Worcester Bosch Greenstar 4000 Range Review

Company type: Manufacturer

HQ: Worcester, England

Founded: 1962

CEO: Carl Arntzen

The Worcester Bosch Greenstar 4000 is a brand new range of compact and stylish boilers, available in both combi and system options. With its sleek design and great energy efficiency, it is bound to become one of the UK’s favourites. We reviewed the range to tell you more about its advantages and characteristics.

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Is the Worcester Bosch Greenstar 4000 suitable for you?


Designed to sit between the 2000 and 8000 series boilers, the 4000 is Worcester Bosch’s mid-range boiler. Therefore, it’s best suited for small and medium sized properties. If you require a more powerful boiler, consider the Greenstar 8000 range instead. To find out more about the different Worcester Bosch boiler options for your home, click below.

Find the perfect boiler for your home

The 4000 range features the following boilers:

  • Worcester Bosch Greenstar 4000 combi boiler

  • Combi boilers are excellent solutions for homes with limited space, as they do not require bulky cylinders to store hot water. The Worcester Bosch Greenstar 4000 combi model comes in two energy outputs: 25 kW and 30kW. To read more about combi boilers, click here.

  • Worcester Bosch Greenstar 4000 system boiler

  • The Worcester Bosch Greenstar 4000 system boiler is perfect for homes that have multiple bathrooms. There are five different power outputs (12-24 kW) available for the Worcester Bosch Greenstar 4000 system boiler: 12kW, 15kW, 18kW, 21kW, 24kW.

Is the Worcester Bosch Greenstar 4000 energy efficient?

Both the combi and system models achieve an impressive 94% level of efficiency. Efficiency levels are calculated by assessing how much of the fuel, so in this case, gas, is turned into heat and how much is wasted during the process. 94% efficiency means that just 6% of the energy used is lost during the heating process and these 6% leave the system as gases emitted via the flue pipe. Put in other words, 6 pence is lost for each pound paid towards your energy bills.

When compared to other boilers, 94% is an excellent energy efficiency performance, well within the ‘A’ energy efficiency category. Only a few boilers beat this efficiency level, for example, the Vitodens 050-W 29kW with an energy efficiency of 97%.

Key Features

These features come with both combi and system boiler options.

Hydrogen-ready boilers

Although the Worcester Bosch Greenstar 4000 range is compatible with natural gas, it can also run on a 20% hydrogen blend. With the government’s plan to popularise the use of gas and hydrogen blends by 2025 to reduce carbon dioxide emissions, you can be confident that your boiler is perfectly suitable for this change. This means that the unit is ready should the gas network make a switch to hydrogen.

Simple Switch: swap your old boiler for The Greenstar 4000 with ease

Worcester Bosch’s Simple Switch allows you to quickly and seamlessly replace your older Greenstar i boiler with a new 4000 model. Simple Switch will make the replacement incredibly easy for your engineer. To make sure the transition goes as smoothly as possible, fixing points and the distance from flue to valves match predecessors for minimum re-work. For your convenience, there is also a wall-frame with a pre-piping option to get all the pipes connected even before the boiler is hung.

Reduced noise levels, compared to Greenstar 30i

The Worcester Bosch Greenstar 4000 range operates at 45 dB, which makes the 4000 range boilers relatively quiet. For reference, a normal conversation between two people is around 65 dB, so you can rest assured your boiler will not be annoyingly loud, even if installed near living areas.

Intelligent boiler filling system

Like its predecessor, the Greenstar 30i, Worcester Bosch Greenstar 4000s are fitted with a software programme that automatically adjusts water levels to ensure normal boiler pressure (between 1.0 and 2.0 bar) at all times. When the boiler's pressure is low, the internal filling valve will open and fill the heating system to the correct level. If there is a significant drop in pressure, suggesting a leak in the system, you will see an error code on the boiler display.

Up to 12m flue lengths

Flue is a key element of your heating system, which ensures exhaust gases leave the system effectively and safely. The Worcester Bosch Greenstar 4000 range has longer flue lengths compared to the Greenstar i - up to 12m horizontal and vertical. This gives you more flexibility when choosing the location for your boiler.

Front access to all key components of the boiler

All of the Worcester Bosch Greenstar 4000 components are serviceable from the front, meaning you don’t need to dismount the boiler when it’s being serviced. The front cover can be easily removed by loosening two screws and removal of the right panel will provide further access, should your engineer require it.

Compatible with smart controls, including third party products

The Worcester Bosch Greenstar 4000 range is compatible with the Worcester Bosch Smart Control and products such as Nest, Tado and Hive. All these devices can be connected to your heating system via wi-fi and allow you to control your heating remotely with your phone. Smart controls come with advanced settings, where you can change the desired temperature depending on the time of day and outside weather conditions. Using such smart controls has been proven to boost your boiler's efficiency and help you save money on your energy costs.

If you are having troubles with your Worcester Bosch wireless thermostats and controls, click here for troubleshooting.

Worcester Bosch Greenstar 4000 Guarantee

For its Greenstar 4000 range, Worcester Bosch offers a generous guarantee of up to 10 years. You have the following options:

  • Standard guarantee – 7 years
  • Guarantee when a Greenstar System Filter* is fitted – 8 years
  • Guarantee when a Greenstar System Filter* is fitted, and an extra payment of £150 is made – 10 years

Worcester Bosch is one of the few manufacturers that offers a guarantee instead of a warranty. Warranties are prone to all sorts of small text which may result in engineers declining your service requests or charging you extra. Having a guarantee means that manufacturers make a promise to repair your boiler, no matter the cause.

*The Greenstar System Filters have been designed to combat the damaging effects of debris and pollutants, allowing homeowners to protect their boilers in the long run. The filters work by having high-powered internal magnets that attract and capture large amounts of waste and help your boiler stay clean and healthy for longer.

Guarantee Terms and Conditions

In order to secure the guarantee and keep it valid, you will need to ensure the following:

  1. The boiler must be installed by an official engineer that is Gas Safe certified.
  2. You or your installer must register the boiler within 30 days of the boiler installation date. You can do this by filling in a form here.
  3. The boiler must be installed in a domestic home.
  4. The boiler must be serviced by a Gas Safe engineer on an annual basis.

Give your boiler a service.

Make sure you don't invalidate your warranty. Call Smart Plan to get a boiler checkup to see if everything is in good working order.

OR 020 8146 3960

Worcester Bosch Greenstar 4000 Specifications

Width 400 mm
Height 724 mm
Depth 310 mm
Weight 34.9 kg
Fuel Type Gas
Display Type Digital
Energy Efficiency Class A
Water Efficiency Class A
Sound power 45 dB
Standard Guarantee 7 years

Still need help with your Worcester Bosch boiler?

Call Smart Plan and speak to our expert engineering team free of charge.

0333 772 6247