Types of Boilers Explained: Combi, Conventional & System (Which Is Right for You?)

Gas boilers began appearing in UK homes in the 1920s.

But it wasn't until the discovery of North Sea gas in the 1960s that they became widespread.

And since then, their technology has advanced and branched off into several directions. 

Read on to learn how different boilers work and how to choose the right one for your home.

What type of boiler do you actually need?

Different types of boilers suit different households' heating and hot water demands.

So, before you choose a new boiler, ask yourself these four questions:

• How many people live in your house?
• How many bathrooms do you have?
• How much free space do you have?
• How much hot water do you need?

Replace or repair?

Sometimes it's worth upgrading to a whole new type of boiler. 

Other times, you may simply need to repair what you have.

It all depends on your budget, plans and current boilers' condition.

For example. Will you be selling your home soon? 

New boilers can add value to homes, but it depends on the type, age, and energy efficiency rating of the model you choose.

There are other considerations to make, too. 

E.g., If you're replacing an older system, it's also worth considering a power flush before connecting a new boiler.

Types of boiler in the UK (in order of most to least common)

1. Combination (Combi) Boilers

Combi boilers first came to the UK (from Germany) in the 1960s.

They became widespread here in the 1980s and today they are the most popular type of UK boiler.

Combis are designed to provide heat and hot water without the need for bulky water tanks and cylinders.

To achieve this, they are made up of single, compact unit. 

It heats water directly from the mains when you turn on a tap.

They’re ideal for people who have limited space or who simply want to limit the space a boiler takes up. They can also heat water on demand.

However, this type of boiler needs to be re-pressurised more often than regular boilers.

Pros:

• Instant hot water: It heats water on demand, so it never runs out.
• Space-saving: There is no need for bulky water tanks or a hot water cylinder.
• Highly efficient: It only heats the exact amount of water you need.

Cons:

• Lower pressure: Flow reduces if multiple taps are used at once.
• Total system failure: If the unit breaks, you lose both heating and hot water.
• Mains dependent: They do not work well in areas with low mains water pressure.

2. Conventional Boilers

Conventional boilers (also known as regular, heat-only, or open-vent boilers) were the original gas boilers in the UK (before Combi boilers overtook them in popularity). They use:

• A boiler unit
• A hot water cylinder
• Two water tanks (usually stored in the loft).

Their water cylinder's storage means provides hot water from multiple taps at the same time. 

But they can only provide the amount of hot water that’s been stored in the cylinder. 

They suit older homes in low-pressure areas, too. This is because they use gravity rather than the cold water mains water supply.

If you need a new boiler and already have an older system, they are often more cost-effective and less disruptive to replace. 

You wouldn’t need to lay down more (potentially) unsightly pipes and your existing radiators will be accustomed to the water pressure.

Pros:

• Great for low-pressure areas: The water pressure is gravity-fed from the loft tanks.
• Backup hot water: If the boiler breaks, the cylinder's immersion heater still provides hot water.
• Cost-effective replacement: Easy to install if replacing an older, identical system.

Cons:

• Requires space: You need a loft for the tanks and an airing cupboard for the cylinder.
• No instant hot water: Once the cylinder empties, you must wait for more to heat up.
• Less efficient: Stored hot water gradually loses heat over time.

3. System Boilers

A system boiler is the middle ground between a combi and regular boiler. 

It takes water directly from the mains but stores it in a hot water cylinder.

They’re more compact than conventional boilers, with a water cylinder but no water tank. 

So, if you are interested in a loft conversion, this might be better for you than a conventional boiler.

They’re also able to provide hot water to multiple taps at once while retaining pressure (where combi boilers can’t).

However, unlike with a combi, hot water isn't instant and it can run out.

Pros

• High pressure: It can supply hot water to multiple bathrooms simultaneously.
• No loft tanks: It is much more compact than a conventional system.
• Eco-friendly: The cylinder is often compatible with solar energy sources.

Cons

• Takes up living space: You still need room for the hot water cylinder.
• Limited hot water: Like conventional boilers, the hot water can eventually run out.
• Heat loss: Stored hot water will slowly lose heat over time.

What about Condensing Boilers?

Condensing boilers are not a separate boiler type.

In fact, all modern boilers are condensing boilers. 

'Condensing' simply means they are designed to capture and reuse escaping heat for energy-efficiency.

How boiler cover can help

Boilers can stop working for any number of reasons. 

Without boiler cover, you could end up paying a fortune for a relatively small repair.

At YourRepair today, we offer comprehensive boiler and home care plans that keep you in control.