Green Central avatar

Written by

Last updated:

Vaillant EcoTEC Exclusive Green IQ 843 Combi Gas Boiler Review

Vaillant EcoTEC Exclusive Green IQ 843 Combi Gas Boiler Review

Vaillant EcoTEC 843 Exclusive Combi Green IQ 43kw

Welcome to Compare Boiler Quotes, the UK’s best source for boiler quotes, information, news, tips, and advice on everything boiler related. 

Our articles on the best and worst boiler systems are always being written and posted so chances are we have covered the boiler you’re looking for. Today’s review is on one of the most advanced and high-end boilers for the modern British home. 

Fill in our form for Vaillant boiler quotes:

Hot Deals Icon

Comparing the Vaillant ecoTEC Exclusive 843

Most of us are familiar with the German manufacturer Vaillant and their range. If you’re not, they are certainly in the top 5 combi boilers when it comes to quality and performance. 

We’re going to be looking at one of their premier systems, the efficiency, warranty, the price of the boilers, and overall conclusion on the system.

Let’s first take a short look at the company in case you haven’t heard of Vaillant.

Vaillant ecoTEC Exclusive 835 Green IQ 35kw

If you’re looking for the smaller brother in this range, have no fear, most of the review about the 43kw combi boiler also relates to the less powerful combi apart from the flow rate and output. They are both obviously super-efficient boilers designed to keep running costs down. 

Hot Deals Icon

About Vaillant

Vaillant Boiler Prices

Vaillant, is a part of the Vaillant Group and has been building boilers for over 100 years. They are one of the most respected boiler brands from the German boiler manufacturers. 

Vaillant has produced some of the most advanced and best-performing boilers in the world and the EcoTEC Exclusive Green IQ 843 is certainly proof of this.

Core ecoTEC Exclusive Features:

Vaillant EcoTEC Exclusive Green IQ 843 Combi Gas Boiler Review

The key feature here is Vaillant’s green IQ technology, which offers a unique range of smart technologies and features, all merging to create a highly efficient boiler. 

These advances in green technology intelligently manage consumption and output while keeping its components running at peak performance for longer. It also offers a low-maintenance solution that you are able to rely on year in and year out.

In addition to this the green IQ range includes extra condensing technology which includes an integrated diverter valve.  It also comes with a wide modulation range of up to 1:10 helping it to adapt to all types of systems. This results in far lower fuel bills especially since it optimises running cycles for lower gas consumption, using Vaillant’s smart heating control to give you, even more, control and reliability.

You will be hard-pressed to find a more capable system for a family home, especially in the combi boiler variety so the green IQ range is really a great system from Vaillant.

Hot Deals Icon

ecTEC Exclusive 843 Spec & Cost:

  • Band Rating: A Rated
  • ERP Rating: A Heat A Water
  • Efficiency Rating: 94%
  • Standard Warranty: 5 Years
  • Output: 36 kW
  • Flow Rate: 17.8 l/min
  • LPG Compatible: Yes
  • Mounting: Wall Mounted
  • Typical Price: (inc VAT) £1,500
  • Typical installation Cost: (inc VAT)* £500 – £1,000
  • Total Cost: £2,000 – £2,500

Is the ecoTEC exclusive green IQ 843 Right for my Home?

Vaillant EcoTEC Exclusive Green IQ 843 Combi Gas Boiler Review

The ecoTec exclusive 843 is designed to heat larger family homes with 15-20 radiators efficiently. If you have a larger detached family home with at least 4 bedrooms and 2 bathrooms then this is the boiler for you. Generally, combi boilers don’t have the output or capacity to heat your home and hot water when it comes to 4+ bedrooms however the green IQ 843 is different.

The Vaillant ecoTec 843 has a highly powerful central heating output of 43kW and an almost unbelievable water flow rate of 17.8 l/min. 

So if you have a large, busy household with multiple showers and taps being used simultaneously then you need a boiler such as this with high output and water flow rate.

You may also want to consider systems that have an integrated cylinder inside the combi system if you have an even bigger home with more bathrooms.

Read more about the Vaillant ecoFIT 825 pure combi for something smaller and more compact.

Hot Deals Icon

What About The ecoTEC exclusive green IQ 843 Efficiency?

The Green IQ range has been designed by Vaillant with green credentials and absolute efficiency. This fantastic boiler has an efficiency rating of 94% and is also ErP A-rated for heating and hot water. This means that even though this is a large output boiler it will still save you money on your heating and lower costs overall.

What if I have a System or Regular Boiler?

Chances are if you have a larger home you will have a system or regular boiler installed with a separate tank or cylinder. You can switch from a system or regular boiler to dramatically increase space and reduce heating costs in your home. What’s the difference? Well, Combi boilers provide heating and hot water on demand so there’s no need for any external tanks or cylinders. 

Hot Deals Icon

What about the Warranty?

Vaillant EcoTEC Exclusive Green IQ 843 Combi Gas Boiler Review

Vaillant offers a respectable 5 year warranty as standard on all their Green IQ boilers however this can be extended to 7-10 years when installed by a Vaillant Advance installer. We do always prefer having a standard 10 year warranty although this boiler is so high output and high flow rate that it makes up for this as it stands out amongst most other competitors.

Vaillant ecoTEC 843 Exclusive Conclusion:

An extremely efficient and reliable green boiler system with some advanced and high output features that compete with even the best boilers on the market. We would rate this system a respectable 8/10.

In terms of alternative boilers, we would also recommend the Viessmann Vitodens 100-W which is a similar price however it is slightly more efficient and has a better heat exchanger, one of the highest fault parts in any boiler. 

If you are looking for a boiler quote, then why not look at our partner company Boiler Central?

Once you’re there, just answer a few questions about your home and it will provide you with a quote calculator, and the best boiler for your home specifically. 

After you have a quote and choose your boiler, you can pay online with flexible financing, book a convenient installation date, and wait for the installation of your next new boiler.

Boiler Central also offers boiler cover which can cover your boiler, and central heating, and even provides an annual boiler service as well as great boiler service prices with selected plans!

Thank you for reading our Vaillant boiler review, if there are other boiler systems you are interested in, we may have just reviewed those too so take a look through the site and hopefully, we can help you in your search for your next new boiler system. 

Hot Deals Icon
Green Central avatar

Written by

Read some of our superb solar panel installation reviews from Trustpilot

Recently had solar panels fitted by Green Central and I can’t speak highly enough of the team. The whole experience has been trouble free and I would recommend them to anyone thinking about having solar panels installed – 10/10!

Rob Schofield


Our installation is now complete! 8 solar panels fitted and the journey from initial consultation through to the end product has been seamless.
Hats off Green central, Credit where it’s due.
Will definitely spread the word!



Recently had six solar panels fitted on my house by Green Central and I couldn’t have asked for a better service. In particular, I have to highlight the exceptional communications through out, the over all smooth running process and completely stress free experience, all down to Green Central. I now have grid independence which is valuable beyond estimation.


Name *
Email *
Phone No. *
Post Code *
Name *
Email *
Phone No. *
Post Code *