Oil Tank Sizing Calculator — What Size Oil Tank Do I Need?

A typical UK home with oil-fired central heating uses between 1,500 and 2,500 litres of kerosene per year. A well-insulated smaller property might use as little as 1,000 litres, while a larger or poorly insulated house could use 3,000–4,000 litres. The average is around 1,800–2,200 litres per year. Actual consumption depends heavily on property size, insulation levels, local climate, and thermostat settings. Use our Boiler Size Calculator to check your heating system is correctly sized.

Following an OFTEC oil storage risk assessment (form TI/133D), a bunded tank is required if any of these apply: the tank is within 10 metres of a watercourse (a river, stream, ditch or surface-water drain); within 50 metres of a borehole, spring or well; in a position where a spill could run into open ground or a drain; or the tank capacity exceeds 2,500 litres. These triggers come from the Control of Pollution (Oil Storage) Regulations and Building Regulations Approved Document J (England; equivalent standards apply in Scotland and Wales). OFTEC recommends bunded tanks for all new installations regardless of location, and a bund must hold 110% of the tank's capacity to contain any spillage. Many insurers now require bunded tanks as standard.

Common UK domestic oil tank sizes are: 1,100 litres (standard single-skin), 1,225 litres (slim-line), 1,400 litres, 1,800 litres, 2,500 litres, and 3,500 litres. The most popular domestic sizes are 1,100L and 1,225L for smaller properties, and 2,500L for larger homes or those wanting fewer deliveries. Tanks are available in plastic (polyethylene) or steel, with plastic being the most common for domestic use.

Under OFTEC guidance and Building Regulations Approved Document J, a domestic oil tank must be at least 1.8 metres from a non-fire-rated building or structure (including the non-fire-rated eaves of a building), from any opening such as a door, window or flue terminal, and from any liquid-fuel-fired appliance flue terminal. It must also be at least 760mm from a non-fire-rated boundary such as a wooden fence, and at least 600mm from screening that does not form part of the boundary, such as trellis or foliage. Where these distances cannot be met, a fire-protection barrier with at least 30 minutes' fire resistance (extending 300mm above and beyond the tank) can be used instead. The tank should sit on a non-combustible, level base (typically concrete or paving slabs) that extends at least 300mm beyond the tank on all sides.

Most domestic oil users order every 6-12 weeks during the heating season, with less frequent deliveries in summer. Ordering in larger quantities (500+ litres) usually gets a better per-litre price. Joining an oil buying syndicate or co-operative can also reduce costs by 2-5p per litre. Monitor your tank level regularly — running out of oil can introduce air into the system, requiring a boiler service to restart. Many suppliers offer automatic top-up services based on weather and estimated usage.