Which type of boiler is actually right for your home?
At some point, most homeowners face the boiler question.
This guide covers what each type actually does, how they differ in practice, and which is more likely to suit your home. No jargon, no hard sell.
How Much Does a New Boiler Cost?
Most UK homeowners can expect to pay somewhere between £2,000 and £4,500 for a new boiler installation, depending on the type of boiler, the complexity of the installation and the condition of the existing system.
Combi boiler installations tend to sit towards the lower end of that range, because the unit is self-contained and requires fewer additional components. System boiler installations, which involve a hot water cylinder alongside the boiler unit, are typically more involved and reflect that in the cost.
As with most things heating-related, the most accurate figure comes from an in-person assessment of your specific property.
Get in touch with our friendly team for a free quote tailored to your home.
What is a Combi Boiler?
A combination boiler provides both central heating and hot water from a single compact unit, without the need for a separate hot water cylinder or a cold water tank in the loft. When you turn on a hot tap, it heats water directly from the mains on demand. What you use, it heats.
That simplicity is a large part of the appeal. Fewer system components mean a quicker and often cheaper installation, less to go wrong, and no cupboard or loft space given over to tanks and cylinders.
Where a combi works well: Flats, smaller homes and properties with a single bathroom and modest hot water demand (larger combination boilers are on the market now that will accommodate houses with two bathrooms). If there is typically only one person showering at a time and the household is not large, a combi is likely to serve perfectly well.
Where a combi has limitations: Because it heats water as it is used rather than storing a supply, flow rate is limited by what the boiler can heat in real time. In a busy household where two showers might run simultaneously, pressure and temperature can drop. Combi boilers also rely on good mains water pressure, which can be a factor in some rural parts of Cornwall where incoming pressure may be low.
What is a System Boiler?
A system boiler works with a separate hot water cylinder, usually housed in an airing cupboard, to store a supply of heated water ready for use. Unlike older conventional boilers, system boilers have most components built into the unit itself, so there is no cold water tank needed in the loft. When you turn on a hot tap, you are drawing from the stored cylinder supply rather than asking the boiler to heat water on the spot. The key differentiator between a ‘regular boiler’ and a ‘system boiler’ is that the pump and expansion vessel are integral to the system boiler, this is a key factor if you need to run a pressurised heating system.
Where a system boiler works well: Larger homes with more than one bathroom, families with high hot water demand, and properties where several people are likely to want hot water at similar times. The stored supply means simultaneous use is handled comfortably. System boilers are also a much better fit for solar thermal panels, since the cylinder can be configured to take heat from the solar system, leaving the boiler to top up the temperature rather than do all the work.
And for homeowners thinking further ahead about renewable heating, a system boiler with a cylinder is a more natural staging post towards a heat pump than a combi. Our renewables team can advise on what makes sense for your situation.
Where a system boiler has limitations: The hot water cylinder takes up space. The stored hot water is also finite: if the cylinder is emptied, you have to wait for it to reheat, so correct sizing for your household’s actual usage matters.
It is worth a brief mention that a third boiler type exists: the conventional or regular boiler, which uses both a hot water cylinder and a cold water tank in the loft. It is most commonly found in older properties with heating systems designed around it. At Blue Flame we work with all three types across gas, oil, LPG and solid fuel systems, so if you have one and want to understand your replacement options, our engineers can advise on the right approach.
How the Costs Compare
Combi boiler installation typically runs from £2,000 to £3,500 for a straightforward replacement. System boiler installation, including the hot water cylinder, typically sits from £2,500 to £4,500 or more. Converting from one system type to another involves additional pipework work and usually sits at the higher end.
For customers where upfront cost is a consideration, we’re authorised and regulated by the Financial Conduct Authority and offer boiler installation payment plans through Novuna Personal Finance, allowing the cost to be spread into manageable monthly payments, subject to status and credit check.
What Affects the Cost of a Combi Boiler Installation?
Several factors influence the final price beyond the boiler unit itself.
Whether it is a like-for-like replacement matters considerably. Replacing a combi with a combi in the same location is the most straightforward and cost-effective scenario. Relocating a boiler within the property, or converting from a different system type, adds both time and cost.
The condition of the existing system also plays a role. Older systems often need flushing to remove sludge and debris before a new boiler is connected, and radiators or valves in poor condition may need attention to ensure the new boiler operates correctly and its warranty remains intact. Skipping this step is a false economy.
Adding modern controls, such as a smart thermostat, as part of the installation adds modest cost but improves efficiency and is generally worthwhile.
Efficiency: Does the Type Matter?
Both modern combi and system boilers are condensing boilers, a legal requirement for new domestic installations in the UK, and both achieve efficiency ratings above 90%.
In practice, the difference in efficiency comes down to how well the boiler type matches your household’s actual hot water demand. A well-matched boiler of either type will outperform a poorly matched one of the other. Getting the specification right is far more important than the type itself.
After Installation: Keeping Things Running
Whichever type you choose, annual servicing is the most reliable way to protect the investment. It maintains efficiency, keeps the manufacturer warranty valid, and catches developing faults before they become expensive ones.
Did we mention? Blue Flame’s membership plans include annual servicing as standard from Plus Membership upwards, alongside priority emergency call-outs with a guaranteed 24-hour response and unlimited call-outs. If something goes wrong between planned visits, our emergency repairs team is available 24 hours a day, 365 days a year.
Get a Free Quote from Blue Flame
Blue Flame has been installing boilers across Cornwall for over 30 years across gas, oil, LPG and solid fuel systems.
Every installation starts with a proper in-person survey, so you get the right boiler for your home, correctly sized and installed, backed by up to 12 years manufacturer warranty and our own 1-year no-quibble installation guarantee.
Call us on 01326 378122 or contact us online for a straight answer and a free, no-obligation quote.
Frequently Asked Questions
What is the main difference between a combi and a system boiler?
A combi heats water on demand directly from the mains, with no cylinder or tank needed. A system boiler stores hot water in a cylinder, allowing it to supply multiple outlets at once without losing pressure. The right choice depends on your property size, bathroom count and how your household uses hot water.
Is a combi boiler cheaper to install than a system boiler?
Generally, yes. A combi installation involves fewer components, which keeps the cost lower. System installations include a hot water cylinder, adding to both material and labour costs. That said, fitting the wrong boiler type to your home will cost more in the long run than getting the choice right from the start.
Can I use solar panels with a combi boiler?
Solar PV panels, which generate electricity, can sit alongside a combi set-up and reduce your wider energy costs. Solar thermal panels, which heat water directly, are generally not compatible with combi boilers because they require a hot water cylinder to store pre-heated water. If solar thermal is a consideration, a system boiler is the better fit. (as paragraph above)
Can I switch from one type to the other?
Yes, converting from combi to system means installing a cylinder and adapting the pipework. Going the other way means removing the cylinder. An in-person assessment is the best way to understand what is involved for your specific home.
How do I get an accurate quote for a combi boiler installation?
Because costs vary considerably between properties, the most reliable approach is an in-person visit. Contact Blue Flame on 01326 378122 or get in touch online and we will provide a clear, no-obligation quote tailored to your home.