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Oil Central Heating Boilers

There are well over four million homes in the UK, which are not connected to the mains gas supply. The majority of these are in rural areas, and while it is worth investigating the cost of laying a connection to the mains supply, in many cases it will be too expensive or not practical.

Oil must be stored in a tank which supplies the heating boiler.

Central heating oil being derlivered to the storage tank

Alternative fuels include LPG tank gas, electricity, wood chips or pellets, and oil.

Although generally considered more expensive and less friendly to the environment, new highly efficient condensing boilers mean that oil is an acceptable alternative where gas is not available.


How do oil boilers work?

Oil must be stored in a tank on the property, from which it is pumped to the boiler and burned to provide heat. The heat is transferred to the water in the central heating circuit via a heat exchanger.

A network of pipes carries the hot water around the house to provide heat to the radiators, and can also run through a coil in the hot water storage cylinder to heat your water.

Since 2007 building regulations have required that any boiler fitted with an oil system must be a condensing boiler, and many of the oil boilers on the market are up to 97% efficient.

Combination oil boilers are also available to power central heating, and much like a gas combi boiler, they heat water on demand rather than heating it in a storage cylinder.

Combination boilers may be suitable in smaller properties, although they are not always as quick at supplying the hot water to the outlets as gas boilers, so may not be practical in a larger house.

Oil boilers also require a flue, and boilers are available with balanced flues or open flues. The air for combustion is drawn from the room where the boiler is sited for an open flue, while balanced flues take the air through a pipe, which runs alongside the extraction flue.

Building regulations do allow either style to be fitted in a garage, but it is worth checking any conditions on the location of the boiler, and the external oil storage tank.

The majority of oil boilers use 28sec heating oil (kerosene); it burns very cleanly, and can also be used in kitchen range cookers and AGA’s.


Why use oil?

Oil central heating boilers are only generally used when there is not a mains gas supply. It is more expensive than gas, and is one of the highest carbon-producing fuels. A condensing oil boiler could produce up to 5,000 tonnes of carbon dioxide per year, and has a higher figure for carbon produced per kWh than most other fuel types.

Oil is considered to be one of the most efficient fuels, in that it produces more heat per unit of energy, but the price of the oil still means it is more expensive. Oil also needs to be delivered, and as well as the cost of delivery, you also need to remember to order regularly to make sure you don’t run out.

This can sometimes be monitored by your supplier, so if you use oil, try to arrange an ongoing relationship with a supplier.


Which boiler?

The most efficient boiler is the key choice

It is essential to choose the most efficient boiler possible.

Figures released by DEFRA, give carbon content per kWh for different fuel types to show the different impact each has on the environment. Mains gas produces 0.184kg of CO2 per kWh, while heating oil produces 0.245kg CO2 per kWh.

This indicates how much less friendly oil is to the environment, so it is important to fit the most efficient boiler possible.

There are now several ‘A’ rated oil boilers available on the market and you can easily check the efficiency rating of any boiler at the SEDBUK website:


A condensing boiler is probably the most efficient type of boiler to use with an oil-fired system. The most modern oil boilers have efficiency ratings of up to 97%, which helps to reduce running costs and to lessen the impact on the environment.

Combination oil boilers may be better in very small properties, but are unlikely to meet the demand for domestic hot water in a larger house.

Most condensing oil boilers are free standing, although there are some models available which are wall-mounted. Consider where the boiler will be located, and if there is enough room to accommodate it.

You should also think about where the external oil storage tank will be sited; they can be something of an eye sore in the garden, and you might prefer to install an underground tank.


Installation, running costs & central heating oil prices

Heating oil prices are generally higher than gas prices, and this pushes up the running costs. Although heating bills will depend on the size of the property, the efficiency of the system, and the way the heating is used, the rough cost of running an oil-fired system would be £1100 – £1400 per year.

This is based on a typical three bedroom house, which uses 16,000 kWh of heat output annually for heating and hot water. An equivalent property would cost £700 – £1000 to heat with a gas system and could cost well over £2,000 with electricity.

The installation of a full oil central heating system, with radiators, pipe work, and controls would cost approximately £3,500 – £4,500, while the installation of an external storage tank would be in the region of £2,800.

The vast majority of homes in the UK are connected to the mains gas supply, and this is by far the most common fuel used for central heating. For the four million or so homes, which are not connected to mains gas, oil is one of the alternative fuel types that can be stored on-site and used for heating.

Newer, and more efficient condensing boilers have reduced the amount of carbon produced by the burning of oil, and although still much less friendly to the environment than gas, the difference is markedly less than it was with older boilers.

The cost of heating with an oil system will be more than with gas, but much less than with electricity; this makes oil a viable choice for houses without a gas supply.

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