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What Is a Condensing Boiler? | Efficient Boilers | Combi Heating

wet central heating system and electric boiler

Have you ever wondered how to heat your home more efficiently while reducing energy bills and carbon emissions? Look no further: condensing boilers are the answer. These innovative heating systems offer unparalleled energy efficiency, making them an excellent choice for environmentally conscious homeowners. Keep reading to discover what makes condensing boilers stand out, how they work, and how to choose the perfect one for your needs.

Key Takeaways

  • Modern Condensing boilers are an energy-efficient and eco-friendly way to heat your home, providing up to 90% efficiency and cost savings.
  • Professional installation by a Gas-safe registered engineer is essential for the safety and longevity of the boiler.
  • Consult with MML Plumbgin when selecting a condensing boiler suitable for your needs to maximize efficiency, reduce carbon emissions, and save on costs & bills.

How does a condensing boiler work?

Condensing boilers are engineered with the aim of maximizing energy efficiency, leveraging the heat from waste gases. They accomplish this through a process called condensation, which involves the transformation of water vapour in the flue gases into liquid form during heat recovery in the heat exchanger. This is how condensing boilers work, unlike non-condensing boilers, which release this valuable heat into the atmosphere, resulting in higher efficiency and lower energy bills.

Condensing boilers primarily consist of:

  • Primary heat exchanger: captures most of the heat generated during the fuel-burning process
  • Secondary heat exchanger: recovers additional heat from the waste gases
  • Condensate pipe: safely disposes of the condensate water produced during the process

The efficient heat recovery system enables condensing boilers to achieve efficiency levels surpassing 90%, a marked improvement over traditional models.

Condensing boilers vs. non-condensing boilers

The efficiency of boilers is the most striking difference when comparing condensing and non-condensing models. Condensing boilers can reach over 90% energy efficiency, while non-condensing boilers typically hover around 70%. This higher efficiency is due to the flue gas recovery system in condensing boilers, which captures more heat during the fuel-burning process.

Aside from their energy efficiency, condensing boilers also offer environmental benefits. By using less fuel and capturing more heat, they produce less carbon emissions than non-condensing boilers. This makes gas condensing boilers an eco-friendly choice for home heating, and an excellent way to reduce your carbon footprint while saving money on your gas bills.

What is a condensing boiler? A smart, efficient way to heat your home!

As an innovative solution for home heating, condensing boilers offer noteworthy energy efficiency and environmental benefits.

These condensing boilers require:

  • Use either gas or oil as their fuel source
  • Employ a flue gas recovery system, which includes a secondary heat exchanger to maximize their efficiency
  • Can achieve over 90% energy efficiency, significantly higher than conventional boilers

One popular type of condensing boiler is the combination boiler, also known as a combi boiler. These modern boilers provide both hot water and heating without the need for a separate tank, making them an ideal choice for small to medium-sized homes. With their high efficiency and eco-friendly features, modern condensing boilers are a smart, efficient way to heat your home while reducing your carbon footprint.

How Do I Know If I Have a Condensing Boiler?

Identifying a condensing boiler model involves searching for a white plastic 22mm ‘condensate pipe’ and monitoring for steam emanating from the boiler flue.

If your current boiler is over 10 years old or you’re unsure whether it’s a condensing model, you might want to consider upgrading to a modern condensing boiler by MML Plumbing for improved energy efficiency and potential savings of up to £300 a year.

Advantages of condensing boilers

Compared to traditional non-condensing boilers, condensing boilers provide a host of advantages. First and foremost, their energy efficiency is substantially higher, with some models achieving over 90% efficiency. This increased efficiency is due to the flue gas recovery system in condensing boilers, which captures more heat from the fuel-burning process and recovers useful heat from the flue gases.

In addition to their energy efficiency, condensing boilers also provide significant environmental benefits. Installing one in your home can lead to a reduction of up to 1,200 kg of carbon emissions per year. This means that by choosing a condensing boiler, you’re not only saving money on your bills but also contributing to a greener planet.

Combi boiler with heating and hot water

What are the disadvantages of a condensing boiler?

Despite the many benefits of condensing boilers, they also come with some potential drawbacks. One issue that can arise is the freezing of the condensate pipe, which carries acidic water produced during the condensing process to a drain. If this pipe freezes, it can cause a blockage and prevent the boiler from functioning properly. However, this issue can be easily prevented by properly insulating the condensate pipe and seeking professional advice if you’re unsure about thawing it.

Additionally, the initial installation costs of a condensing boiler may be higher than those of a regular boiler, but the long-term energy savings should more than offset this expense.

Condensing Boiler Installation Diagram

Combi boiler diagram

An installation diagram for a condensing boiler visually presents the components and connections involved in the setup process. This diagram can help you understand how the boiler works and how it is connected to your home’s heating system. It typically includes elements such as the primary and secondary heat exchangers, the flue gas recovery and central heating system itself, and the condensate pipe.

By examining this diagram, you can gain a better understanding of the technology behind condensing boilers and how they provide efficient heating for your home.

Does a condensing boiler need a drain point?

Efficient and safe disposal of condensate water necessitates a drain point in a condensing boiler. This acidic water is produced during the condensing process and must be drained away to prevent damage to the boiler and its components.

The condensing boiler drain point is typically a pipe connected to the boiler, which safely discharges the condensate water into a drain or soakaway. Proper installation and maintenance of the drain point are crucial to the safe operation of your condensing boiler.

Is a condensing boiler the same as a combi boiler?

Even though condensing boilers and combi boilers are frequently referred to together, they perform distinct functions. A condensing boiler is a type of boiler that utilizes condensing technology to capture and reuse heat from waste gases, making it more efficient than non-condensing boilers. On the other hand, a combi boiler is an all-in-one unit that provides both heating and hot water without the need for a separate tank.

While both types of boilers are efficient and environmentally friendly, their main distinction lies in their functions. A condensing boiler focuses on capturing and reusing heat to provide more efficient heating, while a combi boiler is designed to take heat input and supply hot water on demand for a mid-size property.

What’s the Difference Between Condensing Boilers and Combi Boilers?

Despite both condensing and combi boilers being modern and efficient heating solutions, they possess key differences. As previously mentioned, condensing boilers utilize heat recovery systems to capture and reuse waste gases, resulting in higher efficiency levels than non-condensing boilers.

In contrast to oil boilers, combi boilers provide hot water on demand without the need for a separate tank. A combi boiler (combination boiler) is also a condensing boiler, it is just the name of the gas boiler type! Both types of boilers offer several shared benefits, such as energy efficiency, reduced carbon emissions, and cost savings.

Reduce your energy bills with a combi boiler

An upgrade of new gas boilers to a combi boiler can lead to a reduction in energy bills and an improvement in the central heating system’s efficiency. Combi boilers are designed to be more efficient than traditional domestic boilers, using lower flow temperatures to save up to 35% on gas bills.

Additionally, they heat water on demand, making them an energy-efficient and cost-effective option for providing hot water to your home. If you’re looking to lower your energy expenses and reduce your carbon footprint, a combi boiler could be the ideal choice for your home.

Need a new boiler?

Choosing a new boiler entails considering factors like property size, type of boiler burns fuel used, efficiency rating, and cost.

It’s also essential to hire a Gas Safe registered engineer company like MML Plumbing for the installation and maintenance of your new boiler to ensure your safety and the boiler’s longevity.

What temperature should a condensing boiler be set at?

For optimal efficiency and performance, the central heating temperature of your condensing boiler should be around 70°C and the hot water temperature around 60°C. This temperature setting allows the boiler to operate in its most efficient condensing mode while providing sufficient heat for your home.

How Much Condensate Water Does a Condensing Boiler Produce?

modern condensing boilers are the future investments

According to the Heating & Hot Water Industry Council (HHIC), an efficient condensing boiler typically generates about two litres of condensate water per hour. This condensate water is a byproduct of the condensing process and must be safely disposed of to keep heat insulation and prevent damage to the combi boiler and its components.

Generally, the condensate water is discharged into a drain or soakaway, ensuring proper disposal and maintenance of your condensing boiler.

Reduce Carbon Emissions

The capacity to reduce carbon emissions is one of the primary benefits of condensing boilers. By utilizing less fuel and capturing more heat, they produce fewer carbon emissions than non-condensing boilers. Installing a condensing boiler in your home can lead to a reduction of up to 1,200 kg of carbon emissions per year.

By choosing a condensing boiler, you’re not only saving money on your energy bills but also contributing to a greener planet.

Condensing boilers have higher efficiency

Condensing boiler installation by our engineers

As previously stated, condensing boilers are highly efficient, achieving efficiency levels exceeding 90%. This is significantly higher than the efficiency of non-condensing boilers, which typically only achieve efficiency levels of around 70%.

The increased efficiency of condensing boilers is due to their heat recovery system, which captures more heat during the fuel-burning process and recovers useful heat from the flue gases. This higher efficiency translates to lower energy consumption, reduced carbon emissions, and cost savings on your energy bills.

Condensing boiler efficiency rating

An efficiency rating quantifies a boiler’s ability to convert energy into useful heat, usually expressed as a percentage. Boilers with higher ratings are more efficient and consume less fuel, resulting in lower energy bills and reduced carbon emissions.

When selecting a condensing boiler like a Worcester or Vaillant, it’s essential to consider its efficiency rating, as this will directly impact its performance and the cost savings you’ll experience. By choosing the advantages of a condensing boiler with a high-efficiency rating, you’re investing in a heating system that will save you money and reduce your carbon footprint in the long run.

How to Choose Between a Combi, System and Regular Boiler?

Choosing the correct boiler type for your home takes into account factors like property size, heating and hot water demand, and space available for installation.

Combi boilers are ideal for small to medium-sized households and provide instant hot water without the need for a separate tank.

System boilers are suitable for small, medium, and large households with a high demand for heating and hot water, but they require a hot water cylinder for storage.

Regular boilers, also known as heat-only boilers, need a considerable amount of space to store a hot water cylinder and a cold water tank in the loft.

When choosing between a combi, a system boiler, or a regular boiler, it’s important to weigh the pros and cons of each type about your specific needs. Consulting our company can help you determine the most suitable boiler for your home, ensuring optimal performance and energy efficiency.

Are condensing boilers safe and reliable?

Condensing boilers are known for their safety and reliability. All components are of the same quality as standard boilers, and in some cases, even higher. They maintain full efficiency throughout operation, ensuring optimal performance and energy savings.

However, to guarantee their safety and longevity, it’s crucial to have them serviced annually by a qualified gas-safe engineer. Regular servicing helps prevent potential issues and ensures that your condensing gas boiler continues to function efficiently and safely.

How long do condensing boilers last?

Generally, the life expectancy of condensing boilers spans 10 to 15 years. To ensure their longevity and optimal central heating performance, it’s essential to have them serviced annually by a qualified local gas-safe engineer.

Regular servicing helps detect any issues early on and keeps your condensing boiler running efficiently, providing you with long-lasting, energy-efficient heating for your home.

Is a Combi Boiler Suitable for My Home?

Whether a combi boiler is suitable for your home hinges on your property’s size and your demands for heating and hot water. Combi boilers are an excellent choice for properties with moderate demand for both central heating and hot water, as they provide both services without the need for a separate tank.

They are also energy-efficient and space-saving, making them a popular choice among homeowners looking to lower their energy bills and reduce their carbon footprint.

Are all new boilers condensing?

Following the introduction of the Boiler Plus legislation on April 1st, 2005, it has been mandatory for all newly installed boilers in the UK to be of the condensing type. This legal mandate was enacted to protect the environment and promote energy efficiency in a home central heating system.

By using condensing boilers, homeowners can significantly reduce their carbon emissions and lower their energy bills.

Do Condensing Boilers Give Off Carbon Monoxide?

Modern condensing boilers, designed to emit fewer harmful gases than their older counterparts, are generally regarded as safe. While they may naturally release small amounts of carbon monoxide, this gas will be safely expelled outside via the flue pipe.

However, if a boiler is deteriorated, it can leak carbon monoxide if it is not burning fuel correctly or the flue pipe is obstructed. To ensure your safety, it’s crucial to install a carbon monoxide alarm in your home and have your boiler regularly serviced.

Does MML Plumbgin Sell Condensing Boilers?

MML Plumbing provides a variety of condensing boilers tailored to your needs and preferences. We are committed to providing high-quality, energy-efficient products that will help you save on your energy bills and reduce your environmental impact.

By choosing a condensing boiler from MML Plumbing, you can trust that you’re investing in a reliable and efficient heating system for your home.

Best large condensing combi boilers

For those seeking a large condensing combi boiler, top options include Worcester Bosch Greenstar 4000, Greenstar 8000 Life 50 kW, and Viessmann Vitodens 100-W. These models are highly efficient and reliable, making them excellent choices for those seeking an effective and cost-effective heating solution.

By choosing one of these top-rated large condensing combi boilers, you’ll enjoy energy-efficient heating and hot water for years to come.

Do I Need a Hot Water Tank with a Condensing Boiler?

hot water tanks with a system boiler

The necessity of a hot water tank with a condensing boiler depends on the type of boiler you decide to install. Combi boilers provide both heating and hot water without the need for a separate tank, making them an ideal choice for smaller homes.

However, system boilers and regular (heat-only) boilers require a hot water cylinder for storage.

Consider your home’s size, heating, and hot water requirements when determining the type of boiler and whether a hot water tank is necessary.

What size condensing boiler do I need?

Establishing the suitable size of a condensing boiler for your home involves considering factors like your property size and heating and hot water demands.

By selecting the right size condensing boiler, you can enjoy efficient heating and hot water while minimizing energy consumption and costs.

How much does a condensing boiler cost?

The cost of a condensing boiler can fluctuate, with prices ranging from £950 to £1,900, contingent on the model and brand. Installation costs are not included in this price estimate.

While the initial cost of a condensing boiler may be higher than a conventional boiler, the long-term energy savings should more than offset this expense. By investing in a condensing boiler, you’ll enjoy reduced energy bills and a more environmentally friendly heating solution for your home.

Best small condensing combi boilers

For those in search of a small condensing combi boiler, top market options include:

  • Vaillant ecoTEC Plus 832
  • Worcester Bosch Greenstar 25i
  • Baxi 600
  • Ideal Logic+ 30

These compact and efficient models are perfect for smaller homes with limited space and provide both heating and hot water on demand.

By choosing one of these top-rated small condensing combi boilers, you’ll enjoy efficient heating and hot water while saving on energy costs and reducing your carbon footprint.

Can you replace a conventional boiler with a condensing boiler?

Indeed, it’s possible to replace a traditional boiler with a more efficient condensing model.

The process involves:

  1. Removing the old boiler
  2. Cleaning and flushing the system
  3. Making any necessary upgrades or changes to the pipework
  4. Installing the new condensing boiler

It’s recommended to have this done by a qualified professional, such as a Gas Safe registered engineer, to ensure a safe and proper installation.

By replacing your conventional boiler with a condensing model, you’ll enjoy increased energy efficiency, lower energy bills, and reduced carbon emissions.


In conclusion, condensing boilers are an energy-efficient and eco-friendly option for home heating.

They offer numerous advantages over traditional non-condensing boilers, such as increased efficiency, cost savings, and reduced carbon emissions.

Whether you’re looking to upgrade your existing heating system or install a new one, condensing boilers are a smart choice that can help you save money and reduce your environmental impact.

With various boiler types and sizes available, you can find the perfect condensing boiler to suit your needs and enjoy comfortable, energy-efficient heating for years to come.

Reliable North London Engineers

Book a gas engineer from MML Plumbing!

MML Plumbing is the go-to choice for professional and reliable combi boiler installation. We are Gas Safe registered engineers and can help you install your new boiler safely and accurately, ensuring optimal central heating performance and peace of mind.

To book an engineer from MML Plumbing, simply contact us at 020 8355 0840 and book an appointment for your combi boiler installation. Experience top-notch service and enjoy the benefits of a new, energy-efficient boiler in your home.

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