Oil Combi Boilers in the UK: Prices, Pros & Cons

Oil combi boilers are heating systems that use oil as a fuel to provide both hot water and central heating. In the UK, over 4.4 million households are estimated as off-grid, making accessibility to alternate heating systems such as oil fired boilers increasingly important. 

These versatile heating systems are highly energy-efficient (94.5%) and compact, suitable for small (1-2 bedroom) to medium houses (3-4 bedrooms). If you are looking for an energy-efficient heating system that is also durable (15+ years), oil combi boilers might be the answer for you. 

If you're looking for the most efficient boilers for your home but do not have hours of spare time to vet local installers, we can do the heavy lifting for you. Greenmatch can help you get tailored new boiler costs from trustworthy local installers quickly. 

Simply click on the button below and fill out the 30-second form to get up to 3 free and non-obligatory quotes.

Oil fired combi boilers are heating systems that supply hot water and provide central heating for a house. Combination (or combi) boilers can come in e a variety of fuel options, including natural gas, LPG (liquified petroleum gas), electricity, wood pellets (biomass) and oil. 

While gas boilers and electric combi boilers are amongst the common types of boilers in the UK, oil fired boilers are typically installed in homes without access to the gas grid. The main distinction between these boilers is their fuel storage. An oil fired boiler requires a constant oil supply, delivered and stored in a tank, unlike gas boilers which receive their fuel from the gas mains. 

Oil combi boilers can be extremely energy efficient as oil boilers use all of the thermal energy produced and condensing combi technology means heat from exhaust gases is reused to provide heating. This ensures more heating for every unit of oil used, making modern condensing oil boilers cost-effective. 

They are also one of the best boilers for households off the gas grid. They are durable, as they last up to 15 years or longer with proper maintenance. Additionally, the recent government plans to phase out oil fired boilers have been pushed back, so you can still get them installed. 

The oil combi boiler has several components, including the external oil tank, combustion chamber, heat exchanger, and flue. The following are the steps involved in the functioning of the boiler: 

The boiler unit can be either placed inside, called an internal boiler or outside, called an external boiler. There are also two types of oil tanks— Above-Ground Storage Tanks and Bunded Tanks. Above-Ground Storage Tanks are commonly used for domestic heating oil storage. They can be made of steel or plastic and are placed on a stable surface, often on a concrete base.

Bunded Tanks are recommended for larger storage capacities (over 2,500 litres) and provide an additional layer of protection by having a secondary containment system to prevent oil spills from reaching the environment

The average costs of oil combi boilers fall within £1,300 - £4,000, without the installation costs. Read on to find out about oil combi boiler costs according to energy output and suitability for different house sizes. 

*These price ranges are estimates based on our market research. 

You can calculate the right boiler sizes by understanding the energy requirements of your house. On average, every radiator would require 1.5 kW. You should also account for potential heat loss by considering your home’s insulation levels and window types and sizes. 

Therefore, for a small house of 1-2 bedrooms, 1 bathroom, and about 10 radiators, you would need a 20kW-26kW oil combi boiler. An oil combi boiler unit in this range would set you back by £1,800-£3,800. You will need a 28-34kW boiler for a medium house with 2-3 bedrooms, 2-3 bathrooms, and 15 radiators. The cost of such an oil fired combi boiler would be around £1,800-£4,000. 

Oil combi boilers are not the best boiler for large houses as they are primarily designed for small spaces. But there are boiler models with higher capacity available in the market such as the Grant Vortex Pro (36kW). We have calculated that for a large house with 4-5 bedrooms, 3+ bathrooms, and 20 radiators, 35-43kW boilers would be needed. This would cost around £1,900-£4,600 (excluding installation). 

It is important to take into consideration the extra costs involved in installing oil combi boilers. Apart from the cost of the boiler unit, there are installation costs. The estimated installation price for oil combi boilers is £1,000 - £2,000 . 

*These price ranges are estimates based on our research. 

Oil fired combi boiler prices inclusive of installation costs would be more. Thus, the total costs for a 20-26kW oil combi boiler would be £2,800-£5,800. 28-34kW boilers would cost around £2,800-£6,000 and 35-70kW boilers would cost £2,900-£6,600. 

The installation cost depends on the complexity of the job. A new boiler installation typically takes about one day to complete. At the same time, if a boiler replacement is done, some extra pipework might be required, which might take longer. 

The installation process includes the following steps:

The following section outlines the pros and cons of oil combi boilers. 

Pros 

Cons 

Oil combi boilers can be a good option for your household heating needs if you do not have access to the gas grid. Oil combi boilers are fairly durable as they last for 15+ years and have high energy efficiency (up to 94.5%). But, you should read about the best boiler brands and the boiler types before finalising on a boiler unit. 

If you have decided on a new boiler for your house, it is recommended to compare quotes from different installers to ensure you get the best deal. With Greenmatch, you do not have to spend hours looking for the best combi boilers, system boilers, and reliable local installers. 

You can simply fill out our 30-second form to receive up to 3 boiler quotes from suppliers near you, to help you compare the best deals. This service is completely free and non-binding.