Oil boiler installation and off-grid heating

Types of oil boiler

Oil boilers come in the same basic types as gas: combi boilers, system boilers and regular boilers. The right one depends on how much hot water you use and how your heating system is set up now. A new oil boiler will be a condensing model, which gets more heat out of every litre than the old non-condensing boilers many farmhouses still run.

• Oil combi boiler: combi oil boilers give heating and hot water on demand with no cylinder. Good for smaller homes with one bathroom and decent mains pressure.
• Oil system boiler: heats a hot water cylinder for homes with two or more bathrooms in use at once.
• Regular (heat only) boiler: works with a cold water tank in the loft and a cylinder. Often the simplest swap in an older house.
• External oil boiler: sits outside in a weatherproof casing, freeing up space indoors and keeping the flue outside the house.

What an oil boiler replacement involves

Replacing your oil boiler starts with a survey. We check the old boiler, the flue route, the oil supply line, the fire valve and the oil storage tank, because a new boiler is only as good as the fuel reaching it.

On the day, the old boiler is drained down and removed, and the new oil boiler, flue and controls go in and are connected to your central heating system. Where the oil line or filter is tired, we replace them at the same time. The boiler is then commissioned and tested with a flue gas analyser.

Oil boiler installation is notifiable under Building Regulations. Our OFTEC registered technicians self-certify the work, so you get the paperwork without arranging a separate building control inspection.

Oil storage tank rules

If the oil storage tank does not meet current rules, we plan a new oil tank as part of the job. The main points from Approved Document J and gov.uk:

• Tanks of 3,501 litres or more need secondary containment, and a bund must hold 110% of the tank
• Smaller domestic tanks need a bund too where there is a significant pollution risk, for example a tank over 2,500 litres or within 10m of a watercourse
• A tank should be at least 1.8m from the building and 760mm from a boundary, unless fire-resisting walls or screens are added
• It needs a solid base, such as concrete or paving slabs at least 42mm thick, extending 300mm beyond the tank all round

Oil boiler costs and running costs

The cost to install an oil boiler depends on the model, where it goes, the flue and whether the tank or oil line needs work. A like-for-like swap that keeps a sound tank costs less than a move to a new position with a new oil tank. We price each job after a free survey, with one fixed figure covering the boiler, any tank work and commissioning.

Oil boiler running costs follow the price of oil, which moves with the market, so it pays to keep the boiler serviced and burning efficiently. A yearly oil boiler service also keeps the manufacturer warranty valid.

Alternatives to oil

If you are replacing an oil boiler anyway, it is worth weighing up the alternatives to oil. An air source heat pump can attract £9,000 through the Boiler Upgrade Scheme until March 2027 if your home has no mains gas, and it removes fuel deliveries altogether.

LPG suits homes with no room for an oil tank, and our LPG vs oil guide compares the two. For some big, draughty farmhouses a new oil boiler is still the sensible choice for now, and we will say so.