should also be considered. The cost of installation can be different for each job. In some cases, it can be low and in other more complex jobs, that involve different tasks, it can be high. Also, different regions have different prices.

In general, gas condensing boilers are the most affordable due to how common they are across the UK. On the other hand, the most expensive boiler type can be an automatic biomass boiler.

Boiler type Potential Cost (without installation)
Gas Boiler£500 – £3,000
Oil Boiler£1,000 – £3,250
LPG Boiler£1,000 – £3,000
Electric Boiler£900 – £4,000
Biomass Boiler£4,000 – £21,00

What are the renewable alternatives to gas boilers?

There are other options for home heating than just boilers. These include renewable heating systems such as heat pumps and thermal panels. These systems can take heat from a sustainable source and use it to heat your home. 

Heat pumps

A heat pump operates by taking heat from the air outside your home or the underground. There are two types of heat pumps:

Air source heat pumps

Ground source heat pumps

Air source heat pumps 

Air source heat pumps are more affordable than ground source heat pumps. The outdoor unit of an air source heat pump includes a fan. This fan can draw the air inside for the heat pump to capture and heat. And this is how you have a sustainable source of hot water and heating. 

Many models of heat pumps can heat even when the outdoor temperature is as low as -25°C. In short, heat pumps can still work even in winter. 

Ground source heat pumps

On the other hand, ground source heat pumps are more challenging to install. First of all, they need a large outside space. A series of pipes will have to be buried underground. You should rule out the idea of a ground source heat pump if you don’t have enough outdoor space. 

The way these systems work is that a refrigerant liquid goes through the pipes in order to absorb heat from the ground. Temperatures underground are between 10°C and 15°C all year long. This heat then goes back to the heat pump where it can be heated further. 

Heat pumps have a longer lifespan. More than boilers. They can last as long as 20-25 years. They are better suited to well insulated homes. They heat water to a lower temperature than a boiler. 

Solar thermal

Solar thermal panels are another option to consider. They are good for homes with a hot water cylinder. They are not a complete heating system on their own but they can help your boiler. 

These roof panels contain a liquid that can absorb heat. This heat will go through an immersion heater in the hot water cylinder, which can heat the water.

Using the sun’s heat, solar thermal panels can provide between 40% to 70% of your household’s demand for hot water yearly. When it comes to the running costs, there is none. And on top of that, they require little maintenance. 

Read about: Regular Boilers and how does it works

green alternative to gas boiler
green alternative to gas boiler

Switching from gas boilers to renewable heating system: difficulties and challenges

Most UK homes are built in a way to suit gas boilers. So it is normal that switching your system will be met with certain challenges.

Gas boilers heat water to a higher temperature than that of a heat pump. So gas boilers will heat a room easily with a standard radiator. As for heat pumps, they might need a large radiator or underfloor heating. 

Then there’s the installation. Replacing an old gas boiler with a new one is a simple job for a qualified heating engineer. Replacing a boiler with a heat pump is definitely possible but likely to come at a higher price and take more time. This is particularly true of ground source heat pumps as pipes need to be buried underground.

When it comes to installation, replacing your gas boiler with another one is an easy job for a professional installer that can take little time. On the other hand, replacing your gas boiler with a renewable heating system such as a heat pump can be more costly and take more time. This is the case especially with ground source heat pumps due to all the extra work of digging and burying the pipes underground.

As for solar thermal, they aren’t able to fully replace your gas boiler. Instead they work together with your boiler. A solar thermal system can meet your home’s hot water demand by 40% and 70%. Keep in mind that solar thermal systems require a hot water cylinder to store the hot water so they will not be suitable for homes that use a combi boiler. 

Read about: Genuine Vaillant Boilers Review In Uk

Which is the greenest fuel for home heating?

Natural gas is the most popular fuel for home heating in the UK. Around 85% of UK homes use it on a daily basis. Without a doubt, gas isn’t very green after all.

Natural gas is among fossil fuels. So it can increase the level of carbon in the atmosphere. This is also true of oil and LPG as well. These two are the most popular options for homes which are not connected to the national gas network.

If we are to make a list of these types of fuels, it will be like this: oil has the worst carbon footprint. It is followed by natural gas and then electricity. Of course, if your electricity source is a renewable system such as solar panels, then you will have zero carbon emissions.

With the use of condensing technology, we can lessen the effects of fossil fuels. They enable boilers to have green credentials. 

Read about: Professional & Reliable Boiler Repair

How can I improve the efficiency of my heating system?

A new condensing boiler isn’t the only way that can help you make your system more efficient. Here are some other things that you can try:

smart thermostats

Smart thermostats are a game changer as they can grant you control over your home’s heating. They allow you to set the heating inside your home even when you’re out by using your smartphone. 

Smart thermostats can gradually adapt themselves to your heating habits. They will know when to turn themselves on and off. What is more, they also know when your house is empty so they will not heat an empty room. 


To stop the heat from escaping, you would need to insulate your home in order to keep your home warm for a longer time. Places that you can insulate include: the loft, floors, cavity walls. You can also double glaze your windows when replacing single glazed windows around your home. 

Read about: Common Sime Boiler Error Codes

green alternative to gas boiler

Turning off the radiators that you aren’t using

It goes without saying that in order to save money on energy bills, you shouldn’t heat rooms that are empty. 

Use radiator reflectors

A radiator can warm up all the sides. This includes the back side of a radiator. So a lot of heat will be going to the wall behind the radiator. By using radiator reflectors you can bounce back the heat back into the room. As a result, your room will heat up faster and your heating will not be on for so long. 

Bleeding the radiators

When air is trapped in your radiators, they can turn cold. This air can prevent hot water from going through your system so easily. As a result, your rooms will take longer to warm up. Bleeding your radiators can free the air from your system. 

Get a magnetic filter

Limescale and rust can both build up in the pipes over time and cause a blockage. A magnetic filter can attract those debris and stop the blockage from happening. 

Have your boiler serviced annually 

A boiler service is quite important if you want to keep your boiler in top condition. They can also keep your warranty valid as some manufacturers will consider their warranty invalid in case your boiler hasn’t been serviced in quite a while. 

During a boiler service, the heating engineer will inspect your boilers for any problems that might be keeping your boiler from operating as efficiently as possible. Always make sure to hire a Gas Safe Registered engineer. 

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How can I keep my heating system efficient?

There are several things you can do to keep your heating system working efficiently. These include:
smart thermostats
Turning off the radiators that you aren’t using
Use radiator reflectors
Bleeding the radiators
Get a magnetic filter
Have your boiler serviced annually 

What are some alternatives to gas boilers?

Other greener options to gas boilers are:
Air source heat pumps
Ground source heat pumps
Solar thermal

Which fuel is the best to use for a reduced carbon footprint?

If we are to make a list of these types of fuels, it will be like this: oil has the worst carbon footprint. It is followed by natural gas and then electricity. Of course, if your electricity source is a renewable system such as solar panels, then you will have zero carbon emissions.

Why do old boilers lose their efficiency?

Over time, boilers tend to lose their efficiency. Boilers that do not get boiler service and maintenance yearly can also lose their efficiency.