Looking for a 40kw system boiler and wondering which is the best on offer? Let's find out.
Thinking of purchasing a 40kW system boiler?
With so many options on the market, it can be a headache to find the right option for you.
However, in this guide, we’ve narrowed things down to what we consider the best choices out there.
It should be noted, though, that there are few system boilers with an output of exactly 40kW, so we’ve looked at system boilers with a capacity range of 35-44kW.
PS we fit new combi boilers with gas installation nationwide. Simply answer these questions, get your fixed price and you could get it installed as quick as tomorrow.
What is a 40kW System Boiler?
First and foremost, system boilers feature a separate water storage cylinder meaning that these boilers can provide a continuous supply of hot water for a property.
This contrasts with combi boilers which are only capable of heating water on demand. System boilers are well-suited to properties with a large demand for hot water and heating.
The capacity of system boilers is measured by kilowatts (kW). Considering you can find many system boilers with an output of around 15-30kW, system boilers with a 40kW output are an especially large capacity option.
40kW system boilers would suit large homes with about twenty radiators and two or more bathrooms.
If you were to go with, say a 35kW system boiler, it would be suited to a slightly lesser capacity.
Of course, the opposite is true for a system boiler with an output of 42.5kW or 44kW. These points are important to keep in mind when looking at the boilers discussed below, particularly if you had something particular in mind.
Best 35-40kW System Boilers
In this section, we’ll look at our favourite system boilers with an output of between 35kW and 42.5kW. We’ll discuss their features, qualities, warranties and price tag.
Each of the following system boilers is a gas boiler. If you’re looking for a high-end oil system boiler with a capacity of close to 40kW, consider the Firebird Envirogreen Systempac 44kW or Viessmann Vitodens 200-5 42kW.
But without further ado, let’s get to our favourite high output system gas boilers…
ATAG i40S
To start with we have the only boiler on our list with an output of exactly 40kW.
ATAG is a popular heating brand with a history of almost seven decades in designing and manufacturing boilers.
Not only that but they have a superb 4.8-star rating on Trustpilot from nearly 4,000 customer reviews.
Features, Qualities and Warranties
ATAG’s i40S is an exceptionally efficient boiler (with an energy efficiency rating of 94%) and a warranty of up to fourteen years.
The standard guarantee is ten years, but an additional four years can be added when you meet certain conditions.
The i40S system boiler features simple controls that offer a user-friendly experience. In addition, the boiler comes with an iCON heat exchanger with a lifetime guarantee. This boiler is compatible with ATAG’s iSteel hot water tanks.
Its dimensions stand at 440mm (W) x 700mm (H) x 355mm (D) making it a compact option. If you want a high output system boiler that won’t use up too much space, the ATAG i40S would be a great choice.
Installation Cost
The standalone cost of the ATAG i40S is about £1,500. With additional costs (such as that of labour), your final installation bill would be around £2,300 to £2,800.
Alpha E-Tec 38kW System Boiler
One of our favourite boiler brands out there is Alpha Boilers. In fact, we’ve ranked Alpha in second place in our list of the best boiler brands in 2022.
For their quality, this Italian heating brand offers relatively inexpensive boilers in general.
Features, Qualities and Warranties
The E-Tec is the most popular system boiler from Alpha; it’s available in two models with outputs of 28kW and 38kW each.
The Alpha E-Tec features a stainless-steel heat exchanger instead of aluminium.
You’d usually only see stainless steel versions offered from more expensive brands, reflecting the fact that despite being more of a budget brand (in price tag), Alpha is arguably a premium brand at heart.
Stainless-steel heat exchangers are generally more durable since they offer more heat- and corrosion resistance than their aluminium counterparts. If you purchase the E-Tec through Heatable you can avail of a solid ten-year warranty.
Another key feature of the Alpha E-Tec 38kW system boiler is that it features a zinc-plated expansion vessel to protect against corrosion.
Beyond that, it comes with an energy efficiency rating of 93%, dimensions of 440mm (W) x 712mm (H) x 255mm (D) and an easy access front panel (this makes it handy for an engineer to service). The E-Tec was Good Homes Magazine Approved in 2021.
Installation Cost
The supply price of the Alpha E-Tec 38kW model is about £1,000. To have this boiler installed would come with an overall bill of around £1,800 to £2,300. This is a great budget option for those seeking a boiler with a large capacity without breaking the bank. All in all, the E-Tec 38kW system boiler is great value for money.
Vaillant ecoTec Plus 637 System Boiler
Another brand is generally known for its affordability is Vaillant. While they are not quite to the standard as Alpha, Vaillant models are still a solid choice on the market.
Both Alpha and Vaillant have 4.6-star ratings on Trustpilot. However, we consider Vaillant the fifth-best boiler brand on the UK market, three places short of Alpha.
Features, Qualities and Warranties
This 37kW system boiler is a popular and compact Vaillant system boiler with dimensions of 440mm (W) x 720mm (H) x 406mm (D).
It’s easy to install and features high-quality modulation meaning that it can reduce its output when the heating demand is low (making it extra efficient and saving you on your heating bills).
The ecoTec Plus 637’s energy efficiency rating is 94%. One other standout feature of this boiler is that it comes with a flame light detection system.
This allows for quieter and more efficient combustion. The Vaillant ecoTec Plus 637 system boiler has a five-year guarantee as standard but this can be extended to seven years if a Vaillant Advance Installer fits it for you.
Installation Cost
The ecoTec Plus 637 system boiler would cost about £1,500 to £3,000 to purchase standalone.
The overall installation cost would probably bring your final bill to somewhere between £2,300 and £3,300.
While this is a solid option for a high output system boiler, it doesn’t quite offer the same value for money as the previous two products.
Viessmann Vitodens 100-W 35kW Gas System Boiler
In our opinion, Viessmann is the top dog in the boiler market.
The German heating and refrigeration manufacturer has won several Which? Best Buy Awards. Their boilers are also widely praised for both their durability and quality.
Features, Qualities and Warranties
The 100-W system boiler is offered in 25kW, 30kW and 35kW models. These boilers are well-suited for the 2020s as they feature built-in Wi-Fi, and they are hydrogen ready.
The dimensions of this boiler stand at 595mm (W) x 455mm (H) x 800mm (D). Its efficiency levels stand at 89.5%.
Despite this not being quite to the efficiency levels seen among other top high output system boilers, the 100-W 35kW model is high quality in more ways than one. For instance, it features a reliable Inox-Radial exchanger that features a MatriX cylinder burner.
This Viessmann boiler alike Vaillant’s ecoTec Plus 637 comes with modulation technology. With a ratio of 1:6, it can reduce its operating power by as much as a sixth when demand is lower.
This can reduce wear and tear (increasing the life expectancy of your boiler) and reduce your energy bills.
The Vitodens 100-W 35kW model also comes with a user-friendly LCD touchscreen which features an optional outdoor weather detector allowing the boiler to adjust temperatures based on outside conditions. The boiler also operates quietly due to its low fan speed.
Installation Cost
To buy this 35kW boiler, you’d need to budget for approximately £1,300 to £1,500. The overall price of installation would be about £2,100 to £2,800.
Intergas Compact HRE SB
Last but not least we have this relatively inexpensive system boiler from Intergas.
This Dutch heating brand has a solid range of boilers to choose from. The company also ranks sixth among the most highly rated boiler brands on Trustpilot.
Features, Qualities and Warranties
A big selling point of the Intergas Compact HRE SB (at least as part of this list) is that it has a superb 42.5kW output.
This system boiler also comes with just four moving parts which significantly lowers the risk of faults occurring.
Homeowners can also choose between vertical and horizontal flues providing flexibility when it comes to having this boiler installed.
The Compact HRE SB features a seven-year warranty as standard with a ten-year warranty on its heat exchanger.
Further, it comes with built-in boiler frost protection which is particularly useful if the boiler is being fitted in an attic or garage.
The protection ensures that the boiler keeps working as usual during the winter. The dimensions of this Intergas system boiler are 450mm (W) x 710mm (H) x 240mm (D).
Installation Cost
You can expect a standalone price for this boiler of around £1,100 with the total cost of installation being about £1,900 to £2,400.
Best 40kW System Boiler: Verdict
Today we’ve looked at five top-quality system boilers with high outputs of between 35kW and 42.5kW.
Determining the best option for you would really depend on what you’re looking for.
If you want a system boiler with an exact output of 40kW, go for the ATAG i40S. But when it comes to value for money, we’d recommend the Alpha E-Tec 38kW system boiler.
If money is no object, then Viessmann’s Vitodens 100-W 35kW model is arguably the best choice to go with, although its lower energy efficiency rating is one key drawback worth keeping in mind.
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