A Guide to Combi, Heat Only, and System Boilers.

By Viking Heating

Choosing the right boiler for your home can be a daunting task. With the array of options available, it’s essential to understand the distinct types of boilers and how each one operates to make an informed decision. In this guide, we will explore the differences between Combi, Heat Only, and System boilers, highlighting their Pros and Cons. This will help you determine which boiler best suits your needs.

Combi Boilers

Combi (short for combination) boilers are the most popular type of boiler in the UK, especially in smaller homes and flats. Their appeal lies in their compactness and efficiency. Let’s delve deeper into what makes Combi boilers unique.

1. Space-Saving Design: One of the primary advantages of a Combi boiler is its space-saving design. Unlike other boiler types, a Combi boiler doesn’t require a separate hot water cylinder or cold-water storage tank. This makes it ideal for homes where space is at a premium. The compact unit is usually wall-mounted and can be installed in a kitchen cupboard or a small utility room.
2. On-Demand Hot Water: Combi boilers provide hot water on demand directly from the mains. This means you don’t have to wait for a water tank to heat up, ensuring you have hot water whenever you need it. This is particularly beneficial for busy households where multiple showers or taps might be in use.
3. Energy Efficiency: Since Combi boilers heat water only when it’s needed, they are very energy efficient. There is no energy wasted in keeping a tank of water hot, which can lead to significant savings on your energy bills.
4. Lower Installation Costs: Combi boilers are generally quicker and cheaper to install than other types of boilers because they have fewer components. There’s no need for additional tanks or extensive pipework, which reduces both the cost and complexity of installation.
5. Good Water Pressure: As Combi boilers are fed directly from the mains, they provide good water pressure for showers and taps. This is particularly advantageous in homes where water pressure can be a concern.

Ideal For: Combi boilers are best suited for smaller households or properties with limited space and lower hot water demand. They are particularly advantageous for flats and homes without a loft, as they do not require additional storage tanks.

Heat Only Boilers

Heat Only boilers, also known as regular, conventional, or traditional boilers, are the oldest type of boiler system. They have been a staple in many UK homes for decades, particularly in older properties. Here’s what sets them apart:

System Components: Heat Only boilers require a separate hot water cylinder and two water tanks – a cold-water storage tank and a feed and expansion tank, usually located in the loft. The boiler is connected to these tanks, providing the necessary water for heating and hot water supply.

Hot Water Supply: One significant advantage of Heat Only boilers is their ability to supply hot water to multiple taps simultaneously, making them ideal for larger homes with several bathrooms where demand is high. The hot water cylinder ensures a ready supply of hot water.

Reliability and Simplicity: Known for their reliability and simplicity, Heat Only boilers are less prone to breakdowns compared to more complex systems. Their straightforward design makes them easier to repair and maintain, a preferred choice in older properties where existing pipework can easily accommodate them.

Heat Output: These systems deliver high heat output, suitable for homes with greater heating and hot water demands. They are ideal if your property has larger radiators or needs to heat multiple rooms simultaneously.

Compatibility with Older Systems: Replacing an older boiler in a property with an existing conventional system is straightforward with a Heat Only boiler. It can often be integrated into the existing setup with minimal modifications, making it a cost-effective option.

Ideal For: Heat Only boilers are perfect for larger households with multiple bathrooms and high hot water usage. They are especially well-suited to older properties with existing conventional heating systems. However, they require more space due to the additional tanks, making them less ideal for homes with limited storage space.

System Boilers

System boilers offer a middle ground between Combi and Heat Only boilers. They combine the benefits of both systems, making them a versatile choice for many homes. Here’s how they differ:

System Components: System boilers require a hot water cylinder, but they do not need a cold-water tank, as they draw water directly from the mains. This makes them more space-efficient than Heat Only systems. The cylinder is typically housed in an airing cupboard, providing a neat and tidy installation.

Stored Hot Water: The hot water is stored in a cylinder, ensuring a good supply even if multiple taps or showers are used simultaneously. This makes System boilers suitable for homes with higher hot water demands. Unlike Combi boilers, they can handle the demand for hot water from several outlets at once.

Good Water Pressure: Since System boilers draw water directly from the mains, they provide good water pressure. This ensures a strong and consistent flow of hot water, even when multiple outlets are in use.

Efficiency: They can be a cost-effective solution for homes with moderate to high hot water usage. Their ability to store hot water in a cylinder means that hot water is readily available when needed.

Ease of Installation: Although they require a cylinder, System boilers are generally easier to install than Heat Only systems because they don’t require a cold-water storage tank. This reduces the complexity of the installation process and can lead to lower installation costs.

Ideal For: System boilers are ideal for homes with higher hot water demands but limited space for tanks. They are a good choice for medium to large homes with multiple bathrooms and moderate to high hot water usage. They offer the benefits of stored hot water and good water pressure without the need for a cold-water storage tank.