Combi Boiler vs System Boiler with Cylinder: Which is Right for Your Home?

When it comes to heating your home and hot water, the choice of boiler system matters. At Gas-Go Heating, we’re often asked:
“Should I install a combi boiler or a system boiler with a cylinder?”

Both systems have their pros and cons, and the best option depends on your home size, lifestyle, and hot water needs.

Here’s a clear comparison to help you make the right decision.

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🔧 What Is a Combi Boiler?

A combi boiler (short for combination boiler) is a single, compact unit that provides both central heating and hot water on demand, without the need for a separate hot water cylinder or cold water tank.

✅ Pros:

• Space-saving – No tanks or cylinders required
• Instant hot water – Heats water as you use it
• Energy-efficient – No stored hot water means less heat loss
• Lower installation cost – Fewer parts, simpler setup

❌ Cons:

• Water pressure can drop if multiple taps/showers are used at once
• Not ideal for large households with high hot water demand
• Relies on mains pressure – so not suitable in all areas

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🔄 What Is a System Boiler with Cylinder?

A system boiler works with a separate hot water cylinder to store heated water for use around the home. It doesn't require a loft tank (unlike conventional boilers) but still needs space for the cylinder, usually in an airing cupboard.

✅ Pros:

• Great for homes with multiple bathrooms
• Strong water pressure at multiple outlets simultaneously
• Can work with solar hot water systems for extra energy savings
• Ideal for families or properties with high hot water usage

❌ Cons:

• Requires more space for the cylinder
• Hot water isn’t instant – once the cylinder is empty, it needs reheating
• Slightly higher installation and maintenance costs

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🏠 Which Boiler Is Best for Your Home?