What Is a System Boiler? How It Works, Pros, Cons & Costs

Are you scratching your head over which boiler type will suit your home?

If you live in a larger household with high hot water demands, a system boiler could be the perfect fit.

Read on to find out:

• How they work
• The pros and cons
• Whether they are the right choice for your property.

Please note: The following article is aimed at helping you understand system boilers. It’s always advisable to leave boiler installation, diagnosis, and repair work to a professional Gas Safe registered engineer.

What system boilers are

A system boiler is a boiler system that includes a hot water cylinder for storage.

(By contrast, Combi boilers don’t require them.)

However, because components like the expansion vessel and pump are built directly into the boiler itself, they don’t require a cold water tank in the loft.

This makes them much more compact than conventional boilers, and they are a fantastic choice if you are planning a loft conversion.

How they work

A system boiler heats water and stores it in a hot water cylinder for later use.

Hot water is then pumped from the boiler into your home’s radiators.

This ensures a fast response time for your central heating while keeping running costs affordable.

Because the water is supplied from a storage cylinder, it maintains a constant pressure. So, you can enjoy high flow rates at mains pressure.

Modern system boilers are also condensing boilers, meaning they extract over 90% of the heat from the fuel they burn.

This involves extracting and recycling heat from flue gases, making them a highly cost-effective and energy-saving choice.

How to know if a system boiler is right for your home

1. Check your property size

System boilers are excellent for large, busy families.

They can easily heat homes with up to 7+ bedrooms and comfortably run hot water to several bathrooms at once.

2. Check your current layout

Look at the current layout of your central heating system.

If you have a boiler and a pressurised hot water cylinder (like a Megaflo) installed, but no loft-installed tank, your current boiler is already a system boiler.

For heating engineers, a like-for-like swap is generally much easier.

3. Check your hot water demand

Your household’s demand for hot water will dictate the size of the boiler you need.

Because the cylinder stores a set amount of water, you can determine exactly what output you will need to match your daily usage.

Advantages of system boilers

Multiple outlets

They can supply hot water to multiple taps and showers simultaneously without any drop in water pressure.

Space-saving

They take up far less room than regular boilers because there is no need for a cold water tank in the loft.

Solar compatibility

They can easily be used in conjunction with solar thermal systems to further reduce your carbon footprint and energy bills.

Easier maintenance

In-built components like the pump make installation and future maintenance much more straightforward.

Disadvantages of system boilers

Requires programming

System boilers only heat water ahead of time.

You will need to pre-program a timer to ensure you have hot water exactly when you need it.

Limited hot water

You are limited by the capacity of your cylinder.

If you run out, you must wait for the cylinder to fill and reheat before using hot water again.

More space than a combi

Unlike an all-in-one combi boiler, you still need to find extra space for a hot water cylinder.

You may also need to insulate this cylinder to stop heat and energy loss.

System boiler alternatives

Combi boilers

Combi boilers are an all-in-one, cost-effective home heating solution.

They don’t require any tanks or cylinders, which saves massive amounts of space.

However, they often struggle to produce enough hot water for larger families with multiple bathrooms.

Conventional boilers

Conventional boilers (also known as regular boilers) require both a hot water cylinder and a cold water tank.

They are best suited for homes with traditional heating systems already in place, but they take up the most space.

Expert boiler support from Hometree

Need boiler cover? Get in touch with Hometree.

If we can’t help you over the phone, we’ll send out one of our Gas Safe registered engineers to inspect and repair your boiler.