Worcester Greenstar 4000 25kW Combi Boiler

Price: £1,541.00

The Worcester Bosch Greenstar 4000 25kW combi boiler is a high performance and efficient combi boiler for medium-sized homes. It’s a sought-after choice for those looking to upgrade their heating system.

Heat output: 25kW
20% Hydrogen-mix Ready
Aluminium Silicon Heat Exchanger

(Boiler-only price: comparing five or more suppliers, including Screwfix and Plumbase. Correct February 2024).

Key Features

The Worcester Bosch Greenstar 4000 25kW combi boiler is a 94% efficient wall-mounted gas and LPG condensing boiler. This is a premium Worcester Bosch’s combi boiler.

Key Features

Compact dimensions – install in a cupboard or kitchen
Modulation of 1:10 – makes this boiler extremely efficient
94% / A-rated efficiency
Maximum 10-year warranty
Can heat even larger homes with two bathrooms
Push-button LCD
Smart energy system technology included with Bosch EasyControl

Size and Installation

25kW Gas & LPG condensing boiler (LPG version available)
Dimensions – 724mm high, 400mm wide and 310mm deep
Quiet operation means it doesn’t need to be in a cupboard

Control

Front-mounted screen and controls
User-friendly

Environmentally Friendly

Low CO2 emissions for reduced environmental impact
20% hydrogen blend ready
1:8 modulation enables efficient running at 10% of maximum power

More Information

More About The Worcester Greenstar 4000 25kW Combi Boiler

The Worcester Bosch Greenstar 4000 25kW is perfect for medium-sized homes. These have been designed to look good. This makes it easier to install outside of a kitchen cupboard. Worcester Bosch has an excellent reputation in the UK and are the largest manufacturer of boilers. They are assembled in Worcester.

Price

Starting at £1,541 (average price from five plumbers merchants in February 2024), the Greenstar 4000 is a premium-priced boiler. It’s also more expensive than some competitor models of similar of better specification.

Efficiency

Able to hit 94% efficiency and achieve an A rating for heating and hot water, the Greenstar 4000 range is an efficient combi boiler. It will help you save money, especially if you are upgrading from an older non-condensing boiler.

Aluminium heat exchanger

The Greenstar 4000 comes equipped with an aluminium heat exchanger. As discussed in other guides, aluminium is a good material but not as good as stainless steel. Aluminium tends to corrode more quickly and loses efficiency over time.

The 4000 has up to 10 years of warranty coverage. But, there will be strict conditions in which the heat exchanger will be replaced. And if it breaks down outside the 10 years the cost to replace will be high.

The 10-year warranty is only offered when installed by a Worcester Bosch-trained heating engineer and with specific hardware such as Worcester filters.

Equipped with innovative technology and optimised heat and hot water output

The Worcester Bosch is designed and built to run as quietly as possible. This means it can be installed in many places without disruption.

Control your boiler remotely

Worcester Bosch’s EasyControl system allows heating control from your phone. From anywhere in the world. As you have better control you can overrule the standard heating schedule if you’re not home. This means not wasting energy.

Boilerhut Review

Our Thoughts

Written by Bernard Morgan (Engineer). Published: February 14, 2024. Updated: February 24, 2026

The Greenstar 4000 25kW combi boiler is one of their most popular boilers. It is popular because of its range of power, compact size and modern design. It is more reasonably priced than it’s ‘bigger brother’ the 8000 series.

The Worcester Bosch Greenstar 4000 received an excellent rating from Which? and awarded Which? Best Buy status for the past few years. This is a good boiler. If looked after properly it can easily last 10 or more years.

However, as this boiler has an aluminium heat exchanger, we don’t often recommend them to customers. The reason for this, is that even if the boiler is looked after properly, it can still lose 10% efficiency over 10 years. This is money spent on gas bills. Money that is increasing every year due to efficiency loss. You can read more about this here >

Performance 8/10

At 94% efficiency, this boiler will save people money when upgrading from older boilers. However, as already discussed, this won’t last and aluminium exchangers can lose 10% efficiency over 10 years.

Quality 9/10

Worcester Bosch uses a mixture of brass, copper and plastic parts in their boilers. If well looked after they should all be ok, but we would tend to recommend boilers with premium components.

Value 8/10

The Worcester Bosch 4000 25kW combi boiler is above average for value. You will be getting a good boiler. But over time it will cost you more and more. There are other brands available with higher-quality internal components which will last much longer. Viessmann, for example, use stainless steel heat exchangers and copper and brass fittings. Read our Worcester Bosch vs Viessmann guide.

Customer Satisfaction 9/10

Worcester Bosch is the largest manufacturer of boilers in the UK. They have hundreds of thousands if not millions, of boilers in homes all across the country. They are a great boiler brand. The problem, from our point of view, is cheaper internal parts. If well looked after they are great. But they will lose efficiency over time.

Specification

Manufacturer	Worcester Bosch
Model	GREENSTAR 4000 25kW
Condensing	Yes
Efficiency Rating	94%
Energy Efficiency Class	A Rated
Modulation Range	1:8
LPG Version	Yes
Warranty	Up to 10-year comprehensive warranty
Hot Water Output	25kW
Combi Hot Water Flow Rate	10.2 litres/minute
Central Heating Output – 50/30 °C	3.1-25kW
Mounting	Wall Mounted
Colour	White
Weight	35kg
Dimensions – Height	724mm
Dimensions – Width	400mm
Dimensions – Depth	310mm

What’s Included

If you need a new or replacement boiler or are looking at having a central heating system installed, get an online quote (it takes less than 1 minute), and you’ll get an instant price. But why choose Boilerhut:

Prices include everything to ensure the ongoing efficiency and longevity of your new boiler (flushing, filters, labour, and VAT etc).
Manufacturer-trained installers for full warranty on completion
Next day boiler installation. Quick central heating system installation.
‘Excellent’ 5* customer satisfaction on Trustpilot.
Boiler finance options available for central heating or boiler installation.
10 to 12-year warranty on boilers.
Fixed prices. No hidden extras.
Get up to three quotes for different-tier boilers.
Instant, no-obligation quote in less than 1 minute.

Worcester Greenstar 4000 25kW Combi Boiler

Price: £1,541.00

Key Features

Size and Installation

Control

Environmentally Friendly

More About The Worcester Greenstar 4000 25kW Combi Boiler

Our Thoughts

Performance 8/10

Quality 9/10

Value 8/10

Customer Satisfaction 9/10

Support

Further reading and more information

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