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Vaillant ecoTec Plus 825 Combi Boiler – Review

Vaillant, founded in Germany in 1874, is Europe’s second largest boiler manufacturer. Vaillant’s work developing highly efficient energy products has led to an increasing demand for their boilers – directly competing with the UK’s homegrown energy product manufacturer, Worcester Bosch.

In today’s review, we’ll be taking a closer look at the Vaillant ecoTec Plus 825 combi boiler.

Will the Vaillant ecoTec Plus 825 be suitable for my home?

The Vaillant ecoTec Plus 825 is recommended for homes with up to 3 bedrooms and 1 bathroom. The 825 offers a central heating output of 19.3kW, which will be sufficient to cater for smaller properties. If you’re considering a combination boiler as a replacement to a system or regular boiler, please be aware that if you have more than one bathroom, a combi boiler may not be able to supply enough hot water to cater for your home’s hot water demand. You may be better off with a system or regular boiler to prevent dwindling water pressure.


Like other combination boilers, the ecoTec Plus 825 has a standard control panel installed under the flap at the front of the boiler. The controls allow you to switch off the boiler or lower its output. Due to the simplicity of the 825’s control panel, it’s now easier for an engineer to be able to find any issues with the boiler and diagnose any issues over the phone. Modern boilers are easier to diagnose and call-out fees have been significantly reduced. The build of the boiler itself is also relatively simple, which makes replacing parts and finding spare parts considerably easier.

Seeing as the controls installed on the boiler won’t be enough to have full control of your heating and hot water, Vaillant offers a wide range of controls from mechanical to smart options. Smart thermostats allow you to have all of the control of managing your heating and hot water from your smartphone or tablet.

Smart thermostats come bundled with a smartphone app, which will allow you to schedule your heating, monitor energy use, and remotely switch your heating on and off while you’re away from home as long as you have an internet connection. If you’re not overly keen on the idea of a smart thermostat, you can opt for a wireless programmable thermostat which still gives you scheduling features.


The Vaillant ecoTec Plus 825 measures at 720x440x338mm, which means it may not be suitable for a standard kitchen cupboard. If you’re searching for a more compact combination boiler, the Worcester Greenstar 25Si Compact is your best bet.


Each Vaillant boiler model from the ecoTec range comes with a standard 5-year warranty free of charge for your peace of mind. You can also benefit from an extended warranty of up to 10 years if you decide to install with Hometree.

Energy Efficiency

The ecoTec Plus 825 is an efficient and high-performance boiler, with an ErP (Energy-related Products) rating of 89.3%, which is an A-grade for efficiency. So, in addition to incredible performance, you will start saving money on your energy bills while playing your part in the reduction of carbon emissions.

The ErP directive tests energy products to ensure that they pass specific criteria for performance and efficiency. If a boiler is tested and fails the tests, the directive will step in to recommend design improvements to reduce the amount of energy wasted, thus reducing carbon footprint.


The Vaillant ecoTec Plus 825 is perfect for smaller homes, especially if you have one bathroom with a shower installed and up to 3 bedrooms. The entire ecoTec Plus range offers boilers with a high-quality finish and savings on your energy bills through reduced energy wastage. In addition to high efficiency, the ecoTec Plus boiler range has been awarded the QuietMark for reduced-noise design.

 Vaillant ecoTec Plus 825
ErP rating (energy efficiency)A (89.3%)
Size (HxWxD in mm)720x440x330
Heating output (kW)19.3
How water output (kW)25
Flow rate (litres/min)10.5
Standard warranty (years)5 (extended warranties available)
Other available sizes (kW)32, 35, 38

Which? boiler review

The consumer group Which? review each boiler on the market to find the most (and least) reliable boilers according to a survey completed by thousands of boiler owners. In each review, Which? supply a brand score percentage and star ratings for each category. Take a look at the Vaillant ecoTec Plus 825 ratings below:

Which? Score 
Efficiency rating★★★★★
Brand reliability★★★★☆
Brand customer score★★★★★
Ease of repair★★★★★
Ease of service★★★★★
Availability of parts and spares★★★★★
Build quality★★★★★
Engineer recommendation★★★★★
Brand score80%

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