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Vaillant ecoTec Pro 24 vs Worcester Bosch Greenstar 25i Combi Boiler – Review

Welcome to the battle of the boilers. This time it’s between Vaillant and Worcester Bosch’s best-selling boilers, the Vaillant ecoTec Pro 24 and the Worcester Bosch Greenstar 25i.

When trying to decide between a Vaillant and a Worcester boiler, there are a few things to consider, e.g. price, size, control and energy efficiency. These boilers are typically suited to smaller flats and houses with less demand for hot water and heating. However, before we compare the boilers in question, let’s look at the manufacturers first.

Vaillant and Worcester Bosch are both domestic heating and hot water product manufacturers. Both are highly regarded brands with consistently high customer satisfaction scores. Vaillant was founded in 1874 and is currently Europe’s second largest company in this sector, focusing on energy-saving and environmentally-friendly products with polished German engineering.

Worcester was founded in 1962 in the United Kingdom, and later acquired by Robert Bosch GmbH in 1992 to form part of the Worcester Bosch Group. Similarly to Vaillant, Worcester Bosch makes energy-saving goods its main focus, while also creating schemes that promote activities dedicated to conserving the environment for future generations.

Back to the boilers now. The table below shows the basic stats for each boiler model:

 Vaillant ecoTec Pro 24Worcester Bosch Greenstar 25i
Other outputs available28, 3030
ErP rating (energy efficiency)A (89.3%)A (93%)
Size (HxWxD in mm)720x440x330740x418x300
Flow rate (litres/min)9.610.2
Standard warranty55
Noise level output (dB)5048


Both manufacturers offer mechanical and digital controls for their boilers, as well as the option of purchasing their own smart thermostats. Mechanical controls give you control over a 24-hour period, whereas digital controls can give you up to 7 days of programming. Vaillant’s vSMART and Worcester’s Wave smart thermostats provide a smarter option to control your boiler, with the ability to control your heating remotely via your smart phone as well as analysing your heating and hot water consumption. The question is, how do they compare?

The design of the Wave thermostat is incredibly simple and slick with an attractive touchscreen interface. It offers a large variety of options for the user to have full control of their Worcester boiler with smart internet-connected programming. The vSMART by Vaillant, in turn, offers a simple and crystal clear electronic paper display with internet-connected programming to control heating and water.

What are the differences between the two thermostats? The answer is not that many, apart from a couple of things. The Wave can’t manage multiple thermostats across different properties from the same app whereas the vSMART can. Another advantage of the vSMART is its interactive learning and intelligent automatic programming feature, alleviating the need for manual input. A larger issue related to both thermostats is the lack of universal compatibility with boilers from other manufactures. If you purchase either smart thermostat, you must use it with the same manufacturer’s boiler.

It’s a draw between the Vaillant and Worcester Bosch boilers in this round – a point to each.


When comparing the two boilers, the ecoTec Pro 24 is slightly larger in size than the Greenstar 25i. One larger issue worth considering is whether you may be better off with a more compact boiler if you plan to hide your new boiler in a kitchen cupboard. Unfortunately, neither of these boilers are going to be compact enough.

It’s a point for each as neither of the two models fits into a standard kitchen cupboard. 2-2.

Energy Efficiency

ErP (Energy related Product) ratings are designed to improve the energy efficiency of hot water products through testing and raising consumer awareness of their carbon footprint. The ErP directive was introduced by the EU in 2015 to reduce carbon emissions created by energy products. Each product is tested vigorously and should pass certain criteria to be made available on the market.

In terms of boilers, they will be rated based on heating and hot water production efficiency. Both appliances have been given an A rating, which makes them both highly efficient with the highest attainable rating. In this category in particular, the Worcester Bosch boiler has the edge over the Vaillant boiler at 93% energy efficiency.

The Worcester Bosch boiler takes a point over the Vaillant! It’s now 2-3.


Worcester Bosch offer a 5-year standard warranty but also offer an extended warranty of up to 10 years if the Greenstar 25i is registered by a Worcester Accredited installer. Vaillant offer the same warranty period for their ecoTec Pro boiler. They offer a 5-year standard warranty, which can also be extended to up to 10 years if registered by a Vaillant Advanced installer.

It’s a point for each boiler in this category again – 3-4.


Worcester Bosch have won the Which? Best Buy Awards in the gas boiler category for seven years running. Their boilers have also had a 6-year run at an overall rating of 92% for customer satisfaction and engineer recommendations. The Vaillant ecoTec Pro range, in turn, was also awarded the Which? Best Buy Award in 2016 but can also claim to be the only boiler brand to have also been awarded Quiet Mark status by the Noise Abatement Society.

Given the multitude of awards for both, it’s a point to each boiler. The Worcester 25i wins this battle by one point, the final socre being 4-5.

The verdict

That was a close race! In fact, given the quality of the products made by these two manufacturers, we’re basically comparing a Mercedes to a BMW, and we didn’t expect an outright winner anyway. Any decision will therefore most likely come down to brand loyalty or aesthetics.

Brand loyalty and aesthetics aside, the Greenstar 25i is a tad more energy efficient. However, if price is a more pressing concern for you, and you’re not too bothered by the slightly larger size, then go for the Vaillant ecoTec Pro 24. Both will give you the peace of mind you’re looking for.

 Vaillant ecoTec Pro 24Worcester Bosch Greenstar 25i
Energy Efficiency01

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