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Worcester Bosch Greenstar Heatslave II External 12/18 boiler

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Plumbproud rating

75.95%

Worcester Bosch Greenstar Heatslave II External 12/18 Combi Oil boiler

We score each boiler we sell by considering a number of different factors including price installed, manufacturer guarantees, energy efficiency, the likely cost of running, and more. For this Worcester Bosch Greenstar Heatslave II External 12/18 Combi boiler, we have awarded a rating of 75.95%.

On most non-complicated installations, we would expect this Worcester Bosch Greenstar Heatslave II External 12/18 Combi boiler to cost £3,700 supplied and fully professionally installed.

For professional advice on whether the Worcester Bosch Greenstar Heatslave II External 12/18 is the right boiler for your home or to receive a free quotation, please call 01604 343053 to speak to our friendly team. You are also welcome to email us by clicking here or you can enter your postcode into the quotation box on this page.


Installed price around

£3,700

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Worcester Bosch Greenstar Heatslave II External 12/18 Combi Oil boiler frequently asked questions

Is the Worcester Bosch Greenstar Heatslave II External 12/18 boiler a combi, system or regular boiler?

The Worcester Bosch Greenstar Heatslave II External 12/18 boiler could be suitable for your house or flat if you are looking for a new combi boiler.

The UK has some of the smallest homes in the Western world, which is partly why combi boilers were introduced in the 1970s. Traditional boilers require one or more large storage tanks which they use to either heat water and keep it warm or store water intended for heating later. These tanks took up a lot of space in people's homes.

Combi boilers save space because they don't require these tanks to operate. Instead, combis draw water direct from your mains supply then instantly heat and distribute it on demand.

The biggest disadvantage in using combi boilers is that they have a maximum capacity volume for heating water. While this may not be an issue in a small household, it could be for a larger household where there is higher demand for hot water. When more than one person is using the water, it is distributed between the two points, reducing the pressure and temperature at each point.

Should I install a Worcester Bosch Greenstar Heatslave II External 12/18 combi boiler in my home?

Whether this Worcester Bosch Greenstar Heatslave II External 12/18 Combi boiler is right for where you live depends on its size or what its "output" level is. Size does not mean its physical dimensions, however - it means how powerful it is.

The output of a boiler is measured in kilowatts and indicates how much energy it can use to heat the water needed for your radiators, taps and showers. The greater the output, the more water it can heat.

A boiler whose output is too high will give you hot water and warm radiators but also higher oil bills, whereas a boiler whose output is too low will result in cheaper oil bills but the water might not always be as hot as you want it to be.

The output of the Worcester Bosch Greenstar Heatslave II External 12/18 combi is 18 kW, so which types of property would this model be appropriate for?

A PlumbProud boiler engineer would recommend that this Worcester Bosch Greenstar Heatslave II External 12/18 Combi boiler is suitable for smaller homes and apartments with up to 10 radiators and one bathroom.

When choosing a combi boiler for your home, you need to think about "flow rates" as well as output rates. This Worcester Bosch Greenstar Heatslave II External 12/18 Combi boiler's flow rate is 15 L/m.

This indicates the maximum volume of hot water (measured in litres per minute) that your boiler can heat then distribute to your taps, showers and radiators at any one time. The greater the demand for hot water in your home, the higher the flow rate you will require.

However, all combi boilers like the Worcester Bosch Greenstar Heatslave II External 12/18 draw water directly from the mains and heat it instantly.

This means that they can only heat and distribute water at the rate it enters the property (the "mains pressure" rate). For example, if your mains pressure is 11 litres per minute, this will be the highest flow rate you can achieve even if your boiler's flow rate is 17l/m.

When our engineer comes out to quote you, they may recommend that you choose a heat only boiler or system boiler instead if your family's demand for hot water is higher than normal.


The size of the Worcester Bosch Greenstar Heatslave II External 12/18

The Worcester Bosch Greenstar Heatslave II External 12/18 occupies a space of 950 mm high by 640 mm wide and 770 mm deep.

External, floor-standing combi boilers like the Worcester Bosch Greenstar Heatslave II External 12/18 don't require you to find space in your home for them and, because they're outside, you'll never hear them working unless you're out in the garden.

They provide much easier access for a heating engineer in case of a fault and their sturdy waterproof covering can handle the British climate as well as prevent rusting and water ingress.

Other benefits include the fact that gas will disperse into the atmosphere outdoors in the event of a carbon monoxide leak. The chances of an oil leak damaging your property are also greatly reduced because the boiler is not installed inside your property.

Is the Worcester Bosch Greenstar Heatslave II External 12/18 non-condensing or condensing?

The Worcester Bosch Greenstar Heatslave II External 12/18 is a condensing oil boiler - this is the type of boiler we recommend to most clients because they're better for the environment and they will save money on annual fuel bills.

A condensing boiler captures and recycles the warmth still present in both the flue exhaust gases and water vapour condensation created when oil is burned to provide your boiler with power.

This means it needs less oil to operate and it uses this extra energy to perform a number of tasks, including heating the colder water that comes back to the boiler from the radiators in your home.

Is the Worcester Bosch Greenstar Heatslave II External 12/18 combi good for the environment?

Many homeowners are becoming increasingly concerned about how they heat their homes and the impact it has on climate change and other important environmental issues.

In the UK, central heating is responsible for 14% of greenhouse gas production. Domestic gas boilers emit large quantities of nitrogen dioxide in British cities.

Is the Worcester Bosch Greenstar Heatslave II External 12/18 combi boiler an environmentally friendly choice for your home? Here’s what the figures say.

The energy efficiency rating for a boiler describes the amount of energy it uses and wastes during operation and there are two different ways to measure it.

All boilers manufactured and supplied in the UK must have a SEDBUK rating of “A” subject to a minimum energy efficiency score of 92% or above. Before April 2018, the minimum energy efficiency score was 88% (88/89% = "B" SEDBUK rating, 90%+ = "A" SEDBUK rating).

The Worcester Bosch Greenstar Heatslave II External 12/18 scored an efficiency rating of 90% and a SEDBUK band rating of A.

The Energy Related Products Directive (ERP) is European legislation that applies to all products which use or consume energy during their lifespan, including during the manufacturing process and when they're in actual use, right through to the point of final disposal.

The aim is to encourage manufacturers to create new products that are kinder to the environment and create fewer harmful gas emissions.

The Worcester Bosch Greenstar Heatslave II External 12/18 has an ERP Heat rating of "A" and an ERP Water rating of "B".

How many years' warranty does the Worcester Bosch Greenstar Heatslave II External 12/18 combi come with?

The parts and labour warranty on the Worcester Bosch Greenstar Heatslave II External 12/18 covers all repair-related costs for 2 years while the heat exchange warranty covers you for [Heat Exchange Warranty] years.


Worcester Bosch Greenstar Heatslave II External 12/18 Oil Combi boiler specifications

Powered by GasOil
LocationExternal
Condensing?Yes
Efficiency rating90%
Band ratingA
LPG Compatible?No
P/L Warranty2 Years
Output in kW18 kW
Height950 mm
Width640 mm
Depth770 mm
MountingFloor
Flow rate15 L/m
ERP HeatA
ERP WaterB

The top 10 rated Oil Combi boilers

Using the Plumbproud scoring system, the current 10 ten Oil Combi boilers assessed using a number of important variables are as follows:

1Worcester Bosch Greenstar Heatslave II 12/1876.19%
2Worcester Bosch Greenstar Heatslave II 18/2576.12%
3Worcester Bosch Greenstar Heatslave II External 12/1875.95%
4Worcester Bosch Greenstar Heatslave II 25/3275.83%
5Worcester Bosch Greenstar Heatslave II External 25/3275.58%
6Grant Vortex Pro 2167.46%
7Grant Vortex Pro 2667.43%
8Grant Vortex Pro 26kW67.35%
9Grant Vortex Pro 2167.31%
10Grant Vortex Pro 2667.14%

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Worcester Bosch Greenstar Heatslave II External 12/18 boiler

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Worcester Bosch Greenstar Heatslave II External 12/18 Combi Oil boiler

  1. Home
  2. Worcester Bosch Greenstar Heatslave II External 12/18
Plumbproud rating for this boiler
75.95%

Using factors such as price installed, manufacturer guarantees, energy efficiency and the likely cost of running, among others, this model has been rated as scoring 75.95% on the PlumbProud boiler benchmarking system.

On most non-complicated installations, we would expect this Worcester Bosch Greenstar Heatslave II External 12/18 Combi boiler to cost £3,700 supplied and fully professionally installed.

You can speak to our friendly and professional advisors by calling 01604 343053. They can provide you with a free quotation on the Worcester Bosch Greenstar Heatslave II External 12/18 boiler and confirm that it is suitable for your home. You can also click here to email us or enter your postcode into the quotation box on this page.


Installed price guideline
£3,700

Get your free quote

Worcester Bosch Greenstar Heatslave II External 12/18 Oil Combi boiler specifications

Powered by GasOil
LocationExternal
Condensing?Yes
Efficiency rating90%
Band ratingA
LPG Compatible?No
P/L Warranty2 Years
Output in kW18 kW
Height950 mm
Width640 mm
Depth770 mm
MountingFloor
Flow rate15 L/m
ERP HeatA
ERP WaterB

Worcester Bosch Greenstar Heatslave II External 12/18 Combi Oil boiler frequently asked questions

Is the Worcester Bosch Greenstar Heatslave II External 12/18 a combi boiler, system boiler or regular boiler?

The Worcester Bosch Greenstar Heatslave II External 12/18 is worthy of consideration if you're looking for a combi boiler for your flat or house.

Combi boilers provide hot water or heating for your home on demand. You just need to turn the tap to get hot water or switch on the radiator and you’ll feel your home warm up within minutes.

In contrast, traditional boilers required either one or two large storage tanks to work - one to heat and keep water warm and the other to hold cold water for later heating. If the immersion tank was empty, it wasn’t uncommon to wait up to an hour for enough hot water to fill a bath, for example.

Combi boilers draw cold water from the mains and then heat it instantly whenever it's needed, all from one small unit.

The one disadvantage to combi boilers is that, if more than one point is in use at any one time (for example, if someone is taking a shower and another person turns on a hot water tap elsewhere in the property), water pressure, temperature and volume drop to both points.

Is a Worcester Bosch Greenstar Heatslave II External 12/18 combi boiler suitable for my house or flat?

Selecting the right boiler for your property means selecting a boiler that is the right size. And, by size, we don't mean how big it is, we mean how powerful it is - the "output".

The output of a boiler is measured in kilowatts. The output level determines the maximum power a boiler can use in heating the water needed for the baths, showers, taps and radiators in your home.

It's important to choose a boiler with an appropriate level of output for your property. Your boiler should be able to cope with periods of peak demand in your property and not just your average usage.

An output rate that is too low will result in an inadequate supply of hot water, while an output that is too high will mean the boiler will cost more to run than is necessary.

The output of the Worcester Bosch Greenstar Heatslave II External 12/18 combi is 18 kW kilowatts, so which types of property would this be appropriate for?

Most experienced boiler engineers would recommend this Worcester Bosch Greenstar Heatslave II External 12/18 Combi boiler as a suitable option for smaller homes and apartments with no more than up to 10 radiators and one bathroom.

With combi boilers, you need to consider the flow rate as well as the output rate. The flow rate (shown in litres per minute) measures how much water your boiler can draw from the mains which it then instantly heats and distributes to your taps and radiators.

However, a high flow rate is of little to no value if your local water pressure is low. If your local mains water pressure is 10l/m and your flow rate is 12l/m, your boiler will only be able to process 10l/m.

If you live in an area with high water pressure but your household has multiple bathrooms and/or radiators and many members of your household want to use hot water at the same time (like morning or evening baths or showers), it's unlikely that you'll be able to find a combi with a high enough flow rate.

As an indication, a power shower needs about 10 litres of water per minute, whereas the flow rate of this Worcester Bosch Greenstar Heatslave II External 12/18 Combi boiler is 15 L/ml/m.

When our engineer comes out to quote you, they may recommend that you choose a heat only boiler or system boiler instead if your family's demand for hot water is higher than normal.


How large is the Worcester Bosch Greenstar Heatslave II External 12/18?

The Worcester Bosch Greenstar Heatslave II External 12/18 is 950 mm tall, 640 mm wide, and 770 mm deep.

Floor-standing external combi boilers like the Worcester Bosch Greenstar Heatslave II External 12/18 operate reliably and consistently outdoors because of their solid weatherproof housing designed to protect against rusting and water ingress. And, because they're not installed inside your property, you save valuable indoor space.

Internal oil boilers can leak and, when they do, they damage your property and leave unpleasant odours which are hard to remove. An external boiler eliminates the risk of indoor oil leaks and the danger of carbon monoxide getting into your home is also greatly reduced. An external boiler is easier for your heating engineer to access when it requires servicing or repair.

Is the Worcester Bosch Greenstar Heatslave II External 12/18 condensing or non-condensing?

We recommend that, if possible, you choose a condensing boiler like the Worcester Bosch Greenstar Heatslave II External 12/18.

Condensing boilers are more energy-efficient. They achieve this efficiency by capturing the heat present in flue exhaust gases and water vapour condensation and recycling that heat to, for example, warm colder water coming back from your radiators.

By choosing the latest condensing boiler, you'll also notice a significant reduction in your oil bills, particularly if you're replacing a boiler more than 15 years old.

Is the Worcester Bosch Greenstar Heatslave II External 12/18 combi boiler environmentally friendly?

How we heat our homes is an issue which many homeowners worry about as the world combats climate change and environmental damage.

In the UK, central heating is responsible for 14% of greenhouse gas production. Domestic gas boilers emit large quantities of nitrogen dioxide in British cities.

If you would like your next boiler to help in the fight against climate change, would the Worcester Bosch Greenstar Heatslave II External 12/18 combi be a suitable choice?

The energy efficiency rating of the Worcester Bosch Greenstar Heatslave II External 12/18 is 90% with a SEDBUK band rating of "A".

Energy efficiency tests record how much energy is wasted on non-core functions during an operation.

By law, all boilers manufactured and supplied in the UK must have a minimum energy efficiency performance level of 92% (equivalent to a SEDBUK "A" grade). Up to April 2018, the minimum performance level was 88% (88% and 89% are equivalent to a SEDBUK "B" grade and 90%+ an "A" grade).

The Energy Related Products Directive (ERP) came into force in 2015. This legislation was introduced to encourage manufacturers to create more energy-efficient products and it covers all products that consume energy during their lifetimes, including energy used during production and at the point of disposal.

ERP ratings of "A" for heat and "B" for water were assigned when testing the Worcester Bosch Greenstar Heatslave II External 12/18.

What is the warranty period on a Worcester Bosch Greenstar Heatslave II External 12/18 combi boiler?

A parts and labour warranty of 2 years is included with the Worcester Bosch Worcester Bosch Greenstar Heatslave II External 12/18 boiler.


The top 10 rated Oil Combi boilers

Using the Plumbproud scoring system, the current 10 ten Oil Combi boilers assessed using a number of important variables are as follows:

1Worcester Bosch Greenstar Heatslave II 12/1876.19%
2Worcester Bosch Greenstar Heatslave II 18/2576.12%
3Worcester Bosch Greenstar Heatslave II External 12/1875.95%
4Worcester Bosch Greenstar Heatslave II 25/3275.83%
5Worcester Bosch Greenstar Heatslave II External 25/3275.58%
6Grant Vortex Pro 2167.46%
7Grant Vortex Pro 2667.43%
8Grant Vortex Pro 26kW67.35%
9Grant Vortex Pro 2167.31%
10Grant Vortex Pro 2667.14%
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