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Worcester Bosch Greenstar i Gas System Boiler – Review

Worcester Bosch Greenstar i - A review | Boilerhut
Witten by Bernard Morgan (Engineer) & Adam Apperley (Marketing). Published: March 25, 2021. Updated: February 1, 2024

Boiler only price: from £986.28

(Boiler only price: comparing five or more suppliers, including Screwfix and Plumbase. Correct December 2023).

The Worcester Bosch Greenstar i gas system boiler is a popular boiler suitable for small and medium-sized homes. In this review, the team at Boilerhut, comprising engineers with over 40 years of experience, have taken a look at this boiler and have detailed their thoughts.

This boiler is not available as a combi or regular boiler.

Technical Specification:

Manufacturer Worcester Bosch
Model Greenstar i
Condensing Yes
Efficiency Rating 94%
Energy Efficiency Class A Rated
LPG Compatible Yes
Warranty 10 years
Central Heating Max. Output 24 kW
Mounting Wall Mounted
Weight 32.9 kg
Dimensions 690mm (Height) x 390 (Width) x 280mm (Depth)

Key Features:

  • Holds an ‘A’ energy efficiency rating, with efficiency up to 94%
  • Extremely compact and lightweight design, making it easy to install
  • Can be installed in a cupboard because of its small size, or wall-mounted
  • Simple to use manual control panel.
  • Includes frost protection to reduce risk if installed in a non-insulated part of your home
  • Provides a heating output of 24 kW and hot water output of 30 kW
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  • The Worcester Bosch Greenstar Si Compact Gas is extremely compact given its output, making it a popular choice for small homes and apartments
  • Easy to install in a standard cupboard in a kitchen, bathroom or airing cupboard
  • Compatible with smart thermostats
  • Part of the Greenstar ranger which has won Which? ‘Best Buy’ award for several consecutive years
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Our thoughts:

The Worcester Bosch Greenstar i system boiler is a reliable and energy-efficient boiler. As a system boiler this unit requires a full hot water cylinder.

Which? Best Buy award

Worcester Bosch has won the highly regarded Which? Best Buy award for its boilers for several years. Over the years, they have developed a reputation as a reliable and quality manufacturer for boilers both in the UK. However, this quality has been surpassed by other boiler manufacturers in recent years

Energy efficiency

Worcester Greenstar i includes eight models: 9kW, 12kW, 15kW, 18kW, 21kW, 24kW, 27kW and 30kW. The 30 kW model is appropriate for medium-sized homes with one or two bathrooms.

Both boiler models are rated highly for energy efficiency. This is even more pronounced when used with the latest smart thermostat technology. This high-performance boiler has been designed with low energy usage in mind. However, this efficiency won’t last forever, as we go on to below.

Aluminium heat exchanger

A downside of the Worcester Bosch Greenstar i though and the Worcester Bosch range, in general, 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.

Assembled in the UK

The Worcester Bosch Greenstar i is assembled in the UK at Worcester Bosch’s factory and head office in Worcestershire. However, it is only assembled here with many of the individual components in the boiler being manufactured elsewhere by third parties.

Plastic components 

On the subject of parts and components, it should be noted that many of them used in the Worcester Bosch Greenstar i are made of plastic as opposed to the higher quality brass components utilised in equivalent boilers from rival manufacturers.

Wide availability of parts 

That said, the parts and components are widely available across the UK. You can find these at Screwfix, Plumbase and other plumbing merchants both in-store and online.

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