Grant vs Worcester Bosch

Grant vs Worcester Bosch

Grant vs Worcester Bosch – Battle of the Two Best Oil Boilers in the UK

When you’re living off the mains-gas grid, whether you’re in an urban or a rural area, Grant vs Worcester Bosch are the two best oil boilers money can buy.  We take a look at both brands, compare their best selling oil boiler models, and look at the pros and cons in detail.

Oil Boilers

About 4 million households are not connected to the UK’s gas network.  For these homes living off the Mains Gas grid, Oil and LPG are the two best fuels to power a central heating system.  However, oil is a more energy efficient and cost effective fuel compared to LPG to run your central heating system on.  While there’s not an overwhelming option in the current market for oil boilers, you still have a good range to choose from when upgrading your oil heating system.  Grant vs Worcester Bosch are the two best and biggest manufacturers of oil boilers in the UK.  Let’s take a closer look at each brand:

best oil boilers 2018, grant oil boilers

Grant Engineering have been designing and manufacturing heating products for four decades now.  Their range of oil-fired condensing boilers are very highly reviewed and heavily favored above other brands by reputed review magazines and websites.  Grant’s oil-fired condensing boilers range have a reputation for quality and reliability, on top of being easy to install and maintain.  The Grant Vortex and VortexBlue oil boiler ranges are trusted by engineers and householders all over the UK.  In 2016, Grant sold more Vortex and VortexBlue oil condensing boilers than any other oil boiler brand in the UK (source: EUA).  And this year, in a 2017 Boiler Survey done by a prominent review magazine in the UK, all of Grant’s oil boilers were awarded a “Best Buy” award.  You can find more information on that by clicking this link – Grant awarded Best Buy Boiler


Grant has a wide variety of 63 oil boilers, consisting of internal, external, system, boiler house, wall hung, and combi variants.  Consequently, Grant has an oil boiler solution for almost any domestic property’s heating needs.  This kind of extended range of oil boilers wasn’t available to off-grid residents some years ago.  But now, with so much choice on offer throughout the Vortex and VortexBlue ranges, Grant oil boilers have established themselves as market leaders.  One of the best selling oil boiler from Grant Engineering is:

Grant Vortex Pro 26 Floor Standing Combination Oil Boiler

Grant vs Worcester Bosch, Grant Vortex Pro

Grant Vortex Pro 26

Grant’s Vortex oil boilers have some of the highest efficiencies available in the UK, achieving gross seasonal efficiencies of up to 93.3% (SAP 2009).  The range is available with heating outputs from 12kW up to 70kW.  Grant  have got a wide range of oil boilers which suit all types of houses, whether white cased utility internal models or powder coated external models, to wall hung boilers, to the red cased boiler house models.  Below are some of their key features:

  • ErP ‘A’ rated.
  • Slimline models available including the Vortex Utility 15-21kW which is only 348mm wide, and the Vortex Combi XS which is 515mm wide.
  • All Vortex and VortexBlue Combis come with a 24ltr expansion vessel as standard.
  • All of Grant’s oil boilers incorporate their patented stainless steel heat exchanger technology which ensure each product is highly efficient.
  • VortexBlue models have same dimensions as Vortex equivalents so ideal for replacement boiler installations.
  • All Vortex oil boilers are available with a 7 year guarantee when installed and registered by Boiler Hut Ltd (subject to T&Cs).
  • All VortexBlue oil boilers are available with a 10 year guarantee when installed and registered by Boiler Hut Ltd (subject to T&Cs).

best oil boilers, worcester bosch oil boilers

Worcester Bosch were established in 1962 by Cecil Duckworth as Worcester Engineering Co Ltd.  Bosch acquired it in 1992, hence the name of the company today, i.e. Worcester Bosch.  Their current range of oil-fired boilers is around 30, and that includes internal and external models.  They manufacture a wide range of boilers, including gas and LPG, as well as oil.

Their best selling oil boiler is:

Worcester Greenstar Heatslave II Oil Combination Boiler

Grant vs Worcester Bosch, Worcester Bosch Greenstar Heatslave II

Suitable for small, medium and large sized properties, this boiler features easy access connections and a one piece stainless steel primary baffle and cross firing burner. The next generation Heatronic 4i digital control unit provides accurate control and diagnostic information.

  • Cross firing burner.
  • One piece baffle for quick and easy servicing.
  • Easy access oil and hydraulic connections.
  • Digital control offering precision heating and hot water control.
  • Lightweight aiding installation.
  • Front access for routine servicing, including a pivoting expansion vessel for ease of access.
  • Compatible with our Greenstar Comfort controls.
  • Compatible with solar thermal.
  • 5 year guarantee on Worcester primary heat exchanger.
  • 80/125mm room sealed flues with lengths of up to 8m available.
  • Plume management of up to 5m with conventional and flexi-flue kits also available

Grant vs Worcester Bosch Comparison

As pictured and described above, the two comparable boilers for Grant vs Worcester Bosch, in terms of performance, are Grant Vortex Pro and Worcester Bosch Greenstar Heatslave II.  Both these boilers are floor standing boilers meant for internal installation.  These boilers are recommended for small houses or apartments with about 10 radiators and 2 bathrooms.  They can also use renewable energy sources like solar energy and biomass, so you don’t have to depend entirely on oil to heat your home.  Below is a side by side comparison sheet for both boilers.

grant vs worcester bosch review


Grant vs Worcester Bosch – Price

*Please note, the prices given below are for boilers only.  The final price for a boiler installation will include labour costs, extras like chemical flush, magnetic and limescale filters, and thermostats etc.

Worcester Greenstar Heatslave II 18/25 Combination Boiler Oil – £2,320.96

Grant Vortex Pro 26 Floor Standing Combination Boiler Oil – £2,293.40

Although the difference is negligible, the Grant boiler is still the clear winner here.  Let me explain why.  Not only is it more energy efficient, it’s also got a stainless steel heat exchanger compared with aluminium in Worcester Bosch.  Stainless steel is more durable and highly corrosion resistant, which is why manufacturers using them (Viessmann and Grant) can offer longer warranties.  Keeping that in mind, the Grant oil boiler is amazing value for your money.

Grant vs Worcester Bosch – Energy Efficiency

Grant vs Worcester Bosch, Energy Efficiency

With threats like Global Warming and Climate Change looming, energy efficiency has been a major talking point for years now.  Especially with modern condensing boilers now running at almost 94% efficiency.  Installing a high efficiency boiler not only saves you money on energy bills, it helps you leave a smaller carbon footprint.  You are being kinder to the planet.  Grant beats Worcester Bosch in this area, but only slightly, with 93.6% efficiency for the Grant oil boiler compared to 90.9% for the Worcester.  Even though the difference isn’t massive, with all boilers in the market today so evenly matched, even slight edge can make a difference.  You do want to buy the best product possible for the money.  Grant’s higher energy efficiency is down to their award-winning stainless steel heat exchanger with a larger surface area and low water content to improve the hot water performance of the boiler.  Grant boilers also have a low pressure cut-off switch, so the boiler will shut down if there’s water loss.  There’s another feature unique to Grant boilers, which is the turbulator baffle system, which extracts the latent heat usually lost through the flue to be reused in the system.  The recycled and reusable energy means higher energy efficiency for the boiler, which translates to even lower energy bills.  And since both boilers cost pretty much the same, the Grant boiler with all these additional features is a steal!

FREE Boiler Grants from Gov.UK – You may be eligible

If you’re on certain qualifying benefits like:

  • Pension Guarantee Credit.
  • CTC/WTC.
  • Income Related ESA.
  • Income Based JSA.
  • Pension Guarantee Credits.
  • Income Support.
  • Universal Credits.

The UK Government offers a free boiler grant under the ECO (Energy Company Obligation) Scheme.  There’s additional funding available, especially if your current boiler runs on Oil or LPG, and is more than 8-10 years old.  Depending on your property’s carbon score, you may get the boiler completely free.  More information on the FREE boiler grants on the official website below:

OFGEM.Gov.UK – About the ECO Scheme

If you would like to check whether you qualify or to apply online, please click the link below:

FREE Oil Boiler Grants – Apply Online

Grant vs Worcester Bosch – How can Boilerhut help you?

Grant vs Worcester Bosch, Grant Accredited Installers

Our job is to give you unbiased information.  The Grant oil boiler has come out on top in many independent reviews.  The fact that Boilerhut are Grant Approved Installers doesn’t factor into our recommendation.  We wouldn’t recommend a sub-standard product.  Furthermore, because of the long term reliability and durability of Grant Oil Boilers, you get extended 7 year parts and labour warranty, and the same on their stainless steel heat exchanger.  If you were to buy the boiler yourself and get it installed by a local plumber, you will only get a 2 year warranty.

The extended warranties you get through Boilerhut are the same whether you’re paying for the boiler outright or getting it for free or part-funded through the government grant.  You can get a free online quote by putting your postcode below and hitting the green button.

Please note, once you put your details in, what you will get is an online estimate, and not the final quote.  Depending on how difficult the job is, flue choices, gas upgrades etc. our firm and final quote will be lower.  Once you’ve gone through the quoting process, one of our team members will get in touch with you and discuss your final quote.

2 replies
  1. J Fry
    J Fry says:

    Great review. I’m replacing a Grant oil boiler (utility model installed in basement) – which served us well for nearly 11 years, but had intermittent problems last winter. Own fault as not had regular services. Lesson learned! Technology has moved on and it seems the time has come for a new boiler. Haven’t made up my mind to stay with Grant or go with WB. The size of the boiler I have now is 15-26, but I’ve never been sure if that was the best size for us. I see that the number of rooms seems to be the most common method of determining the size needed, but I’m thinking using heat loss figures might be more accurate. I have very carefully calculated and checked the heat loss figures for each room/area of my large bungalow. The total heat loss of the property is 13380W. I believe it is normal to add 20% to that figure to determine the size of boiler required (?) but have not done so here. So my question is, using the total heat loss figure, can you say what size boiler I need? OR is number of rooms the best way to decide? I should mention that there are 15 radiators in the house though NEVER all used at the same time. There are 12 rooms including hall, kitchens, bathroom. Many thanks if you can advise.

    • Ashish Sebastian
      Ashish Sebastian says:

      Dear Mr. Fry,

      Thanks for your comment. Please see reply from our oil heating expert Bernard below:

      1. As a rule of thumb we allow 1.2Kw per radiator or towel rail, however towel rails seldom are above 0.5kw Bed rads below 1kw Lounge rads max 2kw.
      2. It is important not to oversize or undersize a boiler, so 15 x 1.2kw = 18kw max & a small allowance for hot water = Grant Pro vortex VTX15/21.
      3. Your heat calculation loss for the building is approx 13.4kw correctly. Add a 20% = 16.08kw, this factor is purely added for optimum start from cold.
      4. The fact that all radiators are not in use at the same time should no be considered and the following recommendations are very important:

    • Boiler & complete system should be chemically flushed & a magnetic system filter Installed [ this alone will affect the performance and warranty if not adhered to ].
    • Thermostatic radiator valves should be fitted to all radiators except where the room thermostat resides [ Energy saving & optimum comfort levels ]
    • All attic pipe work should be suitably Insulated [ Energy saving & frost protection ]
    • A programmable room thermostat should be fitted [ To comply with building regulations & aids efficiency as this is the only Component that shuts the boiler down ]
    • We have recommended a Grant Vortex 15/21 utility boiler as a replacement however if the radiators are currently over sized [ quite common ] then choose a VTX15/26.

      If you would like a free, no obligation oil boiler quote, you may do so by clicking this link –

      Best regards,
      Boilerhut Ltd


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