The government’s drive to reduce the UK’s carbon footprint has prompted millions of householders across Britain to upgrade their central heating systems ahead of the 2025 ban on gas and oil being fitted into new build homes as their source of heat and hot water.
System boilers are best suited to large households with two bathrooms and sufficient storage space to accommodate a hot water tank or cylinder. The main advantage of upgrading your old heating system is that modern boilers are much more energy-efficient than old boilers and can save hundreds of pounds on your heating bill – according to estimates published by The Energy Savings Trust, detached homes can save as much as £305 a year.
System boilers are ideal for larger homes and properties that use large quantities of water. Other than being more cost-effective to run than conventional boilers, they also take up less space, as they have heating components built into the unit and do not require a cold water storage tank.
In this article, we’ll be looking into how much it costs to install a system boiler, what affects the cost of installing a system boiler, how to save money on installing a system boiler, how to know if a system boiler is the right choice for your home and how to find and hire a professional to fit your system boiler.
If you’re wanting to ditch your old heating system and upgrade to a system boiler but aren’t sure what that entails, keep reading to find out all you need to know about this heating appliance.
Topics
How Much Does It Cost to Install a System Boiler?
Firstly, let’s take a look at some of the top manufacturers of system boilers and compare their estimated supply and labour costs.
| System Boiler Manufacturer | Power Output (kWh) | Estimated Supply Cost | Estimated Labour Cost | Total Estimated Cost |
|---|---|---|---|---|
| Worcester Bosch | 12.2 to 30 kW | £900 to £1,300 | £500 to £2,000 | £1,400 to £2,300 |
| Ideal | 15 to 30.3 kW | £1,000 to £1,400 | £500 to £2,000 | £1,500 to £3,400 |
| Baxi | 24 to 25.9 kW | £1,000 to £1,200 | £500 to £2,000 | £1,500 to £3,200 |
| Vaillant | 18.5 to 37.6 kW | £1,000 to £1,400 | £500 to £2,000 | £1,500 to £2,400 |
| Viessmann | 19 to 26 kW | £1,100 to £1,500 | £500 to £2,000 | £1,600 to £3,500 |
A system boiler from Worcester Bosch with a power output of 12.2 to 30 kW will come in at between £900 to £1,300 for the supply costs alone. You’ll then need to factor in the labour costs, which will be between £500 to £2,000, giving a total estimated cost of between £1,400 to £2,300.
Looking at manufacturer Ideal next, a system boiler with a power output of between 15 to 30.3 kW will come in at £1,000 to £1,400, with the same labour charges as before of £500 to £2,000. This will give you a total estimated cost of between £1,500 to £3,400.
Baxi’s system boiler appliances of between 24 to 25.9 kW in power output come in at £1,000 to £1,200. With £500 to £2,000 labour fees, the estimated overall cost for purchase and installation is between £1,500 to £3,200.
Vaillant is up next, with a system boiler of 18.5 to 37.6 kW power outputs available, costing between £1,000 to £1,400, equal to a total price (including labour costs of between £500 to £2,000) of £1,500 to £2,400.
Our last system boiler manufacturer is Viessmann, with 19 to 26 kW power outputs on offer, between £1,100 to £1,500 in supply cost. With £500 to £2,000 being spent on labour costs, the total anticipated spend for this manufacturer would be near £1,600 to £3,500.
What Affects the Cost of Installing a System Boiler?
The Size of Boiler You Need
Getting the right size boiler and power output for your home is an important part of the process. As a rough guide, take a look at the following:
12 to 15 kW – suitable for one to three bedrooms and one bathroom
18 to 24 kW – suitable for three to four bedrooms and one to two bathrooms
30 kW+ – suitable for four or more bedrooms and two or more bathrooms
If you are having a new system boiler installed in your home in replacement of your traditional/regular boiler, you will have to have to swap your copper hot water cylinder to a steel, pressurised hot water cylinder, which will take between two to three days to install.
If You Are Converting from a Different Type of Boiler
The most cost-effective boiler replacement job is switching a like-for-like appliance into the same spot where your old system used to be. This won’t require any pipework or flue work and will be the most time and cost-effective solution – however, this might not be possible for some households wanting to change their heating style or for those who need a substantially bigger boiler to cater for an extension, for example.
For boiler upgrades of the same type (for example combi for combi, or regular for regular) that are moved to a new location to free up space, these will take longer but be more straightforward than switching boiler type. For an installation like this, you should expect to add two to three more days to your installation timeline.
System Boiler v Condensing Boiler
System boilers and condensing boilers are similar in that they both supply water from the mains – however, there are significant differences between the two that you should be aware of if you’re considering choosing between the two.
Condensing boilers are best suited to small homes. The units are much smaller than system boilers so don’t take up as much space, and a combi-boiler is usually small enough to fit into a kitchen cupboard or under the stairs.
System boilers require a tank or cylinder, where the water will be held and heated. This allows for hot water on demand, but will take up more space than other boilers. The advantage is that multiple users can source hot water at the same time from a system boiler, whereas with a combi-boiler, a shower will lose power and heat if you run water from a tap.
Combi boilers also give priority to hot water, so you may find your radiators lose heat whilst the shower or bath is running. System boilers can maintain both the radiators and water without losing pressure.
System boilers have no prioritisation system for how the heat is distributed, however, they can run out of hot water if you use more than is stored in the tank.
If You Plan to Move the Position of Your Boiler
It typically costs between £250 and £500 to get your boiler position moved elsewhere in your home, but this cost can raise itself if there is a considerable amount of pipework or flue work to be done.
Boiler Accessories
As we alluded to above, you may wish to obscure the sight of your boiler – which is where some boiler accessories, such as casings or covers, come in. Additional to the boiler itself, you may also want a thermostat installed to control the heat of your home from multiple locations, all of which will add more figures to your overall bill.
How Can I Save Money on a System Boiler?
Use HouseholdQuotes to find quotes from trusted tradespeople who can install your system boiler efficiently and correctly, and potentially save you up to 40% on your project quote too.
A good way to save money on your system boiler is to make sure you’re buying the right size and power output for your home. As the power output increases, so does the price, so you need to be careful not to step into expensive territory without meaning to.
Look for cost-savvy alternatives to moving your boiler. Keeping your boiler position consistent is better for your budget, but if you really want something moved from a prominent position in the kitchen to somewhere more discreet like a utility room, you may want to factor in this extra cost.
Some smaller boiler units are compact enough to be housed inside a kitchen cabinet, so before opting for the move, see if you can have cabinetry built around the appliance to obscure it first instead of trying to move the whole unit.
Is a System Boiler the Best Choice for My Home?
Below, we’ve listed some of the main advantages and disadvantages associated with installing a system boiler in your home to help you decide if it’s the best choice for your home.
Advantages
| Advantages |
|---|
| Space-saving, freeing up kitchens by being located in garages or lofts instead |
| Instant access to hot water |
| Aquires water directly from the mains supply |
| Hot water available to several users at the same time |
| Easy to install and operate |
| Compatible with solar panel heating systems |
Disadvantages
| Disadvantages |
|---|
| Storage space needs to be large enough to accommodate for a hot water cylinder |
| Risk of running out of hot water |
| Risk in choosing too big boiler size and paying more than is necessary |
| Higher costs for changing heating system in the home |
What’s Involved in Installing a System Boiler?
While the cost of installing a system boiler may be higher than traditional heating systems, they can look to save you money on your energy bills in the long term, equating to around £200 per year.
For a home switching their traditional boiler or combi boiler to a system boiler, you’ll need an unvented cylinder installed as well so that your boiler can draw water directly from the mains for use in your heating system. If you’re moving from a vented system, you’ll need to remove the old cold water tank as this will be redundant with your new system.
Your Gas Safe engineer will need to rework the pipes to supply your new system boiler, while some flue work may also be involved if moving location around the home. If necessary, your boiler will then be cased in, or if small enough, hidden inside a kitchen cabinet to ensure a discreet fitting.
How Do I Find and Hire an Installer?
Using HouseholdQuotes to find and hire an installer for your new system boiler is a great way of reducing your online search time while keeping the hunt to just one web page instead of spread across many different tabs. What’s more, it can often help to save you up to 40% on your project’s bill.
Seeking out recommendations from friends, family and neighbours can also be a great way to get verified tradespeople, as you will be able to go off a recent and verbatim review. If this isn’t possible, using the Gas Safe register to find a suitable installer is a great way to go while ensuring they are of the right qualifications to install for you.
It’s important to note that some suppliers provide the boiler and installation and some only the boiler, so make sure you double-check this before buying your system as you may or may not need to find an installer, too.
Ensuring the Professional Is the Right Fit
If you’re going off a friend or family member’s recommendation, it’s important to still check that the tradesperson is competent in their abilities and qualified to do the job, being enrolled on the Gas Safe register. Having a boiler installed by someone who isn’t is not only dangerous but can invalidate warranties.
You should always seek out a written quote to ensure the price you are quoted is the price you end up paying at the end of the project, with no nasty hidden surprises. It’s also good to check that the trader has the right type of insurance to cover themselves and you in the event of any issues.
Where possible, seek out references from previous jobs to make sure they produce the kind of results you’re looking for and see what experience they have in terms of past jobs to ensure they’re a good fit for you. This can be especially important if you’re switching from one heating system to a new one, as this is a considerable amount of work compared to a straight swap.
Final Checklist
If you’re wanting to upgrade your heating system and think a system boiler is the way to go, make sure you take note of our final checklist to ensure everything is thought of both before and during the project.
- Choose the right size boiler and power output for your home using an online calculator
- Try to keep the boiler position the same to cut costs, or look into covers/casings to obscure the appliance instead of changing pipework
- Bleed radiators or flush the system to get everything working efficiently without the need to replace radiators at the same time
- Find a reputable tradesperson using HouseholdQuotes
- Make sure to get a written quote and check out the trader’s references and past experience before signing with them
Frequently Asked Questions
How Do System Boilers Work?
The only drawback of this setup is that hot water cylinders can only hold a certain amount of hot water at any one time. This can result in the loss of hot water when running a bath or taking a shower if a lot of water has been used over a short space of time, needing you to wait for the tank to fill back up again before resuming use.
Through comparison, when considering combi boilers, this isn’t an issue as there is no cylinder or water tank; rather the water is heated on demand and distributed within five seconds, leading to less water waste. This has its own pros and cons too, though, as combi boilers are responsible for both the central heating and hot water supply, meaning if your system goes down, you’re without both.
What Size Hot Water Cylinder Do I Need?
- Low consumption: 20 – 30 litres
- Average consumption: 30 – 50 litres
- High consumption: 50 – 70 litres
Showers typically use 18 litres of water per minute, while baths use 100 litres of hot water, which you can use to help guide your decision.
What’s the Difference Between a Vented and Unvented Cylinder?
The benefit of an unvented cylinder is that you don’t need an additional water tank in your home, which is great for those with less space.
Are System Boilers More Expensive Than Other Boilers?
The main difference is that system boilers only have one tank which is used to heat the hot water. Regular boilers, also known as heat-only boilers, need a second tank to store cold water.
Although regular boilers require more storage space, they have an advantage over system boilers in that they never run out of hot water. Heat-only boilers consistently source water from a cold water tank so that the hot water is always full.
On the other hand, system boilers save space and you don’t have the risk of cisterns fitted in the loft or garage freezing over when temperatures hit below zero.
Regular boilers are better suited to houses that have traditional heating systems installed, although they do take longer to fit than system boilers. Subsequently, the cost of installation and repair is typically higher than system boilers.
How Long Do System Boilers Last?
What Is a Sustainable Alternative for My Heating?
For more information on heat pumps, see our dedicated page.