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ATAG iS System Boiler

The ATAG iS System comes in various outputs and is suitable for any size home.

According to ATAG, the iS System is one of the most energy-efficient boilers in Europe. It comes in a range of outputs to suit your heating and hot water needs but it does require a separate hot water cylinder, so you’ll need enough room in your home to store this. The boiler itself is compact and quiet in operation, plus you can purchase an even smaller model that’s 275mm deep to enable you to store your boiler in a kitchen cupboard.

How Much Does this Boiler Cost?

There are five models available in the ATAG iS System boiler range with outputs of 15kW, 18kW, 24kW, 32kW or 40kW. The cost of purchasing this boiler depends on which output you require but we do know that you need to spend between £1,270 and £1,510 including VAT and excluding installation fees. If you have a large home and high heating and hot water demand, you can expect to pay more as you’ll probably require one of the higher output models.

How will I know if this Boiler is Suitable for My Home?

Most of the components, such as the pump and controls, are contained within the boiler casing to ensure the ATAG iS System doesn’t take up too much space in your home. However, the boiler still needs to be fitted with a hot water cylinder to store your water until you need it, so it requires more space than a combi. On the plus side, the ATAG iS System is ideal for most property sizes and can handle high heating and hot water demand. Since there are five kW outputs available, you must figure out how powerful the boiler needs to be to meet the requirements of your household.

Don’t worry if you don’t know which ATAG iS System boiler model/output to choose. Instead of guessing and to avoid getting it wrong, just ask a local Gas Safe registered engineer to determine what size boiler you need.

Is it a High Efficiency Boiler?

The ATAG iS System is an Energy Saving Trust endorsed product as it achieves an A rating for heating and hot water efficiency and can help to save you money on your gas bills. It has an in-built ErP pump to control the heat given out by the boiler and to ensure the boiler is as energy-efficient as possible. What’s more, this boiler is compatible with solar hot water thermal systems and the ATAG OneZone smart controller, both of which can help to further reduce carbon emissions and save you even more money on your bills.

Does this Boiler have a Good Range of Controls and Features?

To be fair, it has pretty much everything you could want from a reliable and affordable system boiler. Not only does the ATAG iS System come with intuitive controls and an LCD display with detailed fault codes but it has a built-in anti-cycling function and a factory fitted ErP pump for low electrical consumption and improved efficiency. This boiler also has an ATAG iCon stainless steel heat exchanger with a lifetime guarantee and a combined condensate and pressure relief valve outlet pipe reduce the amount of pipework needed. The ATAG iS System can even be supplied with a fixing jig as standard for rear piping behind the boiler or as a 275mm deep model to enable you to get it installed inside a kitchen cupboard. 

How long is the Warranty on this Boiler?

All ATAG iS System boiler models come with a 10-year warranty as standard and the stainless steel heat exchanger has a lifetime guarantee. The warranty can be extended to 11 years with a filter only pack, 12 years with a water treatment pack or 14 years with a complete care pack. The complete care pack includes the OneZone smart controller, which lets you control the temperature in your home from a tablet or smartphone. 

Summary of Important Information

  • Expect to pay between £1,270 and £1,510
  • Heating output of 15kW, 18kW, 24kW, 32kW or 40kW
  • Dimensions of 700mm (H) x 440mm (W) x 355mm (D)
  • A 275mm deep model is available to fit inside a kitchen cupboard
  • Uses gas as its fuel source
  • A-rated for efficiency
  • Compatible with smart controls
  • 10-year warranty as standard

Pros and Cons

It’s hard to say anything negative about the ATAG iS System boiler as it has so many benefits and features, not to mention the generous standard warranty that can be increased from 10 to 11, 12 or 14 years. The only real disadvantage is that the boiler requires more space as it needs to be installed alongside a separate hot water storage cylinder.


  • Suited to small, medium and large-sized homes
  • Can handle high hot water demand with ease
  • Easy to install, use and service
  • Intuitive controls and LCD display
  • ATAG iCon stainless steel heat exchanger with a lifetime guarantee
  • Built-in anti-cycling function for improved efficiency
  • Factory fitted ErP pump for low electrical consumption and improved efficiency
  • Provides maximum energy efficiency – reduce fuel bills and carbon emissions
  • Compatible with the ATAG OneZone controller – improves efficiency and comfort
  • Compatible with ATAG iSteel cylinder range and solar thermal hot water systems
  • Excellent rating on Trustpilot – correct at time of writing in November 2020
  • 10-year warranty as standard
  • Warranty can be increased to 11, 12 or 14 years


  • Requires separate cylinder
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