How Does a Combi Boiler Work?

how does a combi boiler work

Combination boilers are among the most popular heating systems on the market, designed to provide an efficient means with heating water while simultaneously heating your home. But how does a combi boiler work? This helpful guide will give you all the information you need.

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What is a Combi boiler?

A combi boiler is one of the most modern and used boilers, having earned its own distinctive place in the UK’s boiler market.

Combi boilers need to be wall hung or placed in a kitchen cupboard and have no cylinder or tank unlike system boilers or regular boilers.

Combi boilers have two tasks to do as below:

  1. Power central heating (radiators etc.)
  2. Heat water for taps, showers and baths.

When you add both of these together the term is described as ‘combi’. The function of a combi boiler is really as simple as that.

Even though they’re efficient and save money, when researching for the best combi boiler, you also want to check how long the parts and labour warranty period is for.

At Boiler CentralViessmann offers a massive 15-year warranty. We are the only company in the UK to offer this tremendous warranty.

How Does a Combination Boiler Work?

A combination boiler works by controlling the entire central heating system in a single system, providing superb space-saving, and cost-reducing, features.

As mentioned, the combi boiler takes the water from the mains. When the hot water tap is switched on, the gas burner is also alerted, and then the heat exchanger transfers the energy to water.

Combi boiler sounds complicated, but the process of how they operate is quite simple.

Below are some bullet points to review how a combi boilers work:

  • Combi boilers do not need a cold-water storage tank and a hot water tank.
  • They use radiators to supply heating around the home.
  • When the hot tap is turned on, the boiler starts to work.
  • They take water from the mains, the gas pipes up, produces heat, makes the water hot and then kicks the water to the source.
  • There are valves to direct water flow to the central heating system and to the water output way.

Remember combi boilers do not come with hot water storage tanks. This is brilliant if you are short of storage space.

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Who are combi boilers suitable for?

More and more people are changing their old and inefficient boilers to combi boilers.

Combi boilers are suitable for anyone who has a home that is requiring hot water on demand.

They usually are best for homes that have less than 4 bathrooms or do not have a huge amount of hot water requirement on demand.

Combi Boiler Home

If the home has a high demand for hot water, such as a home with 4 family members getting a shower in the morning, then a system boiler is the best option.


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Types of combi boilers 

There is a range of different types of combi boilers available on the market depended on the energy source of the property. House

On the basis of the energy source, you can choose one from a wide range of fuel sources.

Four types of combi boilers are available depending on fuel type:

  1. Gas combi boilers: These are the most used combi boilers and use natural gas as a fuel source. Considering cost minimisation and natural gas burning this can be the best option and most cost-effective.
  2.  Oil combi boilers: Oil is used here as the energy source. People who have a scarcity of gas are best to choose this type. They need a tank to store oil and a connection to it, but most customers who ask for oil currently have the provisions set up already.
  3. LPG combi boilers: LPG or Liquified Petroleum Gas, is also used by some combi boilers as a fuel source. LPG combi, demand for storage tanks to store LPG and connection from the tank.
  4. Electric combi boilers: Electric Combi boilers are slightly different from others, and can increase your monthly electricity bills quite significantly. Not a good choice for large households and very uncommon to be found in large homes.

Cost of the best Combi boilers 

Here are some best Combi boilers on the market along with descriptions according to cost (without installation), brand, and efficiency.

Company Name





Ecotec Plus

£1000 – £1400

Up to 10 years

Worcester Bosch

Greenstar i

£800 – £950

Up to 7 years


EcoBlue Advance

£1000 – £1300

Up to 10 years



£700 – £900

7- 10 years


Vitodens 100-W

£900 – £1000

Up to 15 years

Advantages of a Combi boiler 

Some lucrative advantages have made combi boilers very common in the households of the UK. These are:

  •  Hot water on demand: Day by day, people are getting busier. They have not a single moment to waste. So, getting hot water just on demand is very attractive to homeowners.
  • Less energy needed: Combi boilers consume lower energy.
  • Less space occupation: Requirement of no water tank (for both hot and cold water), made combi boilers suitable to have a place in almost all types of properties.
  •  Higher water pressure: Although combi boilers don’t need an extra water tank, they are surprisingly capable of supplying water with great demand.

Now you know how a combi boiler works

If you still need some information on what a combi boiler is, how they work or have any specific questions, then we are on hand to help.

If you want to get a new boiler, then you can get a fixed price online and buy your new boiler online from as little as £17 per month.

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