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Types of boilers


When it comes to choosing the best type of boiler for your home, there are plenty of different factors to consider. The size of the property, the number of bathrooms, the number of showers, the area’s water pressure, and the type of property should all be significant considerations when it comes to choosing your domestic boiler system. We’ll take you through the three most common types of boiler for UK properties, explaining the unique properties, advantages, and disadvantages, and ecological impact of each one, giving you some insight into which boiler replacement is the most practical choice for your home.

Condensing Boilers

By law, every new combi boiler, system boiler, or conventional boiler that’s installed in the UK has to be a condensing one. It’s not a type of system so much as a property that all units must now possess. Condensing boilers have a larger heat exchanger and use the latent heat as fuel, which would usually escape into the atmosphere, helping to increase energy efficiency and lower your utility bills and your carbon footprint. When it comes to energy efficient boilers, there’s no better alternative – condensing boilers are actually more than 90% energy efficient and a very green home heating solution.

There are three main types of condensing gas boilers: combi boilers, system boilers and conventional (also called traditional, regular boilers, open vent or heat only boilers) boilers.

Combi Boilers

Combi boilers are probably the most cost-effective residential boiler for most homes. They control both hot water and central heating, and their energy efficiency makes them the unit of choice for environmentally-conscious homeowners. Heating water directly from the mains and whenever a tap is turned on, you can get unlimited hot water whenever you need it. There’s no need for a cylinder or water tank, saving you space in your home and cutting down the installation time.

In addition, boiler efficiency ratings generally rank them as one of the highest types of A-rated boilers on the market. Helping to substantially reduce heating bills and save space – there’s a reason why they’re one of the UK’s most popular choices when it comes to home heating.

Combi boilers have plenty of advantages for homeowners:

  • Responsive to tap usage and temperature
  • No waiting time for hot water and central heating
  • Compact choice for homes with less space
  • Water delivered directly from the mains
  • Provide powerful showers without the need for a pump
  • Easier to maintain since there’s generally less pipework to be installed
  • Much lower risk of pipework freezing
  • No need for loft space

However, a combi boiler may not be the best choice for all homes and there are some drawbacks:

  • May not be the best choice for homes with low water pressure
  • Not possible to run two baths or showers at the same time
  • Leaks can cause loss of water pressure
  • Not ideal for larger homes
  • May not be compatible with your shower
  • Require a good level of mains pressure

System Boilers

If your home has more than one bathroom, a system boiler could be the perfect option. They require a hot water storage cylinder, but not a water tank, and because many of the main components are actually built into the system, your boiler installation will be relatively quick and painless. Both the pump and the expansion vessel are inbuilt, eliminating the need for header tanks. As there’s no need for a tank, a system boiler frees homeowners from worrying about frost damage or leaks, while it also makes them much easier to maintain. For larger homes with multiple bathrooms, particularly if there’s no space for a tank, system boilers are a great choice.

Their benefits include:

  • Economical running costs
  • Compact and space-saving design
  • Constant supply of hot water
  • No need for an expansion cistern
  • Compatible with solar thermal systems, making them a very energy-efficient option

Unfortunately, they do have some disadvantages:

  • May have to wait for hot water to reheat if it runs out
  • Need to find space for the cylinder
  • Size of your tank dictates how much water you can use
  • Requires insulation in order to stop heat loss

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Conventional Boilers

Conventional boilers, also known as traditional, regular, open vent or heat only boilers, are comprised of both a cylinder and a water storage tank. Although they’re not the best option if space is at a premium, a conventional boiler is able to supply large volumes of hot water to multiple bathrooms, making them a great choice for larger households. It’s probably best to remember that this sort of unit is best suited to homes which already have traditional heating systems in place. Your pipework may not need changing at all, but if it does, any changes are likely to be minimal. Like system boilers, they can be used in conjunction with solar heating systems, helping you to reduce your energy bills and ecological footprint.

Advantages include:

  • Can supply water to multiple bathrooms and taps at the same time
  • Ideal for homes in areas with low water pressure
  • Compatible with solar thermal systems, making them a very energy-efficient option

While some of the downsides are as follows:

  • Not a compact option
  • Hot water isn’t available on demand and may need time to warm up
  • Installation can be more expensive and complicated due to the need to install both a cylinder and a tank

What Type of Boiler Do I Need?

When you look for a replacement boiler, it’s best to keep in mind that every home has different heating requirements, and that every different boiler system has a range of unique properties. In general, tank-based home boilers (system and conventional) are best for properties with multiple bathrooms, while combi boilers are the most appropriate choice for smaller homes with just one bathroom.

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Video transcript

Welcome to Hometree, home of the stress-free boiler installation.

What is a condensing boiler?
If you purchased a boiler after 2005, chances are that it is a condensing boiler, a high-efficiency boiler. Rather than being a ‘type’ of boiler - such as combi boiler, system boiler or conventional boiler - the term ‘condensing’ refers to the way it functions.

There are three main types of the gas boiler - Combination (or combi), System and Regular.
If you are unsure about the type of boiler you currently have, these two simple questions will help

  1. Do you have a hot water cylinder? (this is usually in a cupboard or airing cupboard)
    No - You have a Combi Boiler
    Yes - You have a Regular or System Boiler

  2. On the Boiler, Is there a Pressure Gauge?
    No - You have a Regular Boiler
    Yes - You have a System Boiler

Boilers can be confusing, especially when you are looking for a new boiler. When you know a little about the boiler types - discovering the right replacement gas boiler for your home can be easy.

A Combination boiler is a simple unit that delivers both hot water and heating, which makes them great for small to medium-sized homes. Combi boilers heat water directly from the mains, whenever you turn on your hot tap.

If you are buying a new combi boiler, you don't need a hot water storage cylinder or a cold water storage tank in the loft, so they save space too.

Unlike gas combi boilers, a system boiler need a cylinder for storing hot water, but they don't take up space in your loft. With a system boiler, some of the main heating and hot water system components such as the pump are built into the boiler itself, so it's quick and easy to install.

A System boiler is ideal for homes with two or more bathrooms as it can allow you to have multiple showers running at the same time.

A Conventional boiler, also called regular, open vent or traditional boilers, need both a hot water cylinder and a tank in the loft to store cold water. This type of boiler is perfect for homes where a lot of hot water is used at the same time and are particularly well suited to low water pressure areas and installing into systems which have lots of old radiators.

Hometree can discover which type of boiler, boiler model, make and size is suitable for you in 90 seconds just by asking some simple questions on our website or over the phone. We will provide you with an A-rated boiler and full installation, at a great price and at a time that suits you. We give you a free smart thermostat and a 10-year warranty.

Unlike some traditional boiler installers, we won't send pushy salespeople to your home; instead, when the time comes to complete a survey of your current boiler we will do a video survey using your smartphone.