Oil Fired Combi Boilers

What is an Oil Fired Combi Boiler?

Most people think of gas when it comes to home heating, but millions of UK properties are off-grid. For these homes, oil remains one of the most common alternatives for central heating and hot water.

Oil fired combi boilers work in a similar way to gas boilers, but instead of burning natural gas, they use heating oil (usually kerosene). Depending on the model, some oil “combi” systems include a small hot water store or cylinder rather than producing unlimited hot water on demand, so performance can vary between brands and designs.

The most noticeable difference is the need for an external oil storage tank, usually located in the garden. This tank feeds the boiler via pipework and filtration, providing a steady supply of fuel whenever heating or hot water is required.

Eager to learn more about how a Combi Boiler works? Then read our What is a Combi Boiler? article to find out more.

Oil Fired Combi Boiler Prices

Oil fired combi boiler prices vary depending on the brand, efficiency rating, output (kW), and whether the unit includes a built-in hot water store. As a general guide, most supply-only oil combi boilers fall within the range of £1,800 to £5,500, excluding installation and the oil storage tank.

Boiler size is measured in kilowatts (kW). When choosing a boiler, you should consider the size of your home, the number of radiators, insulation levels, and how many bathrooms or showers are in use. Larger homes with higher hot water demand typically require a higher output boiler.

Typical guideline ranges:

Please note: These figures are a guideline only. Always speak to a qualified installer to determine the correct boiler size for your home.

Looking for a new Oil Combi Boiler? Check our The Best Oil Combi Boilers Guide for expert recommendations.

Oil Fired Combi Boiler Installation Prices

Installation costs for oil fired combi boilers are usually higher than gas installations due to the additional work involved. This can include oil line installation, tank siting, safety clearances, flue routing, and commissioning.

As a rough guideline, installation costs often range from £1,800 to £4,500+, depending on:

• Whether the boiler is a like-for-like replacement
• If the boiler or flue needs relocating
• Upgrades to heating controls
• The condition and position of the oil tank
• Any groundwork or safety requirements

Homeowners also need to consider the oil storage tank itself. Common domestic tanks typically start at around 1,000 litres. Prices vary based on tank type (single-skin or bunded), access, and whether a new base is required. Some suppliers may offer tank rental options.

Need advice on your new Oil Fired Combi Boiler? Complete our Quick Quote Form and we’ll arrange for someone to contact you to discuss your requirements and budget.

How Much Does Oil Heating Cost Per Year?

The cost of oil heating can vary significantly from year to year because heating oil prices fluctuate and are not price-capped in the same way as mains gas or electricity.

Your annual heating bill depends on several factors, including:

• Property size and insulation
• Boiler efficiency
• Heating usage habits
• Outdoor temperatures
• Oil prices at the time of purchase

A simple way to estimate annual costs is:

(Litres of oil used per year) × (Current price per litre)

If you’re unsure how much oil you use, check your past delivery invoices or ask your supplier for a usage summary. Improving insulation, servicing your boiler, and upgrading heating controls can all help reduce fuel consumption.

Many homeowners prefer oil because it offers strong heating performance and the option to buy fuel in bulk when prices are lower. However, budgeting is important, as prices can change quickly during colder months.

Oil Fired Combi Boiler Maintenance and Efficiency

Oil fired combi boilers require regular servicing to ensure safe, efficient operation. It’s recommended that you always use an engineer registered with OFTEC (Oil Firing Technical Association), as they are qualified to work on oil-fired appliances.

Modern oil boilers are typically 90–95% efficient, especially condensing models. Older non-condensing systems can be far less efficient, often operating at 60–85%. Upgrading to a newer boiler can significantly reduce fuel usage and improve heating performance.

OFTEC Register

Before any oil heating work is carried out, it’s important to check that your engineer is OFTEC registered. The OFTEC register ensures installers meet safety and competency standards for oil-fired systems.

OFTEC engineers can certify installations in line with building regulations, helping you avoid future safety issues, compliance problems, and unexpected costs.

The future of Oil Heating

The UK’s long-term energy strategy focuses on reducing carbon emissions and increasing the use of low-carbon heating technologies, particularly in new-build homes.

Existing oil-heated homes can continue using their current systems, and there is ongoing development in alternative liquid fuels and renewable heating options that could support off-grid properties in the future.

Industry bodies have suggested that lower-carbon liquid fuels, such as bio-fuel blends, could play a role in reducing emissions for oil-heated homes without the need for major system changes.

Alternatives to Oil Fired Combi Boilers

Renewable heating systems such as heat pumps and solar thermal panels are increasingly popular alternatives. These systems can reduce carbon emissions and may be supported by government incentive schemes.

Each property is different, so the best option depends on your home’s insulation, space, budget, and location.

Read our Boiler Plus Article to learn more about the government’s ‘Clean Growth Strategy’.