Which type of boiler is best for my home?

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Combi boilers

Combi boilers are single units - typically small enough to be hung on a wall - which generate heat and hot water for an entire home. They don’t come with hot water storage tanks; instead they heats water on demand, creating instant hot water thanks to their heat exchangers.

These heat exchangers are made of metal - either aluminium or stainless steel - and they heat the water, which comes through the mains tap, by burning fossil fuels such as oil or gas, depending on the model. Some of the better combi boilers are also hydrogen-ready, making them more future proof as the UK moves away from fossil fuels.

Pros of combi boilers

• High energy efficiency
• Heats both the home and water, saving on energy bills
• Small, compact size will mean more space in your home after replacing your old boiler
• Instant hot water on demand means no waiting around for the shower to warm up
• Low maintenance costs

Cons of combi boilers 

• Not suited to properties with low water pressure or flow rates
• Not ideal for larger households with multiple hot water outlets i.e. showers, as flow rate is reduced when providing hot water to multiple units at once

System boilers

Unlike combi boilers, system boilers include a hot water cylinder, which is basically a tank used to store any hot water created for later use. 

They are more similar to regular heat only boilers, the main difference being that system boilers are unvented. This means they look a lot neater than heat only boilers, with all the components such as pumps as valves being located within the boiler itself, as opposed to outside of it. 

Pros of system boilers 

• Large water storage tank is ideal for larger homes with high hot water demands.
• All components are integrated into the boiler, meaning they take up less space than regular heat only boilers.
• Typically come with longer warranties than heat only boilers thanks to their superior build.

Cons of system boilers

• The need for a hot water cylinder means they require more space than a combi boiler.
• Hot water flow doesn’t work as well if the water pressure from the mains supply is low.

Heat only boilers

Otherwise known as ‘regular’ or ‘conventional’ boilers, heat only boilers provide hot water directly to radiators, or a cylinder for storage.

Unlike system boilers, heat only boilers usually have an ‘open-vented’ system. This also require a cold water storage tank, which is usually placed in an attic or loft, which then feeds water into the boiler for heating. So, you will naturally need more space in your home for this type of heating system. 

Pros of heat only boilers

• Usually the cheapest type of boiler, which also means they’re cheaper to repair and replace.
• Typically have a larger flow rate, making them better suited to large households with multiple bathrooms and high hot water demands.
• Better suited to homes with older heating systems and radiators due to the fact it doesn’t need a high-pressured water supply from the mains.
• Ideal for properties that struggle with low water pressure.

Cons of heat only boilers

• Less likely to be compatible with more modern heating systems and appliances, including solar panels and smart thermostats.
• You’ll typically have to wait longer for water to heat up compared to combi or system boilers.
• You’ll need more space at home, including attic space, to house both the cylinder and cold water tank. May not be suitable for smaller homes.
• Manufacturer’s warranty will typically only cover the boiler itself, meaning the cylinder, water tank, and any external pumps and valves won’t be covered should they break down.

So, which type of boiler is best for my household?

Which type of boiler you go for when upgrading your central heating system should, ultimately, depend on the type of property you live in. 

• Small to medium sized households with 1-2 bathrooms are best suited to combi boilers. For more info, check out our guide on the best combi boilers in 2022. 
• Larger households with 2 or more bathrooms and high demand for hot water will be better suited with a system boiler. If this sounds like you, take a look at the best system boilers in 2022. 
• Older homes with antiquated radiators, or those on a tight budget, will be better off with a heat-only boiler.