• Get the best quotes, fast!
  • Over 5,000 engineers across the UK
  • Gas Safe registered engineers

Need a new boiler?

Get FREE no-obligation quotes now!

  • No delays! Get quotes today
  • Compare quotes & get the best prices
  • Gas Safe & OFTEC registered engineers
 4.8 stars

1,216 reviews

 4.8 stars

1,216 reviews

Worcester Bosch vs Grant Oil Boiler Comparison

Looking for a new oil Combi boiler? Worcester Bosch and Grant are two of the most well known and highly trusted brands you will find. But is there a winner between the two? We’ve compared an oil Combi boiler from each brand to help you decide.

No to gas boilers

Get Boiler Quotes

If it’s time to replace your current boiler, use our free service to get quotes now


Brand Introduction

When it comes to oil boilers, Grant and Worcester Bosch are undoubtedly the leading manufacturers in the 2017 market. Both brands have been manufacturing heating products for decades and are, as they always have been, based in England. The reputation of each brand is impressive; both regularly top consumer and engineer surveys and opinion polls.

Grant have specialised in producing high efficiency condensing boilers for over 10 years and today the range features 60 different oil boilers between 12-70kW including internal and external models. In addition to their oil fired models the company is committed to helping homeowners to lower their carbon footprint and heat their homes more efficiently. They are doing this by developing innovative technology, enabling their customers to incorporate renewable energy sources such as solar or biomass into their oil heating system.

Worcester Bosch have been established since 1962 and currently manufactures 30 oil-fired boilers including internal and external models. While originally an independent company simply called ‘Worcester’ it has since been bought by Bosch, a multinational engineering and technology company. Worcester manufacture a wide range of boilers including gas and LPG as well as oil.

Comparing a Boiler

To make an accurate comparison in terms of performance we need to compare a boiler from each brand which is comparable in size: Grant VortexBlue and the Worcester Bosch Greenstar Heatslave II.

These floor standing boilers are for internal installation and are recommended for flats or small houses with up to 2 bathrooms and 10 radiators. Both boilers can be used in conjunction with renewable energy sources like solar energy and biomass so you can reduce your reliance on oil.

Boiler Make / Model Grant VortexBlue Combi Oil Boiler 26kW Worcester Bosch Greenstar Heatslave II Combi Oil Boiler 25kW
Dimensions (HxWxD) 860 x 614 x 606mm 855 x 520 x 600mm
Energy Efficiency Class (Heat) A/td> A
Energy Efficiency Class (Heat) B B
Seasonal Space Heating Efficiency 91.71% 90%
Useful Efficiency at rated heat output & high temperature regime 93.6% 90.9%
Useful Efficiency at 30% of rated heat output & low temperature regime 96.4% 95.8%
Noise Level Output (dB) 50.6 56
External Model Available Yes Yes
Warranty Heat Exchanger: 10 years (when installed by a Grant accredited installer)
All other parts & labour: 2 years
Heat Exchanger: 10 years (when installed by a Worcester Bosch accredited installer)
All other parts & labour: 2 years
LPG Convertible No No
Notable Features 24ltr expansion vessel
Neon diagnostic indicators
Factory-fitted internal condensate trap (which can be sited externally)
Eco hot water mode
Compatible with a range of optional controls
Other Outputs Available 21kW, 36kW 18kW, 32kW

Get Boiler Quotes

If it’s time to replace your current boiler, use our free service to get quotes now


Alternatively you can compare up to 4 different boiler models via our Comparison Tool.

The key difference between the two boilers lies in the energy efficiency levels. Grant comes out on top in this area and, while the difference isn’t overwhelming, with so little else to tell the boilers apart this could be a deciding factor. Their improved efficiency over the Worcester Bosch model could be down to Grant’s award winning stainless steel heat exchanger which has a larger surface area and low water content to improve the hot water performance of the boiler.

The Grant boiler also incorporates a low pressure cut-off switch which means the boiler will shut down should it sense water loss. The “unique turbulator baffle system” system extracts the latent heat usually lost through the flue to be reused in the system. This recycled energy means the boiler can work even more efficiently which will mean you have lower energy bills.   The Grant boiler utilises the latest Riello RDB Blu burner technology and also has a lower operating noise level than the Worcester Bosch boiler.


Worcester Bosch also offer a wide range of controls and thermostats for their boilers including their own smartcontrol system called ‘Wave’. Wave enables you to manage your heating and hot water from an internet connected smart device. This enables you to track your energy usage and identify areas where you could save money on your energy bills.

Grant also offers a range of controls and tools to help you improve your energy efficiency such as intelligent weather compensation via sensors but does not yet offer an internet connected system.


In general, you can find a from both Worcester Bosch and Grant for between £1,200 and £2,500, depending on their size and type.

In the case of the oil Combi boilers we’ve compared here, however, our research found the Grant boiler to be the pricier option at around £2,570 with the Worcester Bosch model costing slightly less at £2,280 (on average).

Repairs & Warranties

The best course of action is to get your oil boiler installed by a manufacturer accredited engineer. This means not only that you can rest assured your boiler has been installed correctly but will also extend the warranty you receive significantly. If this is the case both manufacturers offer a 10 year guarantee on the heat exchanger which is the crucial component that actually heats the water for your home. The warranty on the rest of the parts and labour will vary so it’s important to check your guarantee information carefully. Remember to register your product with the manufacturer as soon as possible after installation to ensure you’re entitled to the full warranty period.

As with all oil boilers it’s really important to get it serviced annually by a fully qualified and OFTEC registered engineer. This means your boiler will continue to operate at optimum efficiency and is usually a condition of your warranty. The Grant boiler has been designed with easy maintenance and servicing in mind and has front access to all the serviceable parts.

If a fault occurs within your guarantee period you should contact your installer in the first instance so they can rule out issues with other parts of your heating system such as running out of oil, blocked radiators, frozen pipes etc. If the fault is found to be with the boiler itself it will be repaired free of charge by both manufacturers if all terms and conditions of the warranty have been met.

So, is there a winner?

Grant has invested significantly in the technology included in their boilers and as a result, their VortexBlue Combi offers slightly better efficiency levels and a quieter operating noise.

However, it’s worth noting that you may end up paying a higher price for a Grant boiler than a Worcester Bosch. If the slight differences in efficiency levels are not as important to you as your budget, Worcester Bosch are undoubtedly still a reliable and high quality choice with a slightly lower price tag. In addition, if internet connected smart controls are of interest to you, the ‘Wave’ system and app by Worcester Bosch may tip the scales a little further towards Worcester.

Get Boiler Quotes

If it’s time to replace your current boiler, use our free service to get quotes now


Need a new boiler?

Get FREE no-obligation quotes now!

Excellent 4.8 out of 5
Excellent 4.8 out of 5

Find local heating engineers

Find approved boiler engineers
in your area.

Begin your search by entering your postcode below.