Worcester Greenstar Heatslave II Combi

The Worcester Bosch Greenstar Heatslave II Oil Boiler is part of Worcester Bosch’s Greenstar range. Interested in upgrading your current oil boiler? Then this review will tell you everything you need to know.

Price (Installed): From £2178 (inc. VAT)

Worcester Bosch Greenstar Heatslave II Oil Boiler Technical Specification

ManufacturerWorcester Bosch
ModelGreenstar Heatslave II Oil Boiler
Efficiency Rating90%
Energy Efficiency ClassA Rated
LPG CompatibleYes
Warranty5 years*
Central Heating Max. Output18, 25 or 32 kW
MountingFloor standing
Weight128 kg
Dimensions855mm (Height) x 520 (Width) x 600mm (Depth)

* Up to 10 years when installed by a Worcester Bosch Accredited Installer.

The Worcester Bosch Greenstar Heatslave II Oil Boiler is available in the following sizes – 18, 25 or 32kW

kWFlow Rate
1815 l/min
2518 l/min
3222 l/min

Worcester Bosch Greenstar Heatslave II Oil Boiler Key Features

  • The Greenstar Heatslave II is the UK’s most popular oil combi model
  • This is a large, floor-standing boiler that can fit underneath a standard kitchen worktop
  • This boiler is suitable for many homes, particularly properties with 2+ bathrooms and higher hot water usage
  • Holds an ‘A’ energy efficiency rating and is over 90% efficient for heat and hot water
  • Offers hot water flow rates of up to 22 litres per minute with the 32 kW model.
  • Can work with wood-fired boilers and solar panels for those looking for sustainable energy options
  • Comes with a wide variety of control options, including smart technology integration

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About the Worcester Bosch Greenstar Heatslave II Oil Boiler

  • The Worcester Bosch Greenstar Heatslave II Oil Boiler is a large model – and that size is reflected in its power and efficiency at heating and preparing hot water in domestic properties
  • As a heavy and floor-standing model, it does limit where it can be installed, but this boiler fits underneath most kitchen counters
  • Provides an effective way of heating your home if you are not connected to the gas network 
  • Part of the energy-efficient Greenstar range which has won the Which? ‘Best Buy’ award multiple times

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Our thoughts on the Worcester Bosch Greenstar Heatslave II Oil Boiler 

The Worcester Bosch Greenstar Heatslave II Oil Boiler has a smart design, with the control panel hidden from view so that it looks like a standard kitchen appliance. Offering a range of kW sizes, there is likely to be a model that is ideal for your home’s hot water and heating usage. 

A name you know

Worcester Bosch is a name you will know. The company has been offering boilers to the UK market since the 1960s. Throughout this time, they have developed an excellent reputation. However, it should be noted that the quality of some of their boilers is not what it once was.

Commitment to energy efficiency 

As it can also be used in conjunction with renewable energy sources, like solar panels and wood-fired boilers, it is a sustainable option.

All the models have a high energy efficiency rating, A rated and with above 90% efficiency. There is also an eco-hot water mode which helps to reduce energy usage and keep bills low. This function works by reducing the preheating functionality when not in use.

Aluminium heat exchanger

Whilst the energy efficiency described above is great, this won’t last forever. What you will ultimately find with the Worcester Bosch Greenstar CDi Highflow Gas Boiler is that this boiler will offer excellent heat transfer and efficiency initially. However, the efficiency will reduce, the more that the boiler is used. This is because the aluminium heat exchanger is highly susceptible to rust and corrosion which will affect efficiency.

Whilst these issues will be covered as part of the warranty, once out of warranty the repair costs for this will be costly. 

Precise control at the touch of a button

The Worcester Bosch Greenstar Heatslave II has an intuitive control panel, neatly hidden away from view in a drawer. You can also use Worcester Bosch’s EasyContol smart heating system. There will be an additional cost for this upgrade if required.

Assembled in the UK

The Worcester Bosch Greenstar Heatslave II is assembled in the Worcester Bosch production facility in Worcestershire. Whilst it is assembled here, many of the parts it is made up of are manufactured elsewhere by 3rd party companies. 

Plastic parts 

Many of the parts and components utilised within this boiler are made from plastic. This is quite a negative point as equivalent boilers at a similar price point from rival manufacturers instead use higher quality brass components.

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