System boiler installers · Gas Safe registered
Get a fixed-price quote online for a new system boiler and hot water cylinder, fitted by a Gas Safe registered engineer on a date you choose. Built for homes with more than one bathroom, system boiler installations with a cylinder start from £2,995 fitted.
Replacing a system boiler
A system boiler heats your radiators and a separate hot water cylinder. The pump and expansion vessel are built into the boiler, and with an unvented cylinder the stored water comes out at mains pressure, so a shower upstairs and a tap downstairs can run at the same time without either one dropping off.
That makes a system boiler the usual choice for homes with two or more bathrooms, larger families and households where everyone needs hot water at the same time each morning. Unlike a traditional regular boiler, there are no cold water tanks in the loft.
Replacing a system boiler can be a simple boiler-only swap if your cylinder is in good shape, or a full upgrade with a new unvented cylinder. Smaller homes with one bathroom may be better off with a combi boiler. New to the set-up? Read what a system boiler is, or see all our options for boiler replacement.
What you pay for a new system boiler depends mainly on the cylinder. If your existing cylinder is sound, a boiler-only swap keeps the cost down. Fitting a new unvented cylinder, converting from a regular boiler with loft tanks or switching from a combi adds parts and time. A new system boiler with cylinder starts from £2,995 fitted, and every online quote is fixed. For a wider look at what drives the price, see our guide to system boiler costs.
| Installation type | What’s involved | Price from | Time on site |
|---|---|---|---|
| System boiler with cylinder | New system boiler and a new or replacement unvented cylinder, suited to homes with multiple bathrooms | £2,995 | 1–2 days |
| Like-for-like system boiler swap | Replace the boiler only, keeping a cylinder that is in good condition, with new filter, flue and controls | Quoted online | 1 day |
| Regular to system conversion | Remove the loft tanks, fit an unvented cylinder and convert to a sealed, pressurised system | Quoted online | 1–2 days |
| Combi to system boiler | Add a cylinder and new pipework where a growing household has outgrown its combi | Quoted online | 2+ days |
System boiler finance: as an example, a £2,995 system boiler and cylinder spread over 10 years at 9.9% APR works out at £38.72 a month. Shorter terms, interest-free and buy now, pay later options are also available, subject to status. See our boiler finance options for the full details.
With a system boiler, the cylinder and the pressure in your pipework matter as much as the boiler itself. Our engineers check these on every job.
We check the age, insulation and coil of your existing cylinder. If it is sound we keep it; if not, we price a replacement into your quote.
An unvented cylinder is only as good as the mains feeding it. We measure pressure and flow so we know it will deliver strong showers across the house.
Unvented cylinders need a safety discharge pipe run to a safe point. G3-qualified engineers fit and test the valves, tundish and discharge to regulations.
Converting from loft tanks pressurises your system. We check older joints and radiators can take it, then flush and treat the system before the new boiler goes on.
The boiler’s built-in expansion vessel suits most systems. On larger systems with lots of radiators, we add extra capacity where it is needed.
We fit programmable controls for heating and hot water, so the cylinder heats when you need it, and can zone upstairs and downstairs in larger homes.
System boilers suit homes where several people want hot water at once. Here is what we weigh up with you.
Stored hot water can feed several showers at once, so system boilers suit family homes with en-suites. See do I need a system boiler for a 5-bedroom house.
As a rough guide, around 150 litres suits a smaller household, 210 litres a family with two bathrooms and 250–300 litres larger homes. Our hot water cylinder guide covers the options.
With a sealed system the loft tanks go, and with them the risk of a frozen or leaking tank in winter.
You will need a cupboard for the cylinder, usually where an airing cupboard already sits. If space is tight, a combi or storage combi may suit better.
Most cylinders include an electric immersion heater, so you still have hot water if the boiler is ever out of action.
A cylinder works with a solar PV diverter to heat water from surplus solar power, and heat pumps need one too, so it keeps your options open.
Fill out our simple online enquiry form. We just need a few details about your home to give you quotes for new boilers online.
Select a system boiler that fits your specific needs. You have the option to pay up-front, or with instalments on finance.
Next you will be able to choose a convenient boiler installation date. One of our Gas Safe registered engineers will complete installation of your new boiler.
You can choose from one of our boiler servicing plans, giving you peace of mind and keeping your boiler running smoothly for years to come.
Larger family homes and extended houses are where system boilers earn their keep. We fit them across our service areas, including York, Harrogate, Wakefield, Huddersfield, Leicester and Nottingham. Off the gas grid? See oil boiler installation and LPG boiler installation. See all our service areas.
A new system boiler with an unvented cylinder starts from £2,995 fitted. If your existing cylinder is in good condition, a boiler-only swap costs less and is quoted online. Your quote is fixed, so the price you see is the price you pay.
A boiler-only swap usually takes a day. Jobs with a new cylinder or a conversion from loft tanks usually take one to two days.
Not always. If your cylinder is in good condition, well insulated and compatible with the new boiler, we can keep it. Older or uninsulated copper cylinders are usually worth replacing at the same time.
A combi heats water on demand with no storage. A system boiler heats a cylinder of stored water, so it can supply several taps and showers at once. Combis suit smaller homes; system boilers suit busier ones.
Yes. We remove the cold water and feed-and-expansion tanks from the loft, fit an unvented cylinder and convert your heating to a sealed system, after checking your pipework and mains supply can handle the pressure.
Yes. Manufacturers recommend an annual check of the cylinder’s safety valves and expansion vessel, which can usually be done alongside your boiler service.
A Gas Safe registered engineer, who also holds the G3 qualification when an unvented cylinder is being fitted. Because we use subcontracted engineers, we check each one is qualified for the job before work begins. They commission the boiler, register the warranty and notify Building Control.
Yes. As an example, a £2,995 system boiler and cylinder over 10 years at 9.9% APR works out at £38.72 a month. Interest-free and buy now, pay later options are also available, subject to status.
Tell us about your home and hot water use, see fixed-price system boilers and book the installation date that suits you – all online, in a few minutes.