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Pros And Cons Of A Combi Boiler

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  • Combi Boiler, Combination Boiler, Features of Combi Boilers
  • Posted date:
  • 09-11-2022
Pros And Cons Of A Combi Boiler

What is a combi boiler?

A combi boiler is a fantastic boiler type that delivers instant hot water and heating. One of the most significant benefits of a combi boiler is that they don't require the extensive storage that comes with cylinders or storage tanks, so they take up less space. Everything your household requires to generate heat and hot water on demand is stored within the boiler.

However, we mustn't forget their limitations, such as the fact they sometimes struggle to meet high demands for domestic heating and hot water in much larger households and properties. Many more significant properties require extra help from a hot water cylinder and cold water tank.

Yet, modern combi boilers do not include these, which makes them more compact yet unsuitable for smaller homes. If you're struggling to decide which boiler type would be best suited to your household, contact us today Hampshire Emergency Plumbing and Heating, and our professional, qualified boiler engineers will be on the line to provide a free site survey and any advice. 

What is a conventional boiler?

The conventional boiler is recognised by various names, such as open-vent, regular and heat-only boilers, as they are one of the oldest boiler types available in the UK. The conventional heating system includes tanks and heated water cylinders installed into the household loft or airing cupboards.

The cylinder is where your domestic hot water is generated and stored until you switch a hot tap on, and often, the tank in your loft is where cold water is kept. The tank delivers water down to your cylinder and boiler.  Such means that conventional boilers and their external parts require plenty of storage space, so you must ensure that you have the available space within your home or property.

All parts are also connected by various complex and individual pipelines, which is why a conventional boiler is best suited to those who already have conventional boilers in their homes, as the installation process isn't as much of a hassle. 

What is a System boiler?

System boilers offer homeowners the best of both worlds as they are piped directly to your mains water supply, and yet they also utilise cylinder tanks in which you can store water. In providing both options, system boilers can better meet high heating and hot water demands throughout the home without needing to store your tank in the loft space and have extensive installation. 

Combi vs conventional boiler costs

A combi system can be a fantastic option for those with single bathrooms or potentially two based on the output rating of the existing boiler in your area. These are the reasons why:

 It can help you save space in your home as it does not require a hot water cylinder or tank from an immersion heater.

 When you need it, It will send the hot water immediately to your taps or electric showers.

 Its installation is quick and straightforward, taking at most two day

 The cheapest form of boiler replacement is a combi-for-combi

However, combi boilers are fantastic, yet they are most suitable for small or medium-sized households. If you live in a much larger property with numerous bathrooms, we recommend you opt for a system or convention boiler because:

 Combi boilers aren't suitable for homes that have weak mains pressure

 Combi boilers struggle to meet the high demands for water in homes with more than one or two bathrooms. 

Best combi boilers


Baxi has provided the country with highly efficient manufacturing products since 1866 and has been a frontrunner with an impressive 200 manufacturers across the UK.

They provide regular/conventional systems and combi boilers with a broad range of heat outputs that are straightforward to maintain and easy to install, and these are how best they are recognised. Baxi boilers are lightweight models that make for easier installation. They offer the UK's most affordable, cost-effective prices compared to a whole host of other reputable brands throughout the country. 


Ideal heating has been manufacturing boilers in Hull since 1906 and works daily to meet the demands and ever-changing needs for heating homes across the UK. They provide an extensive collection of boiler types, for example, system, regular and combi boilers.

Whilst they only produce gas-fuelled boilers, they can also convert their models to sufficiently run using LPG (Liquefied Petroleum Gas). The conversion of fuel makes these boiler types highly accessible for homeowners that aren't national gas grid connected. 


The Vitodens have a gas boiler range of some of the best-selling Viessmann products, including heat-only (regular/conventional), system, combi and storage combi boilers. The range includes the following:

  • Vitodens 111-W Storage Combi
  • Vitodens 222-F Storage Combi
  • Vitodens 050-W (Combi & System)
  • Vitodens 100-W (System, Combi & Heat-Only)
  • Vitodens 200-W (Combi & System)

Vitodens gas boilers are known for being compatible with various types of gas alongside natural gas.

In doing so, your brand-new gas boiler can combine with various sustainable biofuels and fuel alternatives, making them a highly environmentally friendly option for households across the UK.

The newest boiler models are ready for the switch to hydrogen usage as they are designed to run on 20% hydrogen. 


Vaillant provides homeowners with two main boiler models, the Vaillant ecoFIT and the Vaillant ecoTEC, which are accessible in regular, system and combi boiler types. You can also purchase ecoTEC boilers in the form of storage combi boilers that include their own integrated hot water storage tank, meaning you don't require extra space to store it as the tanks are built-in. 

Worcester Bosch

The Worcester Bosch consists of a wide range of boilers with various types of fuel options. Their models provide numerous natural gas boilers alongside oil boilers for homeowners that aren't directly connected to the national gas grid. Within their gas boiler range, each available model is approximately 20% hydrogen, meaning that if hydrogen blend gas enters mainstream availability, the Bosch boilers will benefit massively from the change.

Its units are incredibly future-proof in the most environmentally friendly way that will also assist you in saving money, as you won't have to go through the upgrades. Worcester Bosch offers regular (conventional) systems and combi boilers with plenty of different fuel options and power outputs to accommodate various types of homes throughout the UK.

Advantages and Disadvantages Of A Combi Boiler

Combi boilers, also known as combination boilers, have seen their popularity increasing rapidly in the United Kingdom over the last few years. More than 70% of households prefer to install combi boilers in kitchen cupboards over the tank system or hot water boilers that need to be stored away in other areas of the home because of their efficiency rating and compactness.

Significant features have enhanced the popularity of combination boilers across the UK, making them the most popular boiler. Combi boilers offer various benefits, which is why they are preferred and recommended by most boiler engineers.

Benefits Of Combi Boilers

When compared to standard boiler models, they tend to be more productive. Combi boilers are relatively affordable as they can save you more than £300 annually if you decide to replace your standard model with a combi boiler.

More energy-efficient boiler models will allow you to be more eco-friendly, as it will ensure you don't lose heat in large percentages and help save money on heating bills. 

Compared to traditional boilers, combi boilers are easier to install, meaning installations are affordable. Finding the replacement parts of combi boilers is more accessible than traditional ones in case of a problem.

Since there are no water tanks for heating up, combination boilers can offer a sufficient unlimited supply of hot water within a reasonable amount of time.

Combi boilers assume little space compared to standard heating systems because a separate water tank is unnecessary. It makes them perfect for households with space limitations.

The cold water stored in a combination boiler system is safer for drinking since it comes from the source. Older systems keep the cold water in tanks even before it's piped around the household.

A combination boiler system is not prone to low pressure, and there are fewer chances of suffering from airlocks since the warm water is pulled from the primary source.

A combination boiler is not susceptible to the build-up of sludge leading to airlocks. The water is drained from the primary source and not stored in a cylinder or tank where it can attract dust and debris, meaning it will require a power shower from a qualified engineer.

The rise in popularity of combination boilers indicates that most boiler experts are well trained in matters concerning repair and servicing them. Combi boilers, like any other old or new heating system, have their drawbacks. Irrespective of their popularity, there are numerous concerns you must consider when thinking of replacing your boiler and ensuring it functions correctly.

The Disadvantages Of A Combi Boiler

Combi boilers function correctly in the presence of the appropriate pressure levels from the mains supply. When having a brand new boiler, you need to consider the pressure being generated by the mains in your area before installing your combi boiler.

Combi boilers cannot run multiple flows of water simultaneously. It's also not possible to open the hot water tap while taking a shower. Such can become an issue if you reside in a household with multiple bathrooms or many people.

Since there are no water tanks, if your combi boiler breaks, it will leave you with no warm water or central heating.

If you require combi boiler installation in Southampton and the surrounding areas, contact our specialist heating engineer today. Follow the link to find  boiler installation near you.