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System Boilers Prices

System boiler prices vary between £470 and £2,600, depending on the make and model you choose to have installed.

If you’re thinking about getting a new system boiler for your home, you can expect to pay anything from £470 to £2,600. The cost of a boiler replacement depends on the size you require and the make and model you choose, plus you have to add on installation costs.

With so many different boilers on the market today, looking around for a new one can seem daunting and overwhelming. The key is to make sure you choose a boiler type and size that meets your heating and hot water demands. 

But no need to fret. We explain everything you should know about system boilers and their prices to help you select a boiler that suits your current and future needs.

What Is A System Boiler?

Unlike a combi boiler that heats water on demand, a system boiler needs a separate cylinder for storing hot water. Most people keep the cylinder in an airing cupboard. 

System boilers are ideal for homes with more than one bathroom and high heating and hot water demands. So, if you often have multiple showers, taps and radiators in use at once, a system boiler could be the best option for your home. 

How Does A System Boiler Work?

A system boiler takes water directly from the mains water supply, meaning you don’t need to have a tank in the loft as you would with a heat-only boiler. But if you want to have a system boiler installed, you will need an external cylinder to store your hot water.  

So, the two main components of a system boiler are the boiler and the hot water storage cylinder. Cold water travels from the mains to a system boiler which contains a heat exchanger that heats the water. Once the water heats up, the boiler sends hot water to either the radiators in your home or your storage cylinder, where it will stay until you need hot water. That means hot water isn’t instant, and you have to program your boiler to heat the water in advance or set a timer. 

The size of your cylinder dictates how much hot water you can use. When you run out of hot water, you have to wait for the cylinder to heat more water before you can use it again. 

How Much Does A System Boiler Cost?

It depends on the make and model you choose and the boiler size/output you require. You can find cheaper models that start at £470 or pay anything up to £2,600 for a high-end brand with a generous warranty. 

The table below lets you compare a range of system boilers from different brands and includes their size, warranty and price.

Biasi Advance Plus System16kW5 years£469
Vokera Vision S System20kW7 years£691
Ideal Logic+ System15kW7 years£780
Glow-worm Energy System25kW7 years£810
Baxi 600 System 18kW7 years£945
Viessmann Vitodens 100-W System30kW5 years£1,044
Vaillant ecoFIT Pure System25kW2 years£1,050
Worcester Bosch Greenstar 4000 System 24kW5 years£1,120

How Much Does A System Boiler Cost To Install?

System boiler installation costs vary depending on where you live, the amount of work involved and the installer’s hourly rate. If you want to replace a system boiler with a new one in the same location and don’t need a new cylinder, it will cost less than replacing a combi boiler with a new system boiler. 

The installation cost, including the boiler, a cylinder, a system clean and labour, can be anything from £1,400 to £6,950 (excluding VAT). 

Top-Rated System Boilers By Brand

The tables below show some of the system boilers on offer from the top-rated boiler brands. According to a recent survey by Which?, these are the top three boiler brands and the top three cheap boiler brands. 

Worcester BoschGreenstar 8000 Life System30kW or 35kW£1,230 – £1,37584%
ViessmannVitodens 200-W System19kW, 26kW, 30kW or 35kW£1,191 – £1,44481%
VaillantecoTEC Plus System12kW, 15kW, 18kW, 24kW, 30kW or 37kW£730 – £1,37076%
Baxi800 System18kW or 24kW£900 – £95076%
IdealLogic Max System15kW, 18kW, 24kW or 34kW£860 – £1,15074%
Glow-wormUltimate3 System25kW£81071%

What Size System Boiler Is Best For My Home?

We cannot advise you on the correct system boiler size for your home without knowing your heating and hot water needs. The general rule is the higher your heating and hot water demand, the higher the output you need. Other factors that affect boiler size include the number of bedrooms, bathrooms and radiators you have. 

The below table is a rough guide on what size system boiler may suit your home and needs. 

1-2Up to 1019kW – 18kW
3-410+2-318kW – 26kW
5+20+4+27kW – 40kW

Choosing the correct size system boiler is extremely important and can be bewildering, so we recommend you consult with a qualified heating engineer before making a decision. 

What Size Hot Water Storage Cylinder Will I Need?

In addition to choosing the correct size/output system boiler, you must make sure your cylinder can accommodate your usual hot water usage. 

If your cylinder is too small, it won’t meet your needs, and you’ll often run out of hot water and have to wait for more to heat up before enjoying a bath or shower. And if your cylinder is too big, you’ll end up storing more hot water than you need and waste energy and money. 

Hot water cylinders are available in a range of sizes. The general rule is to allow around fifty litres of stored hot water for every person per day. When working out the correct size cylinder for your home, you also need to look at the number of bedrooms, bathrooms and showers you have. However, we all use different amounts of hot water, and there is no one-size-fits-all solution.

If you’re unsure what size hot water storage cylinder you need, you should get a qualified heating engineer to visit you in your home and make a recommendation. Ending up with a too big or small cylinder will create issues or even cost you more money than is necessary. 

Advantages Of A System Boiler

Before replacing your boiler, you should consider the advantages of all boiler types. One of the main benefits of having a system boiler installed is that it can provide hot water to more than one tap, bath or shower at a time, making them perfect for medium and large-sized homes with multiple bathrooms. 

Other advantages include:

  • The cylinder stores plenty of hot water for when you need it
  • No need for a cold water tank in the loft
  • Several people can use hot water at the same time
  • Easy to install and use
  • Compatible with solar thermal systems
  • Compatible with heating controls

Disadvantages Of A System Boiler

Now that you know the advantages of a gas system boiler, you need to consider the cons of this type of heating and hot water system. Also, remember that a system boiler isn’t always suitable for smaller homes because it requires more space than a combi boiler. However, a system boiler needs less space than a heat-only boiler.

The disadvantages of a system boiler include:

  • You can run out of hot water
  • You may have to wait for the water to heat up before using more
  • You will need to use a programmer to preheat the water
  • You need space to store the hot water cylinder

Is A System Boiler The Same As A Combi Boiler?

No. Combi boilers take water directly from the mains and heat water on demand, whereas system boilers heat water in a storage cylinder. So, if you choose to have a combi boiler installed, you never have to wait for hot water because it can provide an unlimited supply. Another difference is that combi boilers take up less space than system boilers because they don’t require a separate hot water storage cylinder.

But there are disadvantages of combi boilers to consider as well. Although combi boilers heat water on demand, they can’t be installed with power showers and struggle to send hot water to more than one tap at a time, which can cause issues in homes with multiple bathrooms. 

Is A System Boiler The Same As A Heat-Only Boiler

No, system boilers are not the same as heat-only boilers. Also known as regular, traditional or conventional boilers, heat-only boilers work similarly to system boilers and need a hot water storage cylinder but also require a cold water tank, usually kept in the loft. 

Heat-only boilers are generally only suited to homes that already have a heat-only boiler and an older radiator system. 

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