Worcester Bosch Greenstar 25i/30i Boiler Review Re January 27, 2021

Worcester Bosch Greenstar 25i/30i Boiler Review


This article aims to bring the Greenstar i range to life, discussing its design, controls, style, and size, efficiency and warranty, so you can see exactly what all the fuss is about. 

Named the ‘UK’s market leader in domestic boiler’ manufacturing, Worcester Bosch offers a range of Combi, System, and Regular (Heat Only) Boilers. 

According to their website, their mission statements says,

“At the turn of the tap or the tap of an app, our boilers bring physical comfort, but they are also a wellspring of emotional warmth and enhanced wellbeing. Hidden in a cupboard, living on a kitchen wall or sitting in an airing cupboard, our boilers get on with warming lives so that people can get on with living and enjoying life”.

If you would like more information on Worcester Bosch boilers, to help you find the best boiler for you, we have written guides discussing all Worcester Bosch Combi boilersSystem boilers and Regular boilers.

Although the Greenstar i range is now discontinued, it is still a well-known boiler and can be found in many UK homes. For a detailed review of the Worcester Bosch Greenstar 25i/30i Boiler models, grab your cup of tea and biscuits, and let’s get right to it.

Brand Overview of Worcester Bosch

Formed in 1962, Worcester started off as a small business in the small village of St. Martins Gate. The company was then renamed in 1992 to what we know today as Worcester Bosch, due to an acquisition by Robert Bosch, and are now known as the market leaders of boilers in the UK. 

With a trust rating of 4.6 on Trustpilot and over 21,000 reviews, and ranked number 3 of 7 in the Boiler Manufacturer category, Worcester Bosch boilers are renowned for their reliability and efficiency. 

Worcester Bosch say:

“Yes, boilers are our everyday, and heating and hot water our world, but generating and sharing warmth is our reason for being. It’s the value we create and the joy we bring. It’s our calling”.

Whilst the UK Government continues to increase the amount of green fuels being introduced, such as bio-methane and hydrogen, Worcester Bosch has ensured that their customers can be confident that their new gas boiler will run for its lifespan.

Martyn Bridges, Director of Technical Communication and Product Management at Worcester Bosch has said that all Worcester Bosch Greenstar condensing gas boilers manufactured since 2000 can accept a hydrogen blend of up to 20%.

Bridges also said that “the fact that Worcester’s boiler can already accept a blend of up to 20% is further evidence why injecting green fuels such as bio-methane and hydrogen into the UK gas grid is a positive step towards the wider implementation of these new, carbon-free fuels”.

Worcester Bosch is involved in multiple trials with hydrogen gas, including one at Keele University. For the last 18 months, Worcester Bosch has had 150 boilers that have been running up to a 20% hydrogen blend. They are now trialling this in 670 homes in Gateshead.

Worcester Bosch has continued to increase the use of green gases, launching the Hy4Heat programme that is currently trialling 100% hydrogen boilers that are running in specially-built demonstration houses in Northumberland.

More importantly, Worcester Bosch has made significant progress with prototypes and testing, developing hydrogen ready boilers. These hydrogen boilers look almost identical to your typical everyday gas boiler and they are installed in pretty much the same way.

Similar to gas boilers, hydrogen boilers will be connected to the gas mains and then the hydrogen or natural gases will be fed to the boiler from there. 

There are a few small differences when it comes to the internal components of the new hydrogen boilers, such as a hydrogen-ready flame detector and burner.

It is not possible to buy a 100% hydrogen-ready boiler just yet and until there is a reliable supply of hydrogen gas, it wouldn’t make much sense to have one yet anyway.

Now you know about the background of Worcester Bosch as a company, let’s see why the Greenstar i range is Worcester’s best seller. 

Worcester Bosch Greenstar 25i/30i Series Boiler Specs

The first of the Greenstar i range was established in 2005, with the introduction of the Greenstar i Junior. In 2015, this was then rebranded into the new and improved Greenstar 25i and 30i. The Greenstar i range has then been discontinued and replaced by the Worcester Bosch 4000 range, but you’ll still find this well and truly loved boiler in many UK households. 

The Worcester Bosch Greenstar i range is a gas-fired combi boiler designed for small to medium-sized homes. The Worcester Bosch ‘Greenstar i’ is a highly efficient boiler range with an efficiency rating of 90%, which means that it converts almost all of the fuel it uses to heat your home, and none of that fuel gets lost into the atmosphere. It is also very compact and can be installed in various locations, making it an excellent option for small to medium homes with one to two bathrooms and up to three bedrooms. 

Worcester Bosch Greenstar 25i/30i is a condensing boiler, meaning it captures and recycles heat that would otherwise be lost through the flue, making it even more efficient.

This range was awarded the Which? Best Buys for all gas boilers in 2019 and 2020. Being a proud Royal Warrant holder, the Greenstar i model was so successful that even the Royal Family has approved it! 


Both the Greenstar 25i and 30i’s was designed with a sleek and modern look, fitting nicely with your home interior. Their compact and lightweight design meant that they could be installed neatly into your standard kitchen cupboard, out of sight, out of mind. 

Worcester Bosch designed the Greenstar i to be easily accessible, which may mean nothing to you now, but this will result in quick and simple installation and quick annual servicing by your heating engineer and any maintenance that may be necessary in the future.

Worcester Bosch takes pride in their work by saying: 

“Our reputation amongst the installation trade is second to none and we are backed up by market-leading customer service and fantastic guarantees”. 


A known downfall with the Greenstar 24i Junior was the lack of functionality. However, Worcester Bosch took this onboard whilst creating the Greenstar i Combi Gas boiler. 

This boiler is fitted with a wide choice of controls enabling greater comfort in your home. Both the Greenstar 25i and 30i are compatible with the Bosch EasyControl. 

When it comes to the display, the Greenstar i range is simple. There are only four buttons that are used to increase and decrease your central heating and hot water temperature. What more could you ask for!

The rest is digital. Don’t panic, you don’t have to be a computer genius. The LCD digital display will show you the boiler status and temperature clearly, so you have full control over your heating system and boiler. 

For added comfort and control, you can also have the smart thermostat and control your central heating and hot water from the comfort of your sofa, by using your smartphone. 

Designed with you in mind, the Greenstar i range has a built-in low energy pump to reduce electrical usage and also help reduce your carbon footprint. 

For extra peace of mind during those winter months, the Greenstar i boiler range has a condensate discharge pipe installed which is resilient to freezing up to -15 degrees. 

Worcester Bosh Greenstar 25i Combi Gas Boiler

MakeWorcester Bosch
ModelGreenstar 25i Combi Gas Boiler
Condensing BoilerYes
Efficiency Rating93%
Band Rating A-Rated
LPG Compatible Yes
Standard Warranty5 years 
Central Heating Output24kW
Mounting Wall-mounted 
Flow Rate9 l/m
ErP RatingA Heat | A Water
Hot Water Max Output 25kW
DimensionsHeight: 710mm | Width: 400mm | Depth: 330mm


Worcester Bosch Greenstar 30i Combi Gas Boiler 

MakeWorcester Bosch
ModelGreenstar 30i Combi Gas Boiler
Condensing BoilerYes
Efficiency Rating94%
Band Rating A-Rated
LPG Compatible Yes
Standard Warranty5 years
Central Heating Output24kW
Mounting Wall-mounted 
Flow Rate10.8l/m
ErP RatingA Heat | A Water
Hot Water Max Output 30kW
DimensionsHeight: 710mm | Width: 400mm | Depth: 330mm 


One of the many reasons why people love the Worcester Bosch i series gas combi boiler model is the price. It is known for its powerful, high performance at an affordable price. 

The cost of installation may vary based on your location and what you choose to be included in the package. 

To find out the Worcester Bosch combi boiler cost for your home get a boiler installation quote in minutes.

You generally get a better price by buying the boiler with installation packaged in. A WarmZilla boiler package includes the boiler, Gas Safe installation, wireless controls (remote control over your heating system), system filter (to stop nasties getting into your boiler), system cleanse (to flush your system before your new boiler goes in), any flues and extension kits you may require, and inhibitor, to coat the inside of your system to reduce rust.


For extra peace of mind, WarmZilla offers a 10-year warranty on both the Worcester Bosch Greenstar 25i and 30i Gas Combi boilers – this is 5 years more than the standard manufacturing warranty offered by Worcester. 

The Greenstar i vs. The Greenstar Si

There a few things you should consider when deciding on a new boiler or a replacement boiler, these include price, size, controls and energy efficiency. 

If your home has between 1 to 3 bedrooms and 1 to 2 bathrooms, both the Greenstar i and Greenstar Si range would be perfect for you. Their compact size means easy installation, your heating engineer will love this!

However, if you are looking for a new boiler that demands a higher output level, you should look at the Greenstar CDi range. Let’s take a look at the comparison table below to see the difference between the Greenstar 30i and the Greenstar 30Si.

Since the Greenstar i range being discontinued in 2021, Worcester Bosch has since launched their latest boiler model, the Worcester Bosch Greenstar 4000. For those looking for a great alternative to the i range, the 4000 could be perfect for you. Even better, if you are unsure about which boiler is best suited to your home, we now have a Boiler Comparison tool. This tool allows you to compare up to three boiler models or brands at one time, comparing factors such as features, dimensions, warranty and energy efficiency. 

Boiler Comparison Table

Boiler Make & ModelWorcester Bosch Greenstar 30iWorcester Bosch Greenstar Si
ErP Rating93%94%
Dimensions (mm)Height: 710mm | Width: 400mm | Depth: 330mmHeight: 690mm | Width: 390mm | Depth: 280mm
Central Heating Max. Output24kW24kW
Hot Water Max. Output30kW30kW
Flow Rate10.8l/min10.8l/min
Standard Warranty 5 years5 years 

The only difference is size. If you have limited space in your home, although both the Greenstar i and Greenstar Si will fit perfectly in your kitchen cupboard, the Greenstar Si is slightly smaller. 

Apart from that, as you can see, there is no real difference between the both. As mentioned, with an output level of 30kW, both are ideal for small to medium-sized homes. 

Similar boilers to the Worcester Greenstar i from other brands

If you are looking for an alternative gas combi boiler now that the Greenstar i range has been discontinued, we recommend the Ideal Logic+ or Ideal Vogue. 

The Ideal Logic+ can be slightly cheaper than the Worcester Greenstar i range, however, this can depend on the package you choose. The Ideal Logic+ comes with a standard 7 years warranty. Fear not, we have you covered! WarmZilla offers a 10-year warranty on both the Worcester Bosch Greenstar 25i and 30i Combi Gas boilers. 

The Ideal Vogue is a similar price to the Worcester Greenstar i Combi boilers and also comes with a 10-year warranty. 

The Ideal Vogue is great, however, if it’s not for you, then you could take a look at our Boiler Comparison Tool, to compare your current heating system against two other boiler models or brands, to help you find the perfect alternative to the Greenstar i.

We have a guide to all you need to know about Ideal CombiSystem and Regular gas boilers if these are also of interest to you. 

Boiler Brand Comparison Table 

Boiler MakeWorcester BoschWorcester Bosch IdealIdeal
Boiler ModelGreenstar 25iGreenstar 30i Ideal Logic+ C24Ideal Vogue C26
Efficiency Rating93%94%94%93%
Standard Warranty5 years5 years7 years 10 years
Band Rating A-RatedA-RatedA-RatedA-Rated
ErP Rating 

A Heat |
A Water

A Heat |
A Water
A Heat |
A Water
A Heat |
A Water
Central Heating Max. Output 24kW24kW24kW18kW
Hot Water Max. Output25kW30kW24kW26kW
Flow Rate 9 l/min10.8 l/min9.9 l/min10.6 l/min
LPG Compatible YesYesYesYes
Mounting Wall MountedWall MountedWall Mounted

Wall Mounted 

I’m sure you’ve figured out what the fuss is all about by now. 

The Worcester Greenstar 25i and 30i is a high-performance but affordable combi gas boiler, one of the most popular boilers in the industry. 

We now know why even the Royal Family thinks that the Greenstar i range is a great choice of combi boiler from Worcester Bosch.

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