The Greenstar Heatslave II External is designed for homeowners who prefer to keep their boiler outside and properties without enough interior space.

It’s a floor standing oil-fired combi boiler, meaning you do not need a cold water tank or hot water cylinder in order for this boiler to provide you with heating and hot water. Three hot water flow rates and outputs are available including 15 litres per minute for the 18kW unit, 18 litres for the 25kW model and 22 litres for the 32kW version, all of which measure 950mm (H) x 640mm (W) x 770mm (D).

This series has options for small, medium and large-sized homes with one or two bathrooms and the boiler will come with a 2-year warranty, regardless of which output level you choose. When it comes to price, you can expect to pay anything between £2,403 and £2,727 on a new Greenstar Heatslave II External boiler.

Boiler Energy Efficiency Credentials

Relaunched in 2015, the Greenstar Heatslave II External is more energy efficient than ever before and has an official efficiency rating of 90%. It is, in fact, A rated for heat, B rated for water and fully compliant with the latest ErP (Energy-related Products) Directive. The boiler comes with an energy-saving ECO mode that makes the burner fire less frequently between demands whilst maintaining the heat store temperature at a lower level and ensuring the hot water set point that you have entered remains the same. It is also compatible with a range of optional controls and can accept water heated by green sources such as wood-fired boilers and solar energy for increased efficiency and lower fuel bills.

Greenstar Heatslave II External Technology and Main Advantages

This model by Worcester Bosch has its own thermal store (small tank) that contains the same water found in your radiators and can instantly heat cold water, then pass the heated water to your showers and hot water taps. It also features a ‘keep hot’ facility to ensure hot water is instantly available as and when you need it.

The boiler itself is contained within a robust cabinet to safeguard the appliance from dust, water and external elements – keeping it fully protected whatever the weather. This special cabinet is green powder coated so that it blends in with your outdoor area and garden plants. Also, the boiler features a built-in frost thermostat to protect it from freezing during the colder months of the year.

All of the boiler controls are concealed in a slide open drawer to stop your young children fiddling with control knobs, and the pull-out interface allows you to precisely manage your heating and hot water. The interface also enables you to attach an optional comfort or intelligent control for added comfort and energy savings.

Is the Greenstar Heatslave II External the Right Boiler Type and Size for Your Home?

By being available in a range of outputs, the Greenstar Heatslave II External is suited to small and medium properties, as well as larger homes with two bathrooms. As this boiler is a combi, it does not require the use of traditional tanks or cylinders and is ideal for houses without access to a mains gas supply. But before you purchase this model, you must seek advice from a Gas Safe registered engineer to be sure it can comfortably heat your home and provide you with enough hot water.