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7 July 2021

Grant oil boilers rated

We take a close look at the the oil boilers manufactured by Grant boilers. Find out more about Grant oil boilers
Matthew Knight

Grant Engineering has been designing, manufacturing and supplying heating products for over four decades. Their manufacturing plant is based in Birr in Co Offaly with the Grant UK Head Office based in Devizes, Wiltshire. One of its core objectives is to provide environmentally friendly, sustainable and reliable heating solutions to help homeowners reduce their energy bills and lower their carbon footprint.

Grant is largely known for its oil boilers but its expanding product portfolio is making it easier for homeowners to install renewable technologies into their homes, whether that be with air source heat pumps or hybrid technologies which combine greener energy into traditional oil-fired home heating systems.

Grant produces two main ranges of oil-fired boilers - the Vortex and VortexBlue – totalling sixty-three different models across both ranges. Both come in a variety of specifications to give you flexibility over where they can be installed. The Vortex range consists of internal, external, combi, wall hung and boiler house variants with outputs ranging from 12kW up to 70kW. This includes the Vortex Pro range of kitchen/utility models and external boilers which are available in heat outputs to cater for all sizes of home. Most models are heat-only and can be converted into system boilers, but system boilers are available too.

The VortexBlue oil boilers incorporate the latest ultra-low NOx burner technology helping householders to further lower their emissions. This range includes internal, external and combi boilers and are available in outputs of 15kW up to 36kW. These floor standing boilers are ideal for kitchen and utility rooms (internal models) or, when space is at a premium, can be sited outdoors (external models).

You can find more details about the individual products in these ranges in our boiler reviews.

Which? verdict on Grant oil boilers

Here, you'll find all of our survey results for Grant oil boilers, including how reliable they are and whether Grant oil boiler owners would recommend their boiler.

The reliability and customer score are based on responses from a May and June 2020 survey of 7,500 boiler owners.Engineer recommendation, build quality, availability of parts and spares, and ease of fixing a common fault and ease of servicing are based on responses to a June 2020 survey of 153 Which? Trusted Traders heating engineers.

Which? members can log in to see what owners and engineers make of Grant oil boilers in the table below. If you're not already a member, try Which? today.

Overall score
Customer score
Fixing a common fault
Ease of sourcing parts

How much do Grant oil boilers cost?

Grant boilers cost between £1,180 and £2,380, depending on their size and type. 

Choosing the best Grant oil boilers

You can have a Grant oil boiler installed by a registered Grant boiler engineer. The best way to find an engineer is by getting in touch with Grant UK using the contact details below. 

Grant warranties and servicing

The heat exchanger on Grant Vortex Boilers is covered by a five-year guarantee and, when installed by a Grant G1 Installer, all other components of the boiler are guaranteed for five years from the date of installation (subject to the product being installed in accordance with the manufacturer’s instructions). Meanwhile, with the Grant VortexBlue Boilers, these are available with a ten-year guarantee when installed by a Grant G1 Installer which includes a ten-year guarantee on the heat exchanger (again, when installed in accordance with the manufacturer’s instructions).

If a Grant boiler is not installed by a Grant G1 Installer, it will be available with a two-year parts and labour guarantee which includes a five-year guarantee on the heat exchanger as well.

All Grant boilers must be registered with Grant UK and installations can be registered online via their website or G1 Portal (G1 installations only).

Grant recommends that their boilers are serviced annually by a competent engineer not only to maintain the product’s guarantee but to also help prolong the lifespan of the boiler and ensure it is working as efficiently as possible.

Grant parts and repairs

If a problem develops, contact your installer or commissioning engineer in the first instance to ensure that the fault is with the boiler, not any other heating system components. If the boiler is registered and under guarantee, you must then contact Grant UK who will arrange for the repair under the terms of its warranty. This is provided the boiler has been correctly installed and commissioned, serviced (if older than 12 months) and the fault is not due to tampering, running out of oil, freezing, or the failure of any external components not supplied by Grant UK.

Ask your installer to contact Grant, which will arrange for a qualified engineer to attend to the fault.

Grant service department 

01380 736920 

Grant contact details

Write to Grant at:

Grant Engineering (UK) Ltd.

Hopton House, Hopton Industrial Estate,



SN10 2EU

You can contact Grant by calling 01380 736 920.

Grant boiler customer service

01380 736920