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Worcester Bosch Greenstar 4000 System Boiler

Replacing the top-selling Greenstar i, the Worcester Bosch Greenstar 4000 System is instantly familiar and comes with added features.  

The Worcester Bosch Greenstar 4000 System builds upon the much-loved features of the Greenstar i but is more attractive and receives upgrades to its performance. It has a wide power range to help reduce gas consumption and your energy bills, plus it can run on a mixture of hydrogen and natural gas and be used with Greenskies solar panels for energy and cost savings. This system boiler is also easy to live with because it’s among the quietest on the market. 

How Much Does this Boiler Cost?

This system boiler from Worcester Bosch is available with 12kW, 15kW, 18kW, 21kW and 24kW outputs to suit your requirements and costs between £960 and £1,120, not including installation. System boiler installation costs can vary a lot, so we recommend getting a quote from different local and national installers to find the best price. Make sure you only request quotes from Gas Safe registered installers who are qualified to work legally on gas boilers. 

How will I know if this Boiler is Suitable for My Home?

Worcester Bosch’s Greenstar 4000 System boiler is suitable for small and medium-sized homes with more than one bathroom and enough space for a hot water storage cylinder, usually located in an airing cupboard. System boilers, such as this one, don’t require tanks in the loft and are compatible with solar water heating systems. 

If you’re unsure whether a system boiler is a good fit for your home, we suggest you consult a qualified heating engineer. In addition to advising you on the correct boiler type for your home, they can help you work out what boiler size will meet all of your needs. 

Is it a High Efficiency Boiler?

It is. The Worcester Bosch Greenstar 4000 System boiler is A-rated and scores 94% for efficiency, meaning it will play its part in lowering your carbon footprint and reducing your heating bills. 

Does this Boiler have a Good Range of Controls and Features?

This system boiler from Worcester Bosch has an easy-to-use colour display with push-button controls and can be controlled wirelessly with the optional Bosch EasyControl smart thermostat that lets you track your energy usage and manage your heating and hot water. Worcester Bosch says the Greenstar 4000 System is its quietest system boiler with easy to access components to save time during servicing and maintenance. It comes in 100% planet-friendly packaging, can run on 20% hydrogen and works with Greenskies solar panels to maximise energy and cost savings.  

How long is the Warranty on this Boiler?

The Worcester Bosch Greenstar 4000 System boiler comes with a 5-year warranty as standard, which can be extended to 10 years when installed by a Worcester Bosch Accredited Installer. 

Summary of Important Information

  • Expect to pay between £960 and £1,120
  • Heating output of 12kW, 15kW, 18kW, 21kW or 24kW
  • Dimensions of 724mm (H) x 400mm (W) x 310mm (D)
  • Uses gas as its fuel source
  • A-rated for efficiency
  • Smart compatible
  • 5-year warranty as standard

Pros and Cons

The Greenstar 4000 System boiler keeps everything people love about the Greenstar I, but is quieter, more energy-efficient and a better performing boiler than its predecessor. It also has a high-tech control system to make life easier for owners. But keep in mind that this system boiler is only suitable for homes with a heating system that includes a hot water storage cylinder. 


  • Awarded Which? Best Buy
  • Worcester Bosch has a Which? brand score of 84% – correct at the time of writing – January 2022
  • Suited to small and medium-sized homes 
  • Easy-to-use push-button LCD display
  • One of Worcester Bosch’s quietest boilers to date
  • 100% planet-friendly packaging
  • No need for separate loft tanks
  • Compatible with Bosch EasyControl – can tailor hot water times and heating temperatures from your smartphone or tablet, even when you’re not at home
  • Solar compatible – greater energy and cost savings
  • Provides maximum energy efficiency – reduce fuel bills and carbon emissions
  • Excellent rating on Trustpilot – correct at the time of writing – January 2022


  • Requires separate cylinder
  • 5-year warranty – but this can be extended to 10 years
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