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Last updated: 10th April, 2024


How Much Cheaper is a New Boiler to Run?

How Much Cheaper is a New Boiler to Run?

Key takeaways

  • New boilers are highly efficient, making them amazing at converting energy used into heat for your home.
  • A new boiler could save you over £800 per year on heating bills.
  • Old boilers even if not a combi, can be converted into a modern, highly efficient combi.

New boilers are in fact much cheaper to run than old boilers, this is down to a number of reasons that we will explore in this blog, all you really need to know is upgrading to a new boiler can save you money!

When it comes to home heating, the efficiency of your boiler can have a big impact on your energy bills. An older boiler can be inefficient and costly to run, which can result in higher heating bills each month. 

However, investing in a new, more efficient boiler can offer significant savings over time. In this blog post, we’ll take a closer look at the benefits of upgrading to a new boiler and how much cheaper it can be to run.

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Efficiency Ratings

Before we dive into the specifics of cost savings, it’s important to understand how boilers are rated for efficiency. 

ErP Explained 

ErP stands for Energy-Related Products and is a way of measuring an energy consuming appliance, such as a boiler’s, efficiency in converting the energy it uses into the desired product, heat for your property and its water.

ErP was introduced in 2009 by the European Union in order to increase the clarity of an appliance’s function and aid in the sharing of information from manufacturer to consumer, all the while promoting an eco-consciousness for both.

Energy Labelling

This aspect of ErP is to inform consumers with complete transparency, the energy efficiency of the product they are buying, and its subsequent likelihood of affecting their energy bills.

Appliances are rated in energy efficiency classifications from G to A (A+++ for certain types of appliance); the higher the assigned alphabetical rating, the more efficient the appliance is in terms of its energy usage.

Formerly SEDBUK (Seasonal Efficiency of Domestic Boilers) were responsible for boiler energy ratings, the ErP directive replaced them in the majority of cases for modern appliances.

Some manufacturers still attach a SEDBUK rating to their products, and operate a similar alphabetical classification system.

Naturally, the newer a gas boiler system, the more efficient it is due to engineering and design progression. 

Outdated or failing systems could be the reason for your shock when seeing your monthly energy bills

Most UK boilers are running at 80% energy efficiency with some antiquated models operating at 60% or less! These sub optimal levels of output are as avoidable as they are shocking.

Age of Boiler

Efficiency Percentage

Efficiency Rating

0+ Years

90% +


10+ Years

85% +


15+ Years

80% +


20+ Years

70% +


25+ Years

60% +


The direct correlation between boiler age and its efficiency is clear to see in the newer systems’ ErP, so it may be worth upgrading your model to an energy efficient boiler. check out our handy guide on the most energy efficient boilers.

Combi Boilers

One of the most efficient types of boilers on the market today is the combi boiler. Combi boilers are designed to provide both hot water and central heating in one unit, which means they don’t require a separate hot water cylinder or cold water tank. 

This can make them more compact and easier to install than other types of boilers, but it also means that they can be more efficient.

Combi boilers work by heating water directly from the mains supply, which means that there is no need to store hot water in a tank. 

This can be more efficient than traditional boilers, as there is no heat loss from a hot water tank. In addition, combi boilers are often rated as A or B for energy efficiency, which means that they can be significantly cheaper to run than older boilers.

Is It Worth Changing To A Combi Boiler? - Benefits

Combi boilers offer several advantages over traditional boilers and water storage tanks. Firstly, they are compact and can perform the functions of two appliances, taking up minimal storage space.


In fact, they can fit easily into a standard kitchen cupboard, seamlessly blending in with the decor.

Moreover, combi boilers take their water supply directly from the mains, resulting in a substantial flow pressure that ensures rapid and uninterrupted hot water supply. 

They do not rely on gravity to collect water, which can lead to pooling or slow heating speeds in conventional boilers.

Combi boilers can be remotely controlled by technology such as smart thermostats or smartphone apps, providing convenience and peace of mind to homeowners. 


The water produced by combi boilers is clean and safe to drink, as it has not been stored in a tank for long periods, reducing the likelihood of contamination.


Furthermore, combi boilers are cheap to run as gas, their preferred fuel, is cost-effective and energy-efficient. Most modern combi boilers have been designed to minimise sound output, making them quieter than traditional boilers. 

They are also versatile, as they can run on a variety of fuels and are abundant in terms of 

replacement part availability, ensuring quick and affordable repairs when needed.

Combi Boiler Conversions

Even if your current boiler isn’t a combi and operates on a different system, you can still convert to a sleek and powerful combi.

System, heat only (regular) and back boilers are all capable of being converted into a combi that will both boost your heating and reduce your bills.

Firstly, some due diligence needs to be carried out, combi boilers run off the mains water supply, so you need to ensure the pressure from your cold tap is sufficient. 

The cold tap is the key indicator of a combi’s suitability as often system and regular boilers have pumps on the showers to increase pressure, and if they should be converted into a combi, these pumps would be removed along with the property’s hot water tanks.

Combi conversions which require a full system change will take more time and therefore cost more money up front, but may save you more long term.

Back Boiler Conversions

An old, inefficient back boiler can actually be converted to a combi or system boiler; systems can work out cheaper in terms of the conversion due to a lot of the pipework remaining the same.

However, most people opt for the combi conversion as an upgrading of the entire system could be more efficient in the long run, and may ensure less future faults, reducing repair or maintenance costs.

At iHeat we advise that every installation and conversion is a unique undertaking and time frames are intended only as a guide - for a back boiler conversion carried out by a Gas Safe engineer we recommend you should allow for up to two days of work.

Cost Savings

So, just how much cheaper is a new boiler to run? The exact savings will depend on a number of factors, such as the size of your home, the age of your current boiler, and the fuel type that you use. 

However, in general, you can expect to save around 30% on your heating bills by upgrading to a new, more efficient boiler.

For example, let’s say that you currently have an older boiler with a SEDBUK rating of D. If you upgrade to a new boiler with an A-rated SEDBUK rating, you could save around £300 per year on your heating bills (based on a typical home in the UK). 

Over the lifespan of the boiler, this could add up to thousands of pounds in savings.

In addition to the savings on your heating bills, upgrading to a new boiler can also offer other benefits, such as improved reliability and reduced maintenance costs. 

Newer boilers are often more reliable than older boilers, as they are less likely to break down and require repairs. This can help to reduce the cost of maintenance and repairs over time.

Environmental Benefits

In addition to the cost savings, upgrading to a new, more efficient boiler can also have environmental benefits

Older boilers can be inefficient and produce more carbon emissions than newer boilers. By upgrading to a new boiler, you can help to reduce your carbon footprint and contribute to a more sustainable future.


In summary, upgrading to a new, more efficient boiler can offer significant cost savings over time. By choosing a boiler with a high SEDBUK rating, such as one of our collection manufactured by trusted anc celebrated brands including:

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Frequently Asked Questions

Will a New Boiler Be Cheaper to Run?

Yes, a new boiler will generally be cheaper to run compared to an older model. Modern boilers are designed to be much more energy-efficient, meaning they use less fuel to produce the same amount of heat. This efficiency can lead to significant savings on your energy bills. The exact savings will depend on the age and condition of your old boiler, as well as the specific model and efficiency rating of the new boiler.

How Much Money Will I Save with a New Boiler?

The amount of money you can save with a new boiler depends on several factors, including the efficiency of your old and new boiler, your usage patterns, and current energy prices. On average, replacing an old G-rated boiler with a new A-rated condensing boiler, along with updated heating controls, could save you around £200 to £300 per year on your heating bill, according to the Energy Saving Trust. These savings can vary based on individual circumstances.

How Much Cheaper is a Combi Boiler to Run?

Combi boilers can be cheaper to run than conventional boilers for several reasons:

  • They are generally more efficient because they heat water directly from the mains on demand, meaning there's no need to heat and store a tank of water.
  • This on-demand heating reduces heat loss, making combi boilers more cost-effective, especially in smaller homes with less space for water storage.
  • Savings will vary based on the efficiency of the boiler being replaced and the new combi boiler's efficiency.

Is It Worth Getting a New Boiler Now?

Getting a new boiler can be worth the investment, especially if your current boiler is old, inefficient, or frequently requires repairs. A new boiler can offer better reliability, lower energy bills due to higher efficiency, and peace of mind with new warranties. Additionally, with increasing focus on energy efficiency and potential future regulations on carbon emissions, upgrading to a newer model could be a proactive choice.

Is It Worth Repairing a 20 Year Old Boiler?

While repairing a 20-year-old boiler might be a short-term solution to a problem, it's often not cost-effective in the long run. Older boilers are less efficient and more prone to breakdowns, meaning you could end up spending more on repairs and energy bills than the cost of a new, efficient model. Consider the frequency and cost of recent repairs, and compare these to the benefits of a new boiler.

Should I Replace My 20 Year Old Boiler?

Yes, replacing a 20-year-old boiler is usually advisable. Modern boilers are significantly more efficient and environmentally friendly. A new boiler could not only reduce your heating bills but also lower your home's carbon footprint. Additionally, new boilers come with warranties that can provide peace of mind regarding future repair costs.

How Much More Efficient is a New Boiler Compared to a 20 Year Old One?

A new boiler can be up to 90% or more efficient, whereas a boiler that's 20 years old may only be around 60% to 70% efficient, depending on its condition and maintenance history. This improvement in efficiency can translate to considerable savings on your energy bills and a reduction in greenhouse gas emissions. The actual efficiency gain will depend on the specific models being compared.

Stephen Day profile photo
Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.