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Buying an oil boiler

By Matthew Knight

Find out which households are most suited to an oil boiler, how oil boilers work and typical oil boiler prices. Once you have all the information you need, why not look at our oil boiler reviews.

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In this guide you will find;

For the estimated four million households not connected to the UK's gas network, an oil-powered central heating system with an oil boiler is a key alternative for heating a home.

There are fewer oil boilers to choose from, but the market still offers a good degree of choice when upgrading your oil heating system. We've reviewed and rated more than 80 models on measures including reliability. 

Use our oil boiler reviews to filter your results by fuel type, so you can browse the full range of oil boilers we've rated.

How oil boilers work 

An oil central heating system works in a similar way to a gas-powered system. But instead of using a gas boiler, it uses an oil-fired boiler to heat water. This provides the central heating via radiators and hot water through the taps in your home. 

The main difference between the two systems is that you'll need to have your oil supply delivered and stored in a tank. You can read more about heating oil tanks, prices and ordering in our guide to heating oil

We've also found that it’s common for the hot water temperature to decline in oil systems, as more water is used. For more information on the pros and cons of an oil central heating system, see our home heating systems guide.

Oil combi boilers 

You'll find both heat-only and combi oil boilers on the market. Most oil-fired combi boilers have an internal hot water store to supply domestic hot water, rather than the instantaneous heating more common in gas boilers.

You can buy oil boilers from brands such as; 

  • Grant
  • Firebird
  • Mistral
  • Warmflow
  • Worcester Bosch

But before you buy, make sure you pick an oil boiler from one of the most reliable brands by reading our oil combi boiler reviews

How much do oil boilers cost? 

Oil boilers vary in cost depending on the type (combi or heat-only) and size, measured in kW of the boiler. You can use the table below to give you a guide to what you might expect to pay. 

Oil boiler costs
Type of boiler Price range
Large combi £2,300 - £3,000
Small combi £2,000 - £2,500
Large heat-only £1,500 - £3,800
Small heat-only 1,200 - £2,600

The cost of the boiler will only make up a slice of the cost of the installation. You should expect to pay between £3,000 and £5,000 for an oil boiler installation, depending on the amount of work that's required, whether the location of the boiler is moving or not, and the size of your home. The bigger your home, the longer it will take to balance and clean the heating system, so the costs will be a bit higher than with a smaller home. 

How much will it cost to heat your home with oil? 

The average cost of oil heating for a three-bedroom house is around £1,355. This compares to between £770 and £950 for mains gas, depending on the efficiency of your boiler, and £1,300 for liquid petroleum gas (LPG), the other fuel of choice in the countryside.

Oil is a more efficient fuel than gas, so you'll get a good return on every unit of energy. But, like gas, the price of oil can fluctuate so sometimes it will be more cost effective. 

To conform with building regulations, since 1 April 2007 oil-fired boilers must have a Sedbuk efficiency of 86% or more (unless an exception is allowed). Typically, a new condensing oil-fired boiler will have an efficiency of 92% to 93%, compared with 60% to 70% for older systems.

How do I maintain an oil boiler? 

You should choose a professional registered with the Oil Firing Technical Association (Oftec) to install an oil boiler and heating system. 

Which? Trusted Traders can help you find recommended boiler servicing engineers in your area – and it's advisable to have your oil boiler serviced each year.

Want to know which oil boiler brands are the most reliable? We reveal the best oil boiler brands.


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