Combi or System Boiler: Which Boiler Should You Pick?

Selecting the perfect boiler for your home is a significant decision. With energy efficiency, space considerations, and household needs in mind, choosing between a combi boiler and a system boiler requires careful thought. At Pleasant Plumbers, we specialise in professional boiler installations, including combi boiler installations and system boiler setups, ensuring you get the most efficient solution tailored to your home.

A combi boiler (short for combination boiler) is an all-in-one heating unit that provides both hot water and central heating without requiring a separate water tank. Since everything is contained in one compact unit, Pleasant Plumbers can install a combi boiler in homes with limited space, such as apartments or smaller houses.

Combi boilers heat water directly from the mains, meaning hot water is available on demand whenever you turn on a tap or switch on the heating. This design eliminates the need for a hot water cylinder, making it an excellent space-saving solution.

• Compact & space-saving – No need for a separate hot water cylinder.
• Hot water on demand – You’ll never run out of hot water.
• Faster installation – A single-unit system is easier and more cost-effective to install.
• Lower maintenance costs – Fewer parts mean fewer potential issues.
• Higher efficiency – Modern combi boilers are up to 92% efficient, reducing energy bills and CO2 emissions.
• Better water pressure – Takes water directly from the mains for stronger pressure.

• Limited hot water supply – Struggles with multiple taps or showers running simultaneously.
• Slight delay in hot water – Unlike a system boiler, there’s a short wait for the water to heat up.
• Dependent on mains pressure – If your home has low water pressure, a combi boiler may not be ideal.

A combi boiler is best suited for small to medium-sized homes with one or two bathrooms. If space is at a premium and your household doesn’t frequently require multiple hot water sources at the same time, this could be the perfect option.

A system boiler operates similarly to a combi boiler but requires a separate hot water cylinder to store heated water. This allows for a greater supply of hot water, making it suitable for larger homes where multiple taps or showers may be used simultaneously.

With a system boiler, water is drawn from the mains, heated via a heat exchanger, and stored in a cylinder until needed. This setup ensures instant hot water delivery but does require additional storage space.

• Can supply multiple outlets – Ideal for homes with several bathrooms.
• Excellent hot water pressure - Best for high pressured showers and excellent pressure to all hot water outlets as long as the incoming water mains supply is good.
• Instant hot water – Stored water means no waiting for heating.
• Compatible with solar heating – Can be integrated with solar panels for greater efficiency.
• Option for immersion heater – Can provide backup hot water if the boiler fails.
• Downsides of a System Boiler:
• Requires more space – Needs room for a hot water cylinder.
• Longer installation process – More components mean a more complex setup.
• Limited hot water supply – Once the cylinder is empty, it must be reheated before more hot water is available.
• Minimum incoming water pressure requirement - Minimum pressure of 1.5 bar required on the cold water mains inlet
• Higher maintenance potential – More parts mean higher repair costs.

If you live in a larger home with multiple bathrooms and higher hot water demand, a system boiler is the better option. It ensures you won’t run out of hot water even with several taps running at once.

The right boiler depends on your home’s size, space availability, and household needs. Before deciding, consider these factors:

• Current System – Replacing your existing boiler with the same type is often the most cost-effective option.
• Household Size – Combi boilers are best for smaller homes, while system boilers are ideal for larger properties with multiple bathrooms.
• Available Space – If you have limited space, a combi boiler is the better choice, as it doesn’t require a hot water cylinder.
• Water Pressure – With high mains water pressure will benefit from a system boiler and an unvented cylinder. Homes with adequate water pressure will More suited for combi boiler.

At Pleasant Plumbers, our Gas Safe engineers can assess your home’s heating needs and recommend the perfect solution.

A conventional boiler is similar to a system boiler but also requires a separate cold water storage tank, usually placed in the loft. This additional tank helps regulate water pressure and ensures a steady flow, even in areas with low mains pressure.

Conventional boilers are typically best for older homes with traditional pipework and radiators. They’re also suited to homes with higher ceilings that require a powerful heating system to maintain warmth.

Whether you need a combi boiler installation or a system boiler upgrade, our expert engineers at Pleasant Plumbers are here to help. We provide top-quality, energy-efficient boiler installations tailored to your home’s needs.