Combi Boiler vs Regular Boiler vs System Boiler, What's the difference?

With so many different types of boilers on the market, it can be a challenge to understand what the difference is between them all. So we've put together a comprehensive guide to help you understand the difference between a Combination boiler, Regular boiler, and System Boiler, three of the most common boilers you will find in domestic households.

Combi boiler lifestyle

What is a combi boiler?

A combination boiler, or combi boiler as it is most commonly known, provides both heating and hot water for your home directly from the mains. It is the most common type of boiler for domestic heating in the UK as it combines both a water heating system and a central heating boiler system all in one box.

Our in-depth guide on 'what is a combi boiler' fully outlines how they work in more detail, the different types and suggestions for the best type of combi boiler.

How does a combi boiler work?

A combi boiler works by taking water from the mains water supply and heating it with a heat exchanger to the required temperature instantly, meaning there's no need for a separate water tank. When it comes to central heating, the water is heated based on the instructions given to the boiler, via custom settings or a heating system that uses a room thermostat to activate.

What is a regular boiler?

The most traditional type of boiler on the market, the regular boiler (also known as a conventional boiler, will only provide heating for your home, no hot water. It is often found in older homes that are yet to move to more modern boilers. These systems require a large amount of space for installation due to the need for a cold water cylinder and cold water cisterns.

How does a regular boiler work?

A regular boiler works by heating cold water from the water tank using a hot water storage cylinder. The hot water is pumped around your home through the pipes in the radiators, providing heat to each room of your home.

What is a system boiler?

A system boiler is a type of boiler that is often found in larger properties as it can meet the increased demands of a bigger household. System boilers can use 3 different types of fuel: Gas system boilers, Oil system boilers, and LPG system boilers making them very versatile boilers to have in the home.

How does a system boiler work?

A system boiler functions in a similar way to a regular boiler system, but not a combination boiler as it is not connected to the mains. System boilers can provide the heat for your central heating system and, using a separate cylinder or water tank, provide a constant supply of hot water throughout the home.

If you're looking for further comparisons of the advantages and disadvantages of different types of boilers you can get to know the different types of boilers on our blog

Is a combi boiler a condensing boiler?

A condensing boiler works by recycling the wasted exhaust gas that is created during a boiler's normal operation. By re-using the exhausted gas, water vapour and steam back through the system, some of the heat and water is retained making the boiler's operation more efficient.

However, it is now a legal requirement that all newly installed combi boilers are condensing boilers, to help improve efficiency. This is also the same if you are upgrading your regular boiler or system boiler, they too have to be upgraded to condensing boilers. Therefore, all new combi boilers are condensing boilers.

Condensing boiler regulations

In 2018, the Department for Business, Energy and Industrial Strategy implemented Boiler Plus Legislation. This legislation was introduced to help reduce CO2 emissions produced by non-condensing units and to drastically increase the energy efficiency of residential boilers. All new boilers installed in the UK must meet these new standards. A summary of the most important legislation can be found below:

  • Gas-fired boilers, both new installations and replacement, must be condensing
  • Oil-fired boilers, both new installations and replacements, must be condensing
  • All installed condensing boilers must have an efficiency rating no lower than B.

Further advice

If you need further help or advice for choosing the right boiler for your home, contact our experts at PlumbNation so we can help you make the right decision today or check out our collection of guides on all things boilers.