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Oil Boiler Replacement Costs, Types & Warranties

If your oil boiler has broken, costing you too much to run or malfunctioning regularly it may be time to consider a replacement.

Why Install a New Oil Boiler?

  • Save money through lower energy bills
  • Safer, more reliable heating
  • Reduce carbon footprint with lower carbon emissions

A new condensing oil boiler will be far more energy efficient which should save you money on energy bills. In fact, many modern boilers can reach efficiency levels of up to 95% which means only 5% of the money you spend heating your home is wasted. When you compare this to the 60% efficiencies of many older boilers this is a potentially huge saving. And, in addition to the financial benefits and lower carbon emissions, replacing an ageing boiler with a new model could carry safety benefits too.

An oil boiler requires a tank of oil to be stored on your property which is connected to your boiler. This tank can be kept above or below ground. Oil suppliers will deliver your fuel as needed so will need easy access to the tank.

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Oil Boiler Prices

Oil boilers tend to cost between £1,200 – £2,500 but the largest models can reach in excess of £3,000. The price of a new oil boiler varies depending on which brand, size and model of boiler you choose. In addition, if you do not already have an oil tank installed you will need to either invest in one or choose an oil supplier which will rent the tank to you. Tanks are typically available in sizes between 1,000 – 3,500 litre capacities. Single skinned tanks are cheaper than double skinned.

When purchasing any new boiler the installation cost needs to considered as an addition to the price of the boiler itself. As you’d expect, the more complex the installation the higher the cost is likely to be. For example, if you need to install an oil storage tank, extra pipework or new radiators this will add to the cost. The cost of labour usually falls between £800 – £2,000 on average.

In addition, a Powerflush (£300 – £500) is often necessary before any new boiler is fitted as it clears your heating system of sludge and debris which has built up over time and prevents contamination of the new boiler.

Brand/Model Available Outputs Efficiency Grade Dimensions (mm) Price Range (Approximate)
Firebird Enviromax Combi 20 / 26 / 35 A (90.7%) 845 x 665 x 605 £1,600 – £2,200
Grant VortexBlue 21 / 26 / 36 A (90.81%) 21 & 26: 860 x 614 x 606 36: 900 x 614 x 606 £2,500 – £2,800
Worcester Bosch Greenstar Heatslave II 12/18 / 18/25 / 25/32 A (89%) 855 x 520 x 600 £2,100 – £2,500
Warmflow Utility HEE Combi 15-21 / 21-26 / 26-33 A (89.1%) 595 x 865 x 600 £1,500 – £1,900
Mistral Combi Standard 15-20 / 20-26 / 26-35 / 35-41 A (90%) 865 x 600 x 600 £1,400 – £2,800

REMEMBER…These prices are given as indicative figures only and do not include installation. The cost of installation for any boiler will vary from installer to installer so it’s important to get multiple quotes. This is the best way to compare prices, aftercare services, customer recommendations and warranties.

Choosing Your Oil Boiler

Combi, System or Regular?

The type of boiler you need – Combi, System or Regular – will largely be decided by the size of your home and the level of demand for heating and hot water.

Combi: A Combi boiler is a very popular choice for small to medium sized homes. As an all-in-one unit it does not require a hot water cylinder or feed and expansion tank which is a great space saver. It takes its water supply directly from the mains which usually delivers a strong water pressure and produces hot water on demand i.e. no waiting for the water to reheat.

System: A System boiler heats the mains water supply for your central heating but needs a hot water cylinder to produce water for your taps and showers. The advantage of a System boiler is that the hot water cylinder means a greater volume of hot water is available at one time so multiple outlets can be supplied. This is often a preferred choice for larger homes with more radiators and multiple bathrooms.

Regular: Usually found in older homes, a Regular boiler is also referred to as ‘traditional’ or ‘conventional’. The boiler is supplied with water via a feed and expansion tank in the loft which feeds the boiler through gravity and a hot water cylinder is required to enable it heat water for taps and showers. A Regular boiler is a possible choice for older homes with pipework that won’t cope with mains pressure.

Internal or External?

Oil boilers can be sited internally or externally. If space in your home is limited you may find that an external version is preferable or you can often opt for a boiler house model which can be sited in a garage or outhouse.

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Oil Boiler Brands


Grant is a Wiltshire based company which produces a range of condensing oil fired boilers alongside renewable heating products such as biomass boilers, solar thermal technology and air source heat pumps. The Grant oil boiler range includes Combi, System and Regular boilers for both internal and external installation.

Worcester Bosch

Worcester Bosch are a leading heating brand offering a range of both condensing gas and oil fired boilers for homes of every size. Originally a UK brand called simply Worcester, they were acquired by the global Bosch group in 1992. They produce Combi, System and Regular oil boilers in a range of floor standing and wall mounted models.


Firebird logoFirebird is an Irish company specialising in condensing oil fired Combi, System and Regular boilers. The Firebird range includes boilers for internal and external installation as well as models designed for utility or boiler house siting.


Mistral logoMistral, a 40 year old brand, offers both condensing and non-condensing oil boilers for almost every type of installation including commercial purposes. Their Combi, System and Regular boilers are available for internal or external installation.


Warmflow has been producing oil boilers for over 45 years and today offers Combi, System and Regular options for most sizes of home. The range is suitable for internal, external, utility room or boiler house installations.

Oil Boiler Warranty

The length of warranty included with your oil boiler will vary depending on the manufacturer you choose. Generally, oil boiler warranties will fall between 2-7 years in length but some manufacturers offer up to 10 years with certain models. Warranties should be registered within 30 days of installation and, to ensure they remain valid, you will need to get the boiler professionally serviced annually.

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What is the OFTEC Register?

The Oil Firing Technical Association or OFTEC is the official organisation which recognises the competence of boiler engineers installing and repairing oil appliances. While engineers are legally required to be Gas Safe registered if working with gas fired appliances, it is not a requirement that an engineer is OFTEC registered in order to work on an oil fired appliance.

However, if the boiler has been installed by an engineer who is not OFTEC registered it will need to be checked by a third party to ensure it satisfies building regulations. By ensuring your engineer is recognised by OFTEC you are employing someone who is able to complete the work safely and competently and declare that it is compliant with building regulations. In addition to ensuring a professional and safe installation this should also save time and inconvenience.

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