Worcester Bosch Greenstar 4000 Sizes, Efficiency, Prices, and Alternatives (2024 Review)

Worcester Bosch Greenstar 4000 is the mid-tier boiler model in the Greenstar lineup and comes in both combi and system forms, offering a wide range of benefits for most homes. Worcester Bosch Greenstar 4000 is a compact and quiet boiler, running at just 45 dB. It’s one of Worcester’s most affordable models, but it still boasts high-end energy efficiency features, like a modulating heat exchanger and quick tap technology. These features earn the Greenstar 4000 an “A” energy efficiency rating and popularity among British households.

The Greenstar 4000 comes in 2 sizes in combi form (25 kW and 30 kW), and 3 sizes in system type (18 kW, 21 kW, and 24 kW). Bosch Greenstar 4000 boilers have enough power to supply a small to medium home, with 10 to 15 radiators, and one bathroom. Larger homes may find that the hot water supply is not sufficient and that the radiators are constantly battling to keep the home warm.

Installation costs for the Greenstar 4000 run between £2,600 to £3200, including labour, accessories, and the unit itself. The Greenstar 4000 comes with a 7-year guarantee as standard, but this term increases to 10 years when a Worcester-accredited engineer installs your boiler along with a Greenstar filter, which adds roughly £150 to the costs.

The primary alternative to the Worcester Bosch Greenstar 4000 is the Vitodens 050-W. The Vitodens model is cheaper, but the Greenstar 4000 has the edge both in terms of build quality and performance.

Our Greenstar 4000 review below sheds light on the model’s key features, benefits, sizes, prices, warranties, and alternatives to help you decide if this boiler is suitable for your home.

Worcester Bosch Greenstar 4000 benefits

The main benefits of the Worcester Bosch Greenstar 4000 are its quiet operation, small footprint, great energy efficiency, low cost, and ease of use. More details on the five key benefits of the Worcester Bosch Greenstar 4000 are listed below.

• Quiet operation: The Worcester Greenstar 4000 is a quiet model that operates at a low volume and is less likely to disturb you in your home.
• Small footprint: This is a small boiler, making it suitable for smaller homes with limited space.
• Affordable: The  Greenstar 4000 is one of the most affordable models in the Worcester Bosch boiler range, making it accessible to homeowners with a range of budgets.
• Energy-efficient: The Worcester Greenstar 4000 is part of the energy-efficient Greenstar range, which has won the Which? Best Buy award several times. Energy-efficient models like this help you save money on energy bills and reduce your carbon footprint.
• Easy to use and maintain: The Worcester Bosch Greenstar 4000 is easy to use and maintain, thanks to its standard digital interface and it comes with a standard 7-year guarantee (upgradable to 10 years), which keeps you protected in case of any defects.

What sizes does the Worcester Bosch Greenstar 4000 come in?

Worcester Bosch Greenstar 4000 comes in sizes that range between 12kW and 30kW, and the boiler size selection differs between the combi and system boiler ranges.

Worcester Bosch Greenstar 4000 combi boiler sizes

The Worcester Bosch Greenstar 4000 combi boilers come in 25kW and 30kW sizes. The Worcester Bosch Greenstar 4000 30 and 25kW specifications are listed in the table below.

Specifications	24kW Model	30kW Model
Central heating output	3-24kW	3-24kW
Depth (mm)	310	310
Height (mm)	724	724
Width (mm)	400	400
Energy Rating	A	A
Hot Water Flow Rate	10.5l/min	18.2l/min
Efficiency Rating	94%	94%
Noise Level (dB)	45	45
Warranty (Worcester-accredited installer)	10	10
Suitability	Up to 10 radiators, 1 bathroom	Up to 15 radiators, 2 bathrooms
*Figure depicts domestic hot water heating output

Worcester Bosch Greenstar 4000 system boiler sizes

The Worcester Bosch Greenstar 4000 system boilers come in 12kW, 15kW, 18kW, 21kW, and 24kW models. Below is a table with the Greenstar 4000 system boiler sizes and specifications.

Specifications	12kW* model	15kW* model	18kW* model	21kW* model	24kW* model
Central heating output	1.9-12kW	1.9-15kW	3-18kW	3-21kW	3-24kW
Depth (mm)	310	310	310	310	310
Height (mm)	724	724	724	724	724
Width (mm)	400	400	400	400	400
Heating Efficiency	A/94%	A/94%	A/94%	A/94%	A/94%
Warranty (Worcester-accredited installer)	10 years	10 years	10 years	10 years	10 years
Suitability	10 radiators, 1 bathroom	10 radiators, 2 bathrooms	12 radiators, 2 bathrooms	15 radiators, 2 bathrooms	15 radiators, 2 bathrooms
*System boilers have a single output rating that applies to central heating and hot water

How is the reliability of Worcester Bosch Greenstar 4000?

The reliability of the Worcester Bosch Greenstar 4000 is impressive: the model is considered to be one of the most reliable on the market in its price range. The 3 features below directly contribute to the Greenstar 4000’s reliability.

• Build quality: The Worcester Bosch Greenstar 4000 is built with high-quality components and materials, which makes it durable and long-lasting. Quality components mean that it is less likely to develop faults or require repairs in the long term.
• Efficient heating: The Greenstar 4000 is 94% efficient, which means that 94p out of every pound you spend on gas gets converted to heat. Efficiency reduces strain on the system and means that it is less likely to suffer from wear and tear.
• Advanced controls: The boiler is equipped with advanced controls that allow it to automatically adjust its performance based on the needs of the home. This means that it is less likely to be overworked or underworked, which can reduce the risk of breakdowns.

How is the efficiency of Worcester Greenstar 4000?

The efficiency of Worcester Greenstar 4000 is 94% per the SEDBUK energy efficiency rating. A SEDBUK rating denotes the average annual efficiency of a boiler in a standard household usage situation, with assumptions made about the temperature, usage levels, and other influences.

The Greenstar 4000 has three efficiency features apart from its high SEDBUK rating. First, the Greenstar 4000 features the Quick Tap function to prevent wasting water when running the hot tap. Second, the Greenstar 4000 is compatible with smart home technology. Third, the Worcester Greenstar 4000 offers power modulation that reduces the power draw when system demand is low. These features combine to help to make it one of the most energy-efficient models around.

Below is a more in-depth analysis of the three Greenstar 4000 energy-efficiency features.

Quick Tap

The Quick Tap function allows you to get hot water instantly by simply opening and closing the tap. As you close the tap, the boiler starts working and heats the plate heat exchanger to the set temperature for domestic hot water. Within 30 seconds, you’re able to open the tap again and have hot water ready for use. Quick Tap is a great water saver and is perfect for households that have low hot water demand or need hot water immediately.

Smart home compatible

The Greenstar 4000 is smart home compatible, so you’re able to monitor and adjust the settings from a mobile app even when you’re not home. This feature allows you to avoid wasting energy by switching off your system remotely if you forget to do so before leaving the house.

Power modulation

The Greenstar 4000 boiler saves energy by modulating its power output. This means that the boiler adjusts its heating power to match the exact demand for heat, reducing the amount of energy used and potentially leading to lower energy bills. Modulating its output allows the Greenstar 4000 to operate more efficiently than non-modulating boilers, which simply cycle heat on and off rather than adjusting the output. Modulation saves energy and reduces wear and tear on the unit, potentially extending its lifespan.

How Worcester Greenstar 4000 saves you money on energy bills

The Worcester Greenstar 4000 saves you money on energy bills by wasting very little of the fuel it burns. The Greenstar 4000 has a space heating efficiency of 94%, which means that for every pound you spend on gas, only about 6p are wasted while the rest of the combusted gas converts into heat. In contrast, older, G-rated boilers waste roughly 30p for every pound spent on gas. According to the Energy Saving Trust, upgrading an old, G-rated inefficient boiler to a highly efficient A-rated model such as the Greenstar 4000 produces savings of up to £840 per year on your energy bills. Below is the Energy Saving Trust’s estimate for annual energy savings achieved by converting from a G-rated boiler to an A-rated model, such as the Greenstar 4000.

• Flat: £230
• Mid-terrace house: £420
• Detached bungalow: £445
• Semi-detached house: £540
• Detached house: £840

What are the main features of the Greenstar 4000?

The four main features of the Greenstar 4000 are as follows.

• C6 heat exchanger: The Greenstar 4000 comes with a low-maintenance C6 heat exchanger that adjusts its power needs to conserve energy.
• Quiet operation: The Greenstar 4000 is built with sound-deadening materials and low-noise components.
• High flow rate: The Worcester Greenstar 4000 features a high flow rate of up to 12.3l/min, ensuring enough hot water for families with modest demand.
• LPG compatibility: If you live off the grid, or outside of natural gas coverage, Worcester Bosch can supply the Greenstar 4000 in an LPG-ready version.

C6 heat exchanger

The Greenstar 4000 C6 heat exchanger has three main benefits. First, the C6 heat exchanger modulates down to 4.8kW, making it one of the most efficient heat exchangers on the market. Second, the C6 heat exchanger is easy to maintain. The removable cleaning cover allows quick and easy access to the interior of the heat exchanger, making it simple to service and keep it in top working condition. Third, the C6 heat exchanger comes with a separate, 10-year guarantee to give you extra peace of mind.

Quiet operation

The Greenstar 4000 boiler is able to operate quietly for three key reasons. First, the Greenstar 4000 is made with sound-deadening materials that reduce noise transfer outside the boiler. Second, the Greenstar 4000 has a specially designed combustion chamber that damps down the usual roar of the burners. Finally, the Greenstar 4000 is equipped with a low-noise fan that helps to keep noise levels down, making it extremely quiet in operation.

The features above make the Greenstar 4000 one of the quietest boilers on the market.

High flow rate

The Greenstar 4000 combi boiler is known for its excellent flow rate. The flow rate of the Greenstar 4000 combi boiler is up to 12.3 litres per minute, which is more than enough to meet a mid-sized household’s hot water demands.

LPG compatibility

The Greenstar 4000 boiler is now available in a Liquefied Petroleum Gas (LPG)-compatible version. LPG compatibility provides an alternative energy source for those who live in areas that are off the national gas grid.

What are the Worcester Greenstar 4000 installation costs?

The Worcester Greenstar 4000 installation costs range from £2,650 to £3,250, including the boiler and the fitting. A new Greenstar 4000 costs between £900 and £1,200 depending on whether you opt for the 25 kW or 30 kW model, and installation costs around £1,500. It is necessary to budget between £250 and £550 for your filter, flue, and other sundries on top of the installation costs.

However, the Worcester Greenstar 4000 installation costs vary depending on location, the complexity of the installation, and additional products or services required. Costs increase if the installation involves moving the boiler to a new location in your home. Any upgrades to the heating system or controls increase the price, too.

The quickest way to get an accurate Worcester 4000 quote that accounts for all the aforementioned factors is to use Heatable’s online calculator. Heatable are an online boiler installation company with a free quotation tool that analyses your property parameters to recommend a range of suitable boilers with fixed-price quotes. You’re able to get your own fixed-price quote for a Worcester 4000 and other suitable boilers by filling in Heatable’s online form.

How to get the best deal on a new Worcester Bosch Greenstar 4000?

Get quotes from multiple sources to get the best deal on a new Worcester Bosch Greenstar 4000. Heatable is a great place to start looking for Greenstar 4000 prices. Heatable boiler quotes give you some of the lowest installation costs anywhere, giving you a good jumping-off point when shopping around with other sources. Heatable keep their prices low by operating an online model that doesn’t tie them to any one location. They buy equipment directly from the manufacturers with no middleman, keeping the costs under control.

You can get your own Greenstar 4000 boiler quote from Heatable and see how it compares to estimates from local heating trades.

How long is the Greenstar 4000 warranty?

The Greenstar 4000 warranty is 7 years from the date of installation as standard. However, the warranty increases to 8 years if you opt to have your boiler installed together with a Greenstar filter by a Worcester Bosch accredited engineer. Paying the £150 premium on top of the Greenstar filter and Worcester Bosch-approved engineer installation increases your guarantee to a full 10 years. Alternatively, you’re able to get the 10-year warranty as standard if you get your Greenstar 4000 from Heatable.

Is Worcester Bosch Greenstar 4000 right for my home?

Making the decision on whether a Worcester Bosch Greenstar 4000 is right for your home depends on the following 3 factors.

• Required heating output: The Worcester Bosch 4000 is best suited to small to medium-sized homes with 15 or fewer radiators and 1 bathroom. You’ll need to consider a higher-capacity boiler if your home is larger than this.
• Required flow rate: The Greenstar 4000 has a flow rate of up to 12.3l per minute, which may not suffice if you run several taps and showers at the same time.
• Budget: Worcester Bosch products are some of the best on the market, and the brand name carries a premium that reflects the reputation. There are cheaper alternatives, like the Baxi 600, Logic Plus 30, and Vitodens 050-W that may suit your needs just as well.

Heatable’s free online boiler calculator is an excellent resource if you’re not sure which boiler is suitable for your home. The calculator requires you to input your property parameters (no personally identifiable data required), after which it returns a range of suitable boiler models along with fixed-price quotes.

What is the best alternative to the Greenstar 4000?

The Vitodens 050-W is the best alternative to the Worcester Bosch Greenstar 4000 and one of the best combi boilers on the market. The Vitodens 050-W is the best alternative to the Greenstar 4000 for the 7 reasons below.

• Affordability: The Vitodens 050-W is more affordable than the Greenstar 4000, making it a cost-effective option for homeowners.
• Energy efficiency: The Vitodens 050-W has an extremely high energy efficiency rating of 97%, which can help lower energy bills.
• Compact design: The Vitodens 050-W is slightly smaller than the Greenstar, making it ideal for homes with limited space.
• Easy installation: The Vitodens 050-W is easy to install, which reduces installation costs.
• Reliable performance: The Viessmann Vitodens 050-W is known for its reliable performance, which provides peace of mind to homeowners.
• Ease of use: The Vitodens 050-W has user-friendly controls and an intuitive interface, making it easy to operate.
• After-sales support: Viessmann, the manufacturer of the Vitodens 050-W offers excellent after-sales support, including maintenance plans and customer service. In addition, Viessmann offers a warranty of up to 10 years with registration and approved installation.

​​The below table compares the basic specs of the Greenstar 4000 and Viessmann Vitodens 050-W.

Specifications	Worcester Bosch Greenstar 4000	Viessmann Vitodens 050-W
Depth (mm)	310	300
Height (mm)	710	700
Width (mm)	400	400
Energy Rating	A	A
Boiler Outputs	25 & 30kW	25 & 30kW
Boiler Tyle	Combi/System	Combi/system
Hot Water Flow Rate	10.5l/min – 12.3l/min	10l/min – 12.3l/min
Efficiency Rating	94%	97%
Noise Level (dB)	42	46
Warranty (Trained Installer)	10 Years	10 Years

Verdict: Is Worcester Bosch Greenstar 4000 worth it?

Worcester Bosch Greenstar 4000 is worth it if you’re willing to pay a premium for benefits such as reliability, energy efficiency, quiet operation, and an easy-to-use interface. The Greenstar 4000 is ideal for homes with up to 15 radiators and 2 bathrooms, and low-to-moderate hot water demand. The main downside we found with the Greenstar 4000 was its price. Models like the Vitodens 050-W offer similar performance for less money, and this might spoil the appeal to budget-conscious homeowners.

Overall, the Worcester Bosch Greenstar 4000 is a suitable option for homeowners who are looking for a high-quality, reliable, and energy-efficient boiler.

Worcester Bosch Greenstar 4000 FAQs

Below are eight of the most frequently asked questions about the Worcester Bosch Greenstar 4000.

How many radiators can a Worcester 4000 run?

A Worcester Bosch Greenstar 4000 boiler can run up to 15 radiators. The Greenstar 4000 30 kW combi is best suited to homes with no more than 15 radiators and 1 bathroom for optimum performance. The Greenstar 4000 25kW combi boiler is able to handle homes with 1 bathroom and up to 12 radiators.

A Greenstar 4000 system boiler is able to serve up to 15 radiators and 2 bathrooms.

What is the difference between Greenstar 4000 and 8000?

Below are the three differences between the Greenstar 4000 and 8000.

• Power output: The Greenstar 8000 has a higher power output than the Greenstar 4000. The Greenstar 8000 is available in sizes up to 50 kW, while the Greenstar 4000 is available in sizes up to 30 kW. This means that the Greenstar 8000 is better suited for larger homes that require more heating power.
• Hot water flow rate: The Greenstar 8000 has a higher hot water flow rate than the Greenstar 4000. This means that the Greenstar 8000 can deliver hot water more quickly and efficiently, making it a better choice for properties with high hot water demand.
• Price: The Greenstar 8000 is more expensive than the Greenstar 4000. This is due to its higher power output, advanced control options, and improved hot water performance. However, the higher cost may be offset by the potential energy savings and improved performance of the Greenstar 8000 over the long term.

What is the difference between Worcester 2000 and 4000?

The following are the three differences between the Greenstar 4000 and 2000.

• Controls: The Greenstar 4000 has more advanced control options than the Greenstar 2000. The Greenstar 4000 features an advanced control panel with a digital display, allowing for easy programming and control of the boiler. The Greenstar 2000, on the other hand, has a simpler control panel with basic functions.
• Hot water flow rate: The Greenstar 4000 has a higher hot water flow rate than the Greenstar 2000 with up to 12.3 litres per hour, vs. 12 litres per hour on the 2000. This means that the Greenstar 4000 can deliver hot water more quickly and efficiently, making it a better choice for properties with high hot water demand.
• Price: The Greenstar 4000 costs more than the Greenstar 2000, but offers advanced features and improved energy efficiency that help reduce energy bills and improve overall comfort.

How long should a Worcester Bosch Greenstar boiler last?

A Worcester Bosch Greenstar boiler should last between 10 to 15 years. The lifespan of a Worcester boiler depends a lot on how well it is maintained, as well as the strain put on it by use. You’re able to extend the lifespan of a Greenstar 4000 boiler by installing a magnetic system filter in order to catch debris and prevent sludge buildup. Additionally, an annual boiler service is a must for early detection of faults before they deteriorate and become big problems.

Is Greenstar 4000 a good boiler?

Yes, the Greenstar 4000 is a good boiler for three reasons. First, the Greenstar 4000 is very well made, with quality, high-end components used throughout. Second, the Greenstar 4000 makes use of energy efficiency features, like power modulation, to reduce running costs. Third, the Greenstar 4000 is exceptionally quiet thanks to the sound-deadening materials used in its components.

However, it’s important to consider two things when you buy a Greenstar 4000. First, make sure that the Greenstar 4000 comes in the right boiler size for your home. Second, remember that proper installation and ongoing maintenance dictate how well it performs in the long run.

Is Worcester Bosch 4000 hydrogen-ready?

Yes, the Worcester Bosch 4000 is hydrogen-ready. Like all boilers made by Worcester Bosch, the Worcester Bosch 4000 is able to run on hydrogen blends. The ability to run on a hydrogen mix is great news if you’re planning to try and future-proof your home.

How do I refill my Greenstar 4000 boiler?

You refill your Greenstar 4000 boiler by using the automatic filling feature. The Greenstar 4000 has an automatic filling facility that tops up the water in the system as necessary. When the system is installed, the engineer will program the filling device to ensure that the pressure remains constant.

How do you drain a Worcester 4000?

You drain a Worcester 4000 by following the six steps below.

1. Unplug the boiler, and allow a few hours for the water to cool to prevent injuries.
2. Turn off the water intake valve to prevent more water from entering the system.
3. Look for the drainage valve. This will be found on the lowest point of the lowest radiator in the home.
4. Securely fit a hose to the drainage valve – try to make sure the hose is long enough to reach a sink, or outside.
5. Open the radiator valve, and watch the water drain out. When water stops flowing, the system is fully drained.
6. Remember to close the drainage valve before doing anything else.