Advantages and Disadvantages of a Combi-Boiler

A combi boiler owes its name to the fact this variety of boiler functions as a dual hot water and central heating boiler. Below, you can find a concise overview of the advantages and disadvantages of this boiler type.

What is a Combi Boiler?

A combi boiler, which is short for combination boiler, is a compact boiler type that has become a popular heating solution in many UK homes. It’s called a combination boiler because it integrates central heating and hot water production into one single appliance.

Combi boilers are highly efficient and space-saving, making them ideal for smaller homes or flats where space is at a premium. They don’t require bulky water tanks or cylinders as they heat water directly from the mains. This feature also means you get unlimited hot water on demand – so no more waiting for a water tank to refill or a cold water unit to heat up.

How Does a Combi Boiler Work?

A combi boiler works by drawing gas from the mains and burning it to heat water. This heated water is then used directly for central heating and providing hot water on demand.

  • Water supply – as soon as you demand hot water, the boiler draws cold water directly from the mains supply. This means you’re always using fresh water.
  • Heating up the water – inside the combi boiler is a heat exchanger. When water passes through this component, it’s heated up quickly. This process is typically powered by gas or oil, which burns to generate the heat.
  • Instant heating – Once heated to the right temperature, the water is then sent directly to your taps or radiators. Unlike traditional systems, there’s no need for the water to be stored in a tank as it’s delivered instantly.
  • Safety features – safety is paramount in combi boilers. They come with various safety mechanisms like pressure relief valves and automatic shutdown to prevent overheating or pressure build-up.

The Benefits of Choosing a Combi Boiler

There are many advantages of a combi boiler. See below for the main reasons why people choose to go for this type.


It’s an Environmentally Friendly Boiler Choice

Combination boilers tend to stand out for their eco-conscious design.

Modern models are often built with a focus on minimising environmental impact, incorporating features that work to reduce greenhouse gas emissions. This is particularly relevant today as there is a growing emphasis on making eco-friendly choices in our everyday lives.

A Combi Boiler Offers a Space-Saving Design

When compared to conventional boilers, a combi boiler offers a much more compact design. This is because they don’t require a hot or cold water storage unit or tank, which is typically found in airing cupboards with conventional systems. This means they can fit easily in smaller spaces, making them ideal for those living in both small homes or who would prefer the boiler to be placed in a more discreet place.

Opting for a combi boiler can free up a lot of additional storage space in your home, such as in the attic or roof area – since there’s no need for a cold water storage tank. The direct mains water supply to these boilers not only saves space but also simplifies installation.

Plus, without a cold water tank, there’s a reduced risk of pipes freezing in colder seasons, which is a common problem here in the UK.

They’re Energy Efficient

A combi boiler is known for its energy efficiency, mainly because they are able to provide hot water on demand without the need for a separate hot water tank – reducing heat loss and saving energy. Their compact size and the fact that they only heat water as needed make them a much more efficient option when compared to traditional boilers.

Quick Heating and Hot Water Supply

As we’ve touched on throughout this article, a combi boiler provides instant access to hot water and central heating.

They heat water exactly when you need it, making them highly convenient for homes with high demand for hot water. For example, a family home where multiple people need instant hot water to use a bathroom consecutively.

Unlike traditional boilers, there’s no risk of running out of hot water as it’s not stored but heated instantly.

Combi Boilers Are Cost Effective

Combination boilers are also cost-effective in the long run. They heat water in smaller quantities as and when you need it, unlike traditional boilers that heat large volumes of water regardless of the actual usage. This not only reduces energy consumption but also lessens the environmental impact.

combi boiler

The Disadvantages of a Combi Boiler

Although a combi boiler is a great choice for many, there are a few disadvantages to these types of boilers that are worth being aware of.


A Combi Boiler May Struggle to Meet High Demand for Water

In larger households or where multiple hot water outlets are used simultaneously (e.g. showers and kitchen taps), there can be an issue with hot water demand.

Some combi boiler models struggle to supply multiple outlets simultaneously, and it’s known as one of the biggest disadvantages of combi boilers. This is especially true in homes with more than one bathroom.

So, although they are efficient for the majority of households, their performance may drop in larger settings where the demand for hot water is higher and more frequent.

Water Pressure Issues

Following from the above, combi boilers depend heavily on the main water pressure to function effectively.

So, if multiple taps or showers are used at the same time, the water pressure can drop, leading to a weak flow. This can be particularly problematic in homes with higher water usage or where the mains water pressure is already low.

No Immersion Heater for Backup

Conventional hot water systems often include immersion heaters that store hot and cold water supply tanks as a backup. This allows for hot water availability even if the boiler fails. Combi boilers lack this feature.

In the event of a combi boiler breakdown, there is no reserve of hot water, leaving the household without any hot water supply until the boiler is repaired. This can be a significant inconvenience, especially in colder months or for large families.

There Can Be a Longer Wait for Hot Water

With modern combination boilers, when a hot water tap is turned on, the water must travel through the boiler to be heated before reaching the tap. This can cause a slight delay if you were to compare this process to a traditional boiler type that has access to a hot water tank, where the water is pre-heated and readily available.

So, the fact that combi boilers heat water with a slight delay is, of course, only a minor inconvenience, but it’s more noticeable in larger homes where the distance from the boiler to the tap is greater. The wait time for hot water can be a particular issue in busy households where the demand for immediate hot water is higher.

The Costs Associated with Combi Boiler Installation

The initial installation cost of a combi boiler can be higher than that of conventional boilers, especially if you are transitioning from a full system boiler with a separate hot water tank. This cost includes not just the price of the boiler itself but also the installation and any necessary alterations to your home’s existing heating infrastructure.

Although the initial installation cost of a combi boiler can be higher, this shouldn’t be seen purely as a disadvantage.

This cost is a reflection of the combi boiler’s modern and efficient technology, and it includes not just the boiler itself, but also installation and necessary modifications to your home’s heating infrastructure.

For example, if you’re moving away from a more conventional boiler system with a hot water tank, the process involves removing the tank and upgrading your plumbing to suit the new, more efficient system. So, although there is an upfront investment – it’s important to remember that combi boilers are generally more energy-efficient, leading to long-term savings on energy bills.

Is It Worth Investing in a Combi Boiler?

Generally speaking, a combi boiler system tends to be a smart choice for many homeowners, mostly due to the integration of heating and hot water in one efficient system.
The design of modern combi boilers also caters to modern living, where maximising space and reducing energy consumption are usually key considerations.

As we’ve highlighted in this article, they are particularly well-suited to small or medium-sized homes, as well as apartments where space is a key consideration. The on-demand nature of combi boilers aligns well with energy efficiency, contributing to a more sustainable lifestyle whilst also potentially reducing energy bills.

Additionally, the ease that comes with having only a single appliance handling both heating and hot water offers a simplicity that appeals to many who are seeking a more practical and effective solution for their home comfort needs.

Call for a Quote on 0151 203 3771

An engineer is available to survey your home for free before boiler installation takes place. We provide boiler installation services in the Liverpool, Wirral, Cheshire, Manchester and North Wales area. Call 0151 203 3771 or contact our office for more information.

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