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Witten by Bernard Morgan (Engineer).
First Published: March 22, 2021. Updated: November 21, 2023

Worcester Bosch Greenstar i Gas Boiler Review

The Worcester Bosch Greenstar i Gas Boiler is one of Worcester Bosch’s most popular boilers. In this review, we will cover the main features of the Worcester Bosch Greenstar i Gas Boiler, so you can establish if it’s the right model for your home.

Technical Specification:

Manufacturer Worcester Bosch
Model Greenstar i
Condensing Yes
Efficiency Rating 94%
Energy Efficiency Class A Rated
LPG Compatible Yes
Warranty 5 years*
Central Heating Max. Output 24 kW
Mounting Wall Mounted
Weight 31.7 kg
Dimensions 710mm (Height) x 400 (Width) x 330mm (Depth)

Key Features:

  • Very compact and lightweight
  • Can easily be installed in a cupboard or wall-mounted
  • Granted an ‘A’ energy efficiency rating
  • Heats hot water near-instantly and provides continuous access
  • Simple and intuitive boiler control panel
  • Uses a low energy pump which minimises electric usage and bills
  • Can be integrated with Bosch EasyControl which allows you to control your home’s heating wherever you are via a mobile phone or tablet
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  • The Worcester Bosch Greenstar i is a big seller for a reason – it is economical and can accommodate virtually all small and medium-sized family homes
  • Can be installed even in a cupboard because of its compact design – in the kitchen, bathroom or airing cupboard
  • Has a small size and low weight
  • Assembled in Worcester, UK
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Our thoughts:

The Worcester Bosch Greenstar i is a tried and tested model. In addition to being lightweight and small, it is also one of the most energy-efficient boilers on the market. That makes it a great choice for customers looking for a high-quality boiler that will help you reduce your electricity and gas bills.

A quality boiler from a trusted brand

Worcester Bosch has won the coveted Which? Best Buy award for its boilers for over ten years. But what makes Worcester Bosch so special? The engineering and precision that goes into creating Worcester Bosch boilers is great. They also have an excellent rating on Trustpilot, reflecting their commitment to customer service and quality products.

Leading the way to reduce household energy usage

Worcester Bosch is a market leader when it comes to creating environmentally friendly products that do not scrimp on quality and performance when first installed. With a 94% energy efficiency rating, you can guarantee reduced electricity and gas bills and know you are doing your bit to reduce your home’s carbon footprint.

Aluminium heat exchanger

A downside of the Worcester Bosch Greenstar i though, is its usage of an aluminium heat exchanger. An aluminium heat exchanger will offer great efficiency when the boiler is first installed. However, after a few years aluminium will start to corrode and corrosion equals a drop in efficiency. So whilst this boiler offers up to 94% efficiency from installation, this won’t last forever.

It should be noted that the heat exchanger is covered by the guarantee but once out of warranty the repair costs for this will be costly.


On the subject of the warranty, the Greenstar i comes with a guarantee of up to 10 years. However, this is only when the boiler is installed by a Worcester Accredited Installer. Otherwise, it only has a 2-year guarantee.

Available in five outputs

The Worcester Bosch Greenstar i comes in 25 kW and 30 kW models. The 25 kW model is appropriate for smaller homes with one bathroom.

Both boiler models are rated highly for energy efficiency, and the Worcester Bosch Greenstar i was granted an ‘A’ ErP rating.

Choose how to control your boiler 

Once your boiler is installed you can stick to the standard control panel or upgrade to a smart-operated system. The Worcester Bosch Greenstar i is compatible with smart thermostats, or you can use the standard digital thermostats which are easy to adjust.

This model is an engineer favourite because it is so easy to diagnose problems and parts are readily available across the UK.

Not all components are manufactured in-house

Another negative is the fact that not all of the components are manufactured in-house. Whilst this boiler is assembled in Worcester, it is made up of many components from third party companies. This is a negative as there are equivalent boilers at a similar price point that utilise components that are all made in-house. The benefit from these competitors is that their components are designed to work efficiently with each other.

Wide availability of parts 

As the Worcester Bosch Greenstar i boiler is assembled in the UK, parts are widely available. If you need a replacement item you can find spare parts at Screwfix, Plumbase and other plumbing merchants both in-store and online.

Plastic parts

With that said, a downside to the Greenstar i is that many of the parts utilised within it are made from plastic and are more prone to perishing than boilers containing higher quality brass parts.

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