Vaillant ecoTEC exclusive Green iQ 835 combi boiler review

The Vaillant ecoTEC exclusive with Green iQ 835 combi boiler is designed to be 85% recyclable at the end of its life. (Image credit: Vaillant)

Vaillant ecoTEC exclusive Green iQ 835 combi boilers are built for energy efficiency and sustainability. It has a number of characteristics and features that will help you save money on your energy bills, including its modulation range of up to 1:10 and its high-efficiency stainless steel heat exchanger. The heat exchanger also features unique extra condense built-in heat recovery.

Green iQ mode ensures your running cycles are perfectly optimised, keeping your gas consumption as low as possible. At the end of your boiler’s lifecycle, 85% of its materials can be recycled. The Vaillant ecoTEC exclusive Green iQ 835 combi operates at 94% efficiency and has an ErP rating of A.

However, the Vaillant ecoTEC exclusive Green iQ 835 combi has more than just green credentials to keep homeowners satisfied. It’s fully compatible with vSMART heating controls (which can be purchased separately) and comes with a standard five-year warranty (10 years if installed by a registered Vaillant Advance Partner).

Technical information

The Vaillant ecoTEC exclusive Green iQ 835 is a compact and efficient combi boiler, measuring just 720mm (h) x 440mm (w) x 406mm (d). It has a powerful stainless steel heat exchanger to deliver hot water on demand and an impressive 1:10 modulation range, which enables the boiler to run at a tenth of its maximum output during periods of low demand. This means the boiler can stay on for longer without overheating and makes it more energy efficient. It also helps reduce wear on the internal components. The Green iQ mode helps optimise the running cycle, lowering gas consumption further. Boosting the boiler’s eco credentials, 85% of its parts are recyclable at the end of its life.

• Guarantee options: Five-year standard, extended to 10 years if installed by an approved installer.
• Price range: From £2,225 to £2,725
• Efficiency rating: A
• Output rating: 35kW

Key features

• Highlights: Quiet Mark-accredited, long-lasting stainless steel heat exchanger and impressive 94% efficiency rating.
• Key benefit: The Green iQ 835 is energy efficient and recyclable, making it a great choice for homeowners who value sustainability.
• Fuel: Gas.
• Flow rate: 14.5 litres per minute.

Pros and cons

While the Vaillant ecoTEC exclusive Green iQ 835 combi boiler is one of the top-rated boilers on the market (and one of the best performers we’ve reviewed), it’s always a good idea to consider the pros and cons before making a final decision.

The benefits of installing an ecoTEC exclusive Green iQ 835 combi boiler include:

• Green credentials: The ecoTEC exclusive Green iQ 835 is not only energy efficient during its lifetime, with an efficiency of 94%, but it’s also 85% recyclable at the end of its life.
• Compact: This boiler is fairly compact, measuring just 720mm (h) x 440mm (w) x 406mm (d). It can be wall-mounted or installed in a cupboard.
• Near-instant hot water: The powerful stainless steel heat exchanger ensures continuous, near-instant access to hot water.
• Quiet: The Vaillant ecoTEC exclusive Green iQ 835 produces minimal noise and vibration. It holds the Quiet Mark accreditation.
• Smart management technology: This Vaillant combi boiler is compatible with smart energy management technology, including Vaillant vSMART heating controls that can be managed via a handy app.

Be sure to consider the cons too, including:

• Cost: You can expect to pay from £2,225 to £2,725 for your boiler. This is expensive compared to other combi boilers available in the UK. However, this model’s high efficiency means you could save money in the long term. If you have a small home with fewer than two bathrooms, this boiler may be too powerful for your needs. In this case, you could find a cheaper alternative.
• You need good mains pressure: If your mains water supply has low pressure, you may not experience the benefits of the Green iQ’s 14.5 l/minute flow rate. Ask your installer if this boiler is suitable for you. Installing pumps may help.

Vaillant’s Green iQ combi boiler range offers the company’s best energy efficiency, while 85% of its parts are recyclable. (Image credit: Vaillant)

How does the Vaillant ecoTEC exclusive Green iQ 835 combi boiler work?

The Vaillant ecoTEC exclusive Green iQ 835 combi is equipped with Green iQ technology to make it one of the most efficient boilers on the market. The boiler has a 1:10 modulation range, smart heating controls and a self-adaptive system that has been tested with up to 20% hydrogen blended with natural gas.

Vaillant’s Green iQ technology allows the combi boiler to modulate its output to 10% of its total output, reducing fuel consumption and helping to reduce wear and tear on the internal components. The boiler can be controlled by a smart phone or tablet via the Vaillant vSMART app, allowing users to set the temperature of their home remotely. The smart thermostat “learns” your home’s heating needs, enabling the boiler to adapt its output to run as efficiently as possible. 

As a combi boiler, the Vaillant ecoTEC exclusive Green iQ 835 heats water as it is drawn from the mains water supply and provides central heating. Unlike a system boiler, it doesn’t need a cold water feed, expansion tank or hot water cylinder and only heats water when needed.

How does the Vaillant ecoTEC exclusive Green iQ 835 compare to other combi boilers?

The Vaillant ecoTEC exclusive Green iQ 835 is suitable for many homes, but if you have a slightly higher demand for hot water, you may want to opt for the 843 model. This offers an output of 43kW. Vaillant also sells a 627 system boiler that has a hot water cylinder to meet increased demand.

Another alternative we recommend is the Worcester Bosch Greenstar 8000 Style combi boiler. Both the ecoTEC and the Greenstar cost around £1,400 for the boiler alone, but the Greenstar comes with a maximum 12-year guarantee. It’s suitable for larger homes with more than two bathrooms, packing a punch with its 50kW power output.

We can also suggest taking a look at the Viessmann Vitodens 111-W, which has a 34kW domestic hot water output. Prices start at £1,575 and it comes with a standard five-year guarantee, which can be extended to a maximum of 12 years. You might choose this boiler for its comparatively high flow rate of 18 l/minute.

How much does a Vaillant ecoTEC exclusive Green iQ 835 combi boiler cost?

The cost of the Vaillant ecoTEC exclusive Green iQ 835 combi may vary between suppliers, as can the cost of the installation. However, we do have some estimates to provide a rough indication of what you can expect to pay:

Maintaining the Vaillant ecoTEC exclusive Green iQ 835 combi boiler

The best way to keep your boiler in optimal condition is to have it serviced at least once a year and to balance and bleed your radiators annually. If you find your boiler is losing pressure, check the front control screen. There should be an error code that should indicate the cause of the problem. If the pressure is marked above normal operating levels, you can reduce it by bleeding your connected radiators.

If you spot damp patches around your radiators or discoloured paint around the pipework, you may have a leak that is causing your boiler to lose pressure. This issue will need to be repaired professionally.

What the professionals say

“The ecoTEC 835 combi offers fantastic central heating, hot water output and a decent flow rate, making it an excellent choice for a larger family home. It far exceeds many boilers in terms of how many radiators it can handle but doesn’t compromise on its need to be both cost-efficient and environmentally sound. Get smart and swap your old boiler for the Vaillant ecoTEC exclusive Green iQ 835 to start reaping the benefits.”

• Hometree

“The ecoTEC exclusive with Green iQ boiler features a premium quality stainless steel heat exchanger for superior heat generation. The specially engineered condensing heat exchanger offers built-in heat recovery which helps with efficient operation and will heat your home for less. Overall, the boiler is low on maintenance and easy to install thanks to its Green iQ technology that manages performances so the boiler and its component parts stay in top working order for longer.” 

• Boilerhut

“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.”

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The Vaillant EcoTEC exclusive combi boiler range is compact and Quiet Mark approved, so it’s ideal for kitchen installations. (Image credit: Vaillant)

Customer reviews

“. . . I compared the major combi-boiler systems and Vaillant certainly has the edge for price, availability, and features. Fitment was straightforward, and the electronic operation of the system was easy. The boiler is quiet, efficient and unobtrusive if somewhat bigger than a conventional boiler. With 10 years guarantee and lower running costs by having heating and hot water without the need for a cold water tank, a central heating header tank, and a hot water storage tank, a Vaillant combi boiler has got to be the sensible way to go.”

• Glyn, Trustpilot

“Our heating engineer installed the boiler this June and it appears to be working fine. It fires up very quietly, useful as cited upstairs near the bedrooms, and the hot water comes through quickly. The running cost has dramatically decreased too! I am very pleased.”

• Gill, Trustpilot

“I have an ecoTEC exclusive 835 with Green IQ. Attached to this is their vSmart controller. The combination of these gives a very eco friendly system that keeps my home warm and comfortable. No heat is wasted with hot water tanks. Very economical.”

Graham, Trustpilot

Final recommendation

The Vaillant ecoTEC exclusive Green iQ 835 combi boiler is well suited to large homes with up to four occupants and two bathrooms.

It has a good flow rate (14.5 l/minute), a solid 35kW output and compact size. Vaillant’s high-quality engineering is backed by a fair warranty (up to 10 years via an approved installer). 

But what we really like is its focus on the environment through energy efficiency and optimisation. If you care about keeping your fuel bills (and your carbon footprint) low, Vaillant’s ecoTEC exclusive Green iQ 835 combi’s Green iQ technology will meet your needs in every way.

Methodology

To put together this objective Vaillant ecoTEC exclusive Green iQ 835 Combi boiler review, we first read hundreds of customer and professional reviews, technical documentation, brochures and media articles. We then assessed this boiler against the following criteria for a total score of 100 points:

• The warranty period offered by the brand, for a total of 10 points;
• The overall reputation of the brand based on professional online reviews, for a total of 15 points;
• Trustpilot reviews, for a total of five points;
• Awards and accolades (eg, Which? Best Buy Awards), for a total of five points;
• Customer service performance, for a total of 10 points;
• The price range, for a total of 15 points;
• Efficiency ratings, for a total of 15 points;
• Installation and maintenance network and reviews, for a total of 15 points; and
• Overall performance (temperature, maximum flow), for a total of 10 points.