Catwalk confidence with substance behind the eyes. Read the article, don't read the article - just buy the Worcester 4000 (here's why).
Worcester Bosch has been one of the best selling boiler brands in the UK boiler market for decades, earning a solid reputation among both installers and customers and holding the Which? Best Buy Award for 14 years and counting.
The 4000 is your little black dress. It's your denim jeans. Your oldest boots. It's... you're own face? It's trusty. That's the message here.
The Worcester Bosch Greenstar 4000 series is one of the brand's latest innovations, replacing their best-ever-selling boiler, the Greenstar i.
On May 17th, 2021, Worcester simultaneously launched the new 4000 combi (to replace the Greenstar i) and the new 4000 system boiler range which will replace the equally successful Greenstar i system range.
A double delight for boiler enthusiasts (all 3 of them).
Worcester Bosch Greenstar 4000 Boiler Review
In this 4000 boiler review, we've scored the 4000 in 4 key areas, including:
Reliability: 5/5 Stars
Performance: 4/5 Stars
Warranty: 5/5 Stars
Price: 4/5 Stars
Designed to sit between the 2000 and 8000 series boilers, the 4000 is the brand's mid-range boiler.
The 4000 is offered in multiple sizes including 25kW and 30kW, all coming with an impressive 10-year guarantee for parts and labour (when purchased via Heatable).
Let’s take an in-depth dive into the 4000 and everything that it has to offer…..
Prefer video? Check out our Youtube review of the Worcester Bosch 4000 below:
Main features of the Worcester Bosch 4000 Boiler
Worcester Bosch’s mid-range model
Designed to have a quieter operation than the Greenstar i
Compatible with all Worcester Bosch controls and third-party controllers such as Hive, Nest, tado etc.
Ideal for small and medium sized homes
Easy access with removable side panels
10-year guarantee on parts and labour (when purchased via Heatable)
ErP rating 94%: A-rated
Dimensions: 710 x 400 x 310
Specifications:
Warranty: Up to 10 years | Energy Efficiency Rating: A | Output Rating (kW): Available in 25 and 30 kW options | Water Flow Rate (litres/minute): 10.5 or 12.3 depending on the model | Size (mm): 724 × 400 × 310 | Price: Starts from approximately £1,152.99
Pros:
Quieter than many competitors, ideal for noise-sensitive environments.
Works with popular smart home systems like Hive, Nest, and tado°.
10-year parts and labour guarantee through Heatable.
Excellent customer support and aftercare services.
Small footprint, fits easily in tight spaces.
Cons:
It is more expensive upfront compared to budget models like Alpha or Ideal.
Best suited for small to medium-sized homes, not ideal for large homes.
Lacks some of the advanced diagnostics features found in Viessmann models.
Reliability: 5/5
The Worcester Bosch 4000 combi boiler has replaced the Worcester Bosch Greenstar i, the brand's best-selling boiler model and just like the previous version, it offers incredible value for money and reliability.
Trustpilot Reviews
For illustration, on TrustPilot, Worcester Bosch has racked up an incredible amount of reviews. As of September 2024, almost 50,000 customers left a review. An incredible feat.
The brand has an average rating of 4.7 stars out of 5, a huge achievement for a brand selling so many boilers, a testament to their reliability and amazing aftercare.
Moreover, in our article ranking the best boiler manufacturers, the brand was rated as offering the best combi boilers of the year; so, this is certainly a boiler brand with credibility.
If you are left wondering whether to choose between Viessmann and Worcester, check out our recent comparison between the two brands.
Which? Boiler Survey Results
Worcester has carried the Which? Best Buy Award for over 14 years now and being based in the UK also means parts are very easy to obtain and their customer service is reliable.
In fact, in the most recent annual boiler survey feedback was gathered from over 100 installers and received several high 5-star ratings the consumer choice organisation considers most important to consumers, including full marks for their build quality and availability of parts and spares.
Performance: 5/5
Worcester Bosch 4000 Combi Boiler Power Outputs:
The Greenstar 4000 combi boiler range is available in the following sizes (power outputs):
25kW
30kW
The 25kW combi boiler has a heat output of 25kW and a flow rate of 10.5 l/min, making it suitable for small properties and flats that may have limited hot water demands.
The 30kW has an additional 5kW of power and a flow rate of 12.3 l/min making it suitable for medium sized properties with higher hot water demands.
Want to know which boiler power is right for your home? Check out our boiler sizing guide
You can check the latest deals on Worcester Bosch boilers here, and see how the brand compared to another market leader in our Worcester Bosch vs Vaillant Boilers comparison.
Worcester Bosch Greenstar 4000 System Boiler
The 4000 range is also offered as a system boiler, this is a different type of boiler, ideal for homes with multiple bathrooms and hot water outlets.
The system boiler is a wall hung unit available in either white or black and requires a separate hot water storage cylinder.
The Greenstar 4000 System boiler is available in the following power outputs:
12kW
15kW
18kW
21kW
24kW
Which 4000 model is right for your home?
If you’re curious about the size boiler that’s most suitable for your home, use our free tool. It will do all the hard work for you, calculate the boiler you require and provide a fixed price.
Efficiency of the Worcester Bosch 4000
The Worcester Bosch Greenstar 4000 is accredited as A-rated for energy efficiency, with an incredible 94% efficiency.
Looking for a more budget-friendly boiler? Check out our review of the Worcester Bosch 2000, or if you want the latest and greatest check out the Worcester Bosch 8000.
Want to know how these boilers compare, check out our 2000 vs 4000 vs 8000.
Learn all about combi boilers in our what is a combi boiler guide and see how the brand fared against Baxi in our Worcester Bosch vs Baxi comparison.
The image above shows a Worcester Bosch 4000 installed by the Gas Safe engineers here at Heatable. Get your free quote from us here.
Controls & Features of the Greenstar 4000
SimpleSwitch
Since the 4000 is set to replace the Greenstar i range, Worcester has 'SimpleSwitch', this essentially means it will fit within the Greenstar i footprint of any of the condensing boilers within that range, ideal for previous customers wanting to make an upgrade with limited disruption.
Upgraded Exterior
The design language of the new 4000 series is carried over from the 2000 and 8000 range.
Curved edge casings and the digital display is a nice move away from the boring square boxes of old.
The new user-friendly LCD display upgrade and easy to use push control buttons are also a huge improvement. It also features wireless connectivity, allowing you to connect the boiler to Bosch EasyControl and control the boiler remotely from your smartphone or other electronic device.
This new digital pressure gauge is particularly convenient, as it alerts users to pressure changes and signals when a refill is needed, enhancing both usability and maintenance (as shown in the image below).
Ben Price/Heatable
Want to learn more about Worcester Bosch? Check out our complete guide to the brand.
Easy Access Side Panels
The new design of the 4000 also means the boiler is easier than ever to gain access to, allowing engineers to service and repair your boiler with minimal disruption.
Intelligent Filling System
Just like the Greenstar i range, the Greenstar 4000 range is compatible with Worcester’s intelligent filling system.
This system uses software that is able to maintain your boiler’s pressure at its optimum level. If the pressure drops, the internal filling valve will jump into action and automatically refill the system and turn back off once done.
It will also alert you if the boiler is losing too much pressure, allowing you avoid unnecessary engineer callouts.
...note: this feature is only available with the combi boiler and not the 4000 system boiler.
The Worcester Bosch 4000 is also compatible with many of Worcester’s other controls, including:
MT20
Comfort+
Comfort+ Stats RF
Comfort+ RF
Easy Controls
System Filter Compatibility
Building regulations now stipulate a system filter is fitted with all new installations.
The 4000 series will be compatible with the Worcester Greenstar System filter and third party filters.
However, to access the maximum guarantee lengths, Worcester stipulates you must install their filter to benefit from the increased cover.
Warranty: 5/5
Worcester Bosch Greenstar 4000 Guarantee
An important consideration when buying a new boiler is the warranty or in the case of Worcester Bosch the far superior guarantee.
...What’s the difference between a warranty and a guarantee?
Essentially, a guarantee is an agreement from the brand that they will attend your property and repair or replace the boiler within a reasonable timeframe.
Most other boiler manufacturers only offer a warranty as standard, this is an agreement to investigate the problem, but is not an unconditional agreement to fix or repair it for free.
With the 4000 range, you will be securing an industry leading ten year guarantee on parts and labour (when purchased via Heatable), which offers you the peace of mind for the next decade.
Price Point: 4/5
Worcester Bosch 4000 Combi Boiler Costs
The 4000 is a mid-range boiler offered by a premium boiler brand, so although it’s not their most expensive boiler, it’s not the cheapest boiler you’ll find either. But that’s the price you pay for excellent quality and aftercare.
The exact costs of the boiler (including Gas Safe installation) may vary depending on your type of property, hot water demands and a whole host of other facts.
So, to make it easy, we have designed a quick questionnaire that will give you an instant fixed price. It takes about 60 seconds to complete.
Worcester Bosch Greenstar i vs Greenstar 4000 - What’s the difference?
The Worcester Bosch Greenstar i was Worcester’s mid-range boiler and their best selling combi boiler range, which has now been replaced by the better looking Worcester Bosch Greenstar 4000. So what’s the difference and what’s changed?
The Worcester Bosch Greenstar 4000 series marks a significant advancement in the brand’s innovation, building on the success of the Greenstar I, their best-selling boiler, which it has now replaced. During internal evaluations at Heatable headquarters, several key improvements were identified.
The image above shows the Greenstar 4000 (left) and Greenstar I (right).
The new 4000 range has a quieter operation and provides a higher hot water output.
Greenstar-i | Greenstar 4000 | |
Dimensions | H 710 | H 710 |
Flow Rates | 25kW - 10l/min | 25kW - 10.2l/min |
LCD Display | Yes | Yes |
Frost Protection | Yes | Yes |
As you can see in the above comparison table, there are many similarities between the two models. The 4000 does have smaller dimensions thanks to its new, sleek design, allowing it to more snuggly fit into tight spaces, including kitchen cupboards.
The 4000 also offers a higher flow rate of 10.2 litres a minute, meaning it provides faster hot water to your water outlets. Both boiler models have easy-to-use controls, an easy-to-read LCD digital display screen, and built-in frost protection to guard against freezing during the colder months of the year.
Other notable Greenstar 4000 innovations we think are worth highlighting, include the following:
Quieter Operation: Engineered to operate more quietly than its predecessor, the Greenstar 4000 ensures a less intrusive presence in your home.
Compatibility with Smart Controls: This boiler is compatible with all Worcester Bosch controls and popular third-party controllers like Hive, Nest, and tado°, allowing for seamless integration into smart home systems.
Optimal for Small to Medium-Sized Homes: Its design and capabilities make it ideal for smaller and medium-sized homes, offering efficient heating without the bulk.
Ease of Maintenance: With removable side panels, the Greenstar 4000 is designed for easy access, simplifying maintenance and service tasks.
Extended Warranty: It comes with a 10-year guarantee on parts and labour when purchased through Heatable, providing long-term peace of mind.
High Energy Efficiency: With an ErP rating of 94%, it holds an A rating for energy efficiency, ensuring lower energy bills and reduced environmental impact.
Compact Dimensions: Measuring 710 x 400 x 310 mm, it is compact enough to fit discretely within your home.
Our Verdict on the 4000
The Worcester Bosch Greenstar 4000 is a mid-range model offering all of the most essential features and contemporary exterior at a competitive price.
The 4000 is replacing Worcester’s best selling Greenstar i range and offers all the same features, but has some additional perks including a more compact design for a streamlined installation into your standard kitchen cupboard.
It also offers a higher flow rate of 10.2 litres a minute which means that it provides faster hot water to your taps and showers.
The 4000 also benefits from the brand's most recent innovations such as the intelligent filling system, frost protection, ECO mode and wireless connectivity.
The boiler's exterior is also a huge improvement offering homeowners not only a boiler that works great, but one that looks great. The design language of the new 4000 series is carried over from the 2000 and 8000 range. Curved edge casings and digital displays are a nice move away from the old boiler models.
Check the latest price of the Worcester Bosch 4000 boiler.
Finally, with the brand winning the Which? Best Buy Award for 10 years in a row, receiving extremely high TrustPilot reviews and offering an industry leading 10 year guarantee (not just a warranty), we fail to see any rivals catching up anytime soon.
Should you buy it? If you're looking for a reliable boiler from a brand that’s been winning awards for the past 10 years, certainly.
Looking for the best deal on a Worcester Bosch 4000?
If you’re aiming to get the best deal on a new boiler, consider getting a quote from us, here’s why:
Gas Safe installation within 24 hours.
Thousands of satisfied customers with an average score of 4.9 on Trustpilot, surpassing the market leader.
Which? Trusted Trader: Heatable is proudly recognised as a Which? Trusted Trader.
Price match guarantee: We will match any like-for-like cheaper quote.
Flexible payment options, including interest-free finance.
Up to 12-year guarantee on selected boilers.
Fixed price guarantee: No hidden costs.
Save your quote and decide later.
Get an instant fixed price on a new boiler, here.
To learn more about boilers, visit our advice section, check out our YouTube channel, or read customer testimonials here.
Heat Happy.
