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System Boiler Costs & Quotes - 2021 Guide

system boiler costs guide for 2021

So what are system boilers?

A system boiler is the most compact way of increasing your hot water without compromising on comfort. While it can be close to impossible to deliver a large volume of hot water from a conventional mains-fed boiler, these compact models can do so with ease. Because they’re only designed for delivery and storage of hot water, they use up less space and are therefore cheaper to install and run. However, while they work like a regular boiler in that they store hot water in a cylinder, their design makes them much more convenient and flexible when compared to standard models.

System boilers have become popular in recent years with people looking for a more efficient, lower cost way of heating their homes. Although many condensing boilers can now deliver two thirds of their heat as hot water rather than unpleasant steam, they still produce up to a third of the energy they use in the form of unwanted heat. A system boiler on the other hand heats just enough hot water to meet consumer needs directly though the heating system and there’s no need to waste or make provisions for heat which is not required. This results in a much lower running cost (just 5-10% of total energy consumption depending on volume used) and an increased efficiency rating (as there’s no need for storage).

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How exactly does a system boiler work?

The system boiler is a type of boiler that has all the components necessary to generate both hot water and heat connected inside the hot water cylinder. This boiler is more expensive than other kinds, but it still has many benefits.

A system boiler does everything a regular boiler does – only it does it via your central heating system. By taking their water supply directly from the mains, system boilers eliminate the need for a tank of water in the loft, which would be needed with a regular boiler. They then heat the water to warm up the central heating as well as hot water for a cylinder. With this in mind, we’ve taken an in-depth look at them to see whether they really are worth investing in.

What are the differences between a combi and system boiler?

The system and combi boilers are the two main types of boiler you’re likely to find in the home. They both distribute hot water via underfloor heating or radiators, but there are some significant differences. Read on to find out what those differences are and which one is right for your home.

Combi boilers provide both hot water for your radiators and central heating for your underfloor system at the same time. For this reason, a combi boiler can be thought of as a hybrid of a standard central heating boiler and a cylinder-based hot water storage system, such as a system boiler. A combi boiler generates hot water on demand, because it does not require a water storage cylinder. As a result, the water in a combi boiler is constantly being recirculated and re-heated, so you have to use a different system to store your hot water.

A system boiler is an independently fired condensing boiler, when compared to the combi boiler which is part of a heating and hot water system. The main difference between the two boilers is domestic hot water capacity and heat output.

The main difference is in the volume of hot water each can deliver. A system boiler keeps a store of hot water on standby in its storage cylinder, but a combi boiler requires water to be drawn from a mains or tank circulating supply.

What are the differences between a regular and system boiler?

Have you ever wondered what the difference between a system boiler and a regular boiler is? There are so many options out there when it comes to your heating and hot water systems. You don’t just have to choose between a system and regular boiler, you can also go for hybrid boilers, underfloor heating, solar panels…the list goes on.

A conventional boiler is a less efficient, less energy-saving alternative to today’s system and combi boilers. While it’s probably true that older properties won’t be upgraded to more modern installations, many installers could potentially use these terms interchangeably. A good rule of thumb for domestic consumers is that if you have a water connection in your loft, then you have a system or combi boiler; if not it is most likely that you have a regular boiler.

Regular boilers run at a higher pressure than system or combi boilers. This can be fine for some homes but could cause major plumbing problems if the boiler is connected wrong or leaks at its connections.

All system and combi boilers will take their water from the mains supply, while regular boilers do not. This means that there are two tanks that need to be installed in your loft, known as the feed and expansion, or return, tanks.

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Is a system boiler the right choice for you?

While they’re not a new product, system boilers have emerged as the best combination of both combi and instant systems. The way they work is simple: the mains water goes into the indoor unit, which keeps some hot in case it’s needed; then stored in a smaller and more efficient cylinder (as opposed to a tank) for higher demand—this means you can have constant hot water on tap from multiple sinks. You can control it via remote or an app and get notifications if there’s a problem. Basically, they’re an easy way to bring the comforts of a big system without the headache of installation.

What are the benefits?

There are several advantages to installing a system boiler including convenience, reduced costs, and efficiency. Here are a few explanations of noteworthy advantages:

  • Instant high demand hot water: System boilers, also known as “storage hot water generators” (SWHs), are central heating systems that use a tank of stored hot water to heat your taps. This means that unlike a conventional boiler system, which uses gas to heat the cold incoming water entering the appliance, system boilers use stored water to provide instant hot water at all of your taps.
  • Economical: By including a pump with every system, the boilers respond faster and therefore more efficiently. This means you save money in heating maintenance costs. No more long waits for your boiler to warm up. With a system boiler you can get hot water with no delay.
  • Increased water pressure: System boilers rely on the water pressure of the mains supply rather than gravity, meaning that households can benefit from water pressure that’s up to four times higher than a traditional system.
  • Easy to install: When installing conventional boilers, a lot of piping work is required to connect the wide range of components. In effect a lot of extra effort and money is spent on pipework and the time-consuming task of pipe-laying. With a system boiler, all the components are easily accessed and installed within minutes, so you can be sure your system boiler will be installed quicker.
  • Solar energy compatible: Using a solar thermal system is a subtle but worthwhile way of generating hot water. By implanting an array of solar panels on your roof you can heat water using the natural energy that's available to us all. Since you'll be using your own source of energy there's no need for expensive gas or electric heating.
  • Cold water feed tank not necessary: No need for a cold water feed tank as system boilers do not require one. Using pressurised cylinders can save space, while still giving you the option of having a system boiler even if you don’t have a loft or store room available to place the expansion and feed tanks.

What are the disadvantages?

There are plenty of reasons to install a system boiler. But, before you make your decision to have one installed, it’s worth examining the potential cons as well. Here are some of the primary cons to installing a system boiler:

  • Cylinder size: Do you know how much hot water you will need? To calculate the amount of hot water that will be required, it helps to first know how many people you need to supply for. This will dictate the size of the cylinder or tank that is required. Based on a basic calculation, the average person uses between 40 and 50 litres of hot water each day. However, there are other factors that need to be taken into account before you can determine the exact size of cylinder or tank you will need including peak periods where more hot water is used and if you use showers or power showers as these tend to use more water.
  • Larger units: Although the space is minimal, it’s still more than a combi boiler requires. However, system boilers only take up half as much space as regular boilers do. The reason for this is the need for a hot water tank.

System boiler features to look out for

All system boilers are not created equal. If you’re looking to buy your own boiler or considering if you should have a new boiler installed, here are some features to consider when contrasting different models.

  • Efficiency rating: The efficiency of a boiler is the percentage of energy in its fuel that it can convert to usable heat. This is expressed as a rating out of 100%. It is an easy-to-understand way to judge how much fuel you will need to use, and how much of that will eventually turn into usable heat energy.
  • Output rating: The system boiler size or output rating you need will depend on the number of radiators and hot water cylinders. A typical small property will require a boiler with an output of between 25-50kW. The size of the boiler also depends on how much space is available to accommodate it, so it’s always best to seek advice before you buy.
  • Smart controls: Heating controls have come a long way in the last few years, with many boilers now offering smart heating. This technology can encompass many different features but the main benefit is to give you greater control over your home heating system.
  • Manufacturers Warranty: All boilers come with a manufacturer’s warranty, which covers the boiler should it develop a fault even after installation. The length of time covered and the extent of what is covered will differ depending on the type of boiler you choose.
  • Customer ratings: Customer reviews are a great place to start when it comes to choosing the best boiler for your needs. With so many different makes and models of boilers out there, it’s important that you take the time to read through what homeowners have to say about each model before making your purchase.
  • Expert opinions: It’s always a good idea to talk to experts. When it comes to boilers, heating engineers are the experts. They’ll give you a detailed walk-through of the system that meets your unique needs, as well as how the boiler works and what it can do for you.
  • Total cost: The price of a system boiler can vary greatly. System boilers for a medium-sized home priced between £500 and £2,000 before installation or cylinder costs. With so many options at your disposal, you’ll have no trouble finding a system boiler at the right price.

What size boiler does your home require?

The system boiler capacity refers to the power output of the unit, and is commonly measured in kilowatts (kW). So what size system boiler do you need? A rough formula is that 20kW is needed per house, plus an additional 10% if there are multiple bathrooms. This means that if you have a 150m2 house with a family of five living in it, you’ll need about a 35kW boiler. In addition to this power rating of 35kW, your boiler should also have a heat recovery rating of at least 90%.

Your home’s heating system needs to match the size and capacity of your home. A boiler that’s too small for your property could struggle to heat it up through the cold winter months – leaving you shivering and cursing up a storm. A boiler that’s too big, on the other hand, will kick out excess heat just because it can – eating up cash and making your energy bills soar.

To decide on the size of system boiler you need, we can work out the number of kilowatts your heating system needs to produce. The best way is to add up all the hot water consumption and heating requirements (in kilowatts), but this is only possible if you know what all the fixtures are in your home. This table will give you approximate figures for common domestic systems.

Number of Radiators System Boiler (Minimum kW)
6 (6 x 1.5kW + 3kW) 12kW
8 (8 x 1.5kW + 3kW) 15kW
12 (12 x 1.5kW + 3kW) 21kW
15 (15 x 1.5kW + 3kW) 26kW
20 (20 x 1.5kW + 3kW) 33kW

If you live in a smaller property with one bathroom and little space to spare for a cylinder combi boilers would be the most efficient choice. They are compact and highly energy efficient, using 80% less gas than conventional storage systems, so they’re much easier on your pocket.

Hot water - what size cylinder?

There’s no cut and dried answer to this question. You need to consider a whole host or factors when determining what size hot water cylinder you’ll require. What does the hot water demand of your property look like? How often does your hot water system run? What is the daily hot water demand? Are there any features you wish to incorporate into your system, such as a shower or spa? These questions will help determine size and brand of hot water system required for installation. It’s important to think about and consider all these things before deciding on which model to install in order to get the best outcome.

Which cylinder is best... vented or unvented?

If you were to ask anyone 10 years ago what the best cylinder type was, they'd almost always tell you it's a vented cylinder. But things have changed and unvented cylinders have been taking over from less reliable vented cylinders.

An unvented cylinder is like any other water storage tank...well, that's not strictly true. It's actually more akin to a mains water supply, with just a single pipe taking the water directly from the mains. In that sense, it's more of an 'unvented cistern' and can deliver higher flow rates with lower risk of contamination than its non-unvented cousins.An unvented cylinder is like any other water storage tank...well, that's not strictly true. It's actually more akin to a mains water supply, with just a single pipe taking the water directly from the mains. In that sense, it's more of an 'unvented cistern' and can deliver higher flow rates with lower risk of contamination than its non-unvented cousins.

Direct or indirect heated water?

There are two different types of domestic hot water storage systems. Direct and indirect cylinders. Simply put these cylinders act as a storage facility for hot water. So what is the difference between the two?

So the difference between an indirect and direct cylinder is simple, really. An indirect heater has a heat exchanger component that connects to your radiators; it then disperses the heat through your system’s radiators. A direct heater has a flue that rises to the top of the property and doesn’t rely on a separate heat exchange for dispersing heat. When having a system boiler installed, an indirect cylinder will be needed.

Optimum cylinder capacity for your home

The hot water cylinder capacity you require depends on a number of factors, including your family size and how many bathrooms are in your home. For example if you have a large family and 3 or 4 bathrooms then you may need a high-end hot water cylinder with a very high capacity.

Taking all this into account, it makes sense to determine your hot water demands and then decide what size cylinder best suits you. One way to do this is by measuring your family’s daily water usage over a number of days and then averaging the results. This will give you the daily litres of hot water your family requires. Then, based on the capacity of cylinders available, it’s simply a matter of choosing the one that best matches your family’s daily hot water needs.

Property Size Bathrooms Cylinder Size
1 Bedroom 1 120-150L
2 Bedrooms 1 150 - 180L
3 Bedrooms 1- 2 180 - 210L
4 Bedrooms 2 210 - 300L
5+ Bedrooms 2 300L+

In addition, if you’re planning to invest in solar thermal in the future (i.e. hot water cylinder), then the cylinder must be solar compatible . Meaning it can only be used with solar thermal and cannot be used with conventional gas or electric hot water systems.

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Model kW ErP Warranty Price
BAXI Megaflo 32 32
A Heat
7 £909.4
BAXI Megaflo 18 18
A Heat
7 £769.57
BAXI 800 824 24
A Heat
10 £911.5
BAXI 800 818 18
A Heat
10 £915.14
Ideal Logic Max 30kW 30
A Heat
10 £1074.27
Ideal Logic+ S24 24
A Heat
7 £995.92
Ideal Logic+ S30 30
A Heat
7 £1037.28
Ideal Logic Max 24kW 24
A Heat
10 £1038.13
Vaillant ecoTEC 627 exclusive Green iQ 27
A Heat
5 £1408.39
Vaillant ecoTEC Plus 624 24
A Heat
5 £1257.79
Vaillant ecoTEC Plus 615 15
A Heat
5 £991.39
Vaillant ecoFIT pure 630 30
A Heat
2 £1258.99
Vaillant ecoTEC Plus 618 18
A Heat
5 £1097.55
Vaillant ecoFIT pure 618 19
A Heat
2 £1013.5
Vaillant ecoTEC Plus 612 12
A Heat
5 £945.5
Vaillant ecoFIT pure 625 25
A Heat
2 £1200.16
Viessmann Vitodens 100-W 30kW 30
A Heat
A Water
5 £1210.78
Viessmann Vitodens 100-W 26kW 26
A Heat
A Water
5 £1140.22
Viessmann Vitodens 200-W 30kW 30
3 £1745.47
Viessmann Vitodens 200-W 25kW 25
3 £1653.57
Worcester Bosch Greenstar 27i 27
A Heat
7 £1055.9
Worcester Bosch Greenstar 8000 Style 35kW 34
A Heat
A Water
8 £1459.49
Worcester Bosch Greenstar 8000 Style 30kW 30
A Heat
A Water
8 £1459.37
Worcester Bosch Greenstar 21i 21
A Heat
7 £1025.62
Worcester Bosch Greenstar 9i 9
A Heat
7 £909.44
Worcester Bosch Greenstar 12i 12
A Heat
7 £896.41
Worcester Bosch Greenstar 15i 15
A Heat
7 £952.9

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