What is a Combi Boiler?

A combi boiler, sometimes known as a ‘combination boiler’, is the most popular type of boiler in the UK. From small apartments to larger detached homes, you are likely to find a combi boiler somewhere.

But what exactly is a combi boiler – and would this type of boiler be suited to your home? Read on to find out more.

The Combi is a type of boiler that offers both domestic hot water and high-efficiency space heating in one compact unit. They are easy to install and maintain.

A combi boiler provides domestic hot water via hot taps that flow through a heat exchanger, and heated water from the boiler is directed into an external space heating loop through a diverter valve. Not sure what any of that means? Don’t worry! We’re going to cover this in more detail in this article.

But in short, water is heated and distributed through the boiler and pipes. This ensures the optimum temperature and efficiency for your heating.

Why are combi boilers so popular?

Combi boilers use a combination of heat and water to heat up your home. A combi boiler converts 90% of its power into hot water, so it doesn’t need to store water in a cylinder.

This gives you an endless supply of hot water, without the extra cost of hot water storage. That’s why they’re so popular today in the UK.

Plus, they don’t require a water storage tank generally, which is useful for houses with limited space. Another benefit of a combi boiler is that it doesn’t take up as much space as a traditional boiler. This makes it a good choice for apartments and homes that don’t have a loft. Installation also costs less than some other models, as there is less pipework involved.

Combi boilers are very efficient. Because they combine heating and hot water systems, they only need to heat water when necessary. They won’t waste energy while not in use. They are also very convenient and easy to use, thanks to their digital interfaces. They are often easy to install, too.

And if you’re unsure of which model to buy, below are some important things to consider. When choosing between combi boilers, think about your needs and your budget.

What type of boiler do I have now?

When it comes to heating your home, you may be confused about which type of combi boiler is right for your property. This article will help you choose the right boiler type for your property based on your hot water demands, age of your heating system, and the pressure of your mains water supply. If you’re not sure what type of boiler you have, take a look at these pictures to get an idea of what your options are.

There are several different types of boiler, but they all have their advantages. First of all, a combi boiler is easy to replace – you won’t need to replace your hot water cylinder or loft tank.

In addition, you can install this type of boiler with a reduced water pressure. In addition to its many advantages, a combi boiler can also save you money on energy bills because you don’t need to heat water from different sources.


So, what exactly is a Combi Boiler?

A combi boiler is a popular heating device, and is now used by over 70% of UK homes. This type of boiler combines a water heater and central heating unit into one compact unit. Instead of having separate water tanks, a combi boiler uses a coil to heat water that runs to a tap. Unlike a conventional boiler, combi boilers can provide both hot water and central heating instantly, which is a great benefit for people with small homes.

A combi boiler is simple to use, and can either be wall-mounted or stored in a cupboard. It produces heat when it is ignited and sends the water through heat exchangers.

The water passes through the pipes and rises in temperature as it travels through them. The unit is usually equipped with a room thermostat to ensure that it runs correctly. It is also energy-efficient, so you can save money on your energy bill while heating your home.

For information on costs and how much a combi boiler costs, read this.

How does a combi boiler work?

A combi boiler includes all of the elements necessary to provide hot water to your home. It heats water from the mains, and the hot water is then transferred to your taps. Because it uses a stainless steel direct heat exchanger, the boiler transfers heat from the water inside it to clean, cold water outside. Combi boilers have a heat store, or water reservoir, that never drops below fifteen litres.

Combi boilers are efficient because they can heat water on demand. They do not store hot water in a tank, so they are perfect for small homes. Combi boilers are also popular because they do not require a hot water storage tank or cold water feed tank.

You only need hot water when you need it, rather than constantly heating the water inside. A combi boiler is the most energy-efficient choice for a small house.

A combi boiler works by detecting the demand for hot water in a house. When you turn on the hot water tap, the unit heats the water in the mains and delivers it to the taps or shower. Because it only heats water when you need it, you can avoid the need for an extra pump. The water is delivered directly to the taps and is ideal for homes where hot water is not a luxury.

Is a Combi Boiler suitable for my home?

If you’re unsure about which type of boiler is right for your home, you’re not alone. Several factors will affect the size of your boiler, including how many radiators you need to heat, the number of bedrooms, and how many bathrooms your home has. The right size boiler depends on the size of your house, as a smaller boiler will be inadequate for a smaller home. If you’re unsure, you can always contact a boiler installer for a free no-obligation quote or use our 100% free comparison tool.

In short: a combi boiler is suitable for most types of homes.

There are three main size ranges – 24 to 27 kW, 28 to 34 kW, and 35 to 42 kW. Each size range has their own advantages and disadvantages. You should also consider the size of your property to make sure a combi boiler will fit the space in your home. For example, if your home has three bedrooms, you need a combi boiler with a power output of between 29 and 35 kW. Confused? Let us do all the legwork for you.

Can I get a free combi boiler?

It’s possible that, under various government schemes, you can get a free boiler (commonly called a boiler grant). For more information on UK boiler grants, read this first.

What size Combi Boiler do I need?

You’ll need a suitable boiler size suited for your home, obviosuly.

A small boiler may not provide enough hot water to take a bath, and an over-sized boiler will be unsuitable for your home.

A medium-sized home requires a boiler of a size that will provide ample hot water and heat your home without overheating the house. An oversized boiler will waste gas and increase your heating bills. Plus there is talk of banning gas boilers. When choosing a boiler, make sure to look for energy efficiency and a high-quality hot water tank.

Your home’s size and number of radiators will help determine the kW required for a combi boiler. A medium boiler should provide sufficient hot water for a three-bedroom flat. A four-bedroom house, on the other hand, will require a larger boiler that can provide hot water for more bathrooms and more radiators. A large boiler with twenty radiators will need a 35-42kW output, while a smaller one will need a smaller 24-29kW unit.

Pros (positives) of Combi Boilers:

The Pros of Combi Boilers include space saving, higher efficiency, and energy savings. Combi boilers are a smart choice for those who want to save on energy bills and the environment. They use a small amount of energy to produce hot water that is only needed on demand. Combi boilers are also less expensive to install than separate water heaters and furnaces because they require less materials and labor to install.

However, there are some cons to using a combi boiler. First of all, you must be sure that the mains pressure in your area is high enough to supply the boiler with adequate water. Secondly, it’s important to make sure that you have enough water pressure in your home, as a low pressure will lead to significant expenditures and long-term damage. Lastly, you need to have a professional engineer to install one. While a combi boiler is easy to install, it’s recommended that an expert engineer installs it.

A combi boiler’s main drawback is that it can limit the amount of hot water you can use – see the below section for more. It can limit the amount of water you can use until the heating element reaches the right temperature, which may take a few minutes. If you have multiple bathrooms or multiple occupants, it may be best to avoid combi boilers.

So to summarise the positives of a combi boiler:

  • Small, so saves space
  • Easy to install, doesn’t require significant changes to existing pipework
  • Highly efficient and cheap to run
  • No water storage tank needed

Cons (negatives) of Combi Boilers:

While the benefits of a combi boiler far outweigh the disadvantages, there are certain cons to consider before you purchase one. Combi boilers are dependent on mains water pressure to operate and a lack of it can lead to long-term damage and expensive repairs. Therefore, they are not suitable for rural households where the water source is limited. Although there may be abundant streams in such areas, you should still take this disadvantage into consideration before you buy a combi boiler.

The most common type of combi boiler is electric. While it can sometimes be expensive to buy, it’s 99% efficient and does not require a flue. An electric combi boiler doesn’t need to break the bank, you can buy them yourself from Screwfix or other merchants. has the added advantage of being safer, as it has no carbon monoxide risk. However, if you are concerned about running out of hot water in the middle of the night, you should consider buying a gas combi boiler instead. The cons of electric combi boilers are that they are not as versatile as gas boilers and can only heat water on demand.

With the help of articles like this one (hopefully!) you’ll now have a better idea of he pros and cons of a combi boiler before purchasing one. We compare boiler prices including combi boilers, and these prices include installation.

And to summarise the negatives of a combi boiler:

  • Not ideal for larger houses or those with high usage
  • If existing system is not using a combi boiler, replacement costs can be high
  • Can generally only heat on demand
  • Will not function during a power-cut (electric)

If you’re looking for a new combi boiler and want to know how much they cost, then compare prices with us. We compare companies like Heatable, Housewarm, BoilerCentral and many more!

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