Guide to Oil Boiler Costs, Installation & Savings

The average price of a new oil boiler is £2,613 depending on the boiler size (kW).

With installation included, the typical oil boiler replacement cost is £5,963.

In this guide, the WhatPrice team is here to provide a full cost breakdown of the average oil boiler replacement in the UK.

As a homeowner, property developer or tenant, we’ve included everything you need to make an informed purchase decision.

Introduction to oil boilers

If you’re looking at buying an oil boiler, there is a good chance you are living on a rural land, or a similar property type which isn’t connected to the gas mains.

You could be looking to replace an existing oil boiler having lived in your property for a long time.

Or, you may have only just moved into your off-grid property and are used to having a wider choice of boiler types to choose from.

On the whole, it is less likely to see oil boilers installed in urban locations, especially where gas mains connection is possible. Likewise, from 2025 onwards the government has banned oil boilers from being installed in new build homes.

The current timeline to phase oil boilers out for good is 2035. However, as things stand this date remains a proposal and has not been made official government legislation. Therefore, if you are looking to replace an oil boiler today, rest assured oil boilers are still widely available to purchase including from lots of well-known brands.

What is an oil boiler?

An oil boiler is a combi, system or regular boiler which uses oil (usually kerosene) as its main fuel source.

Oil boilers require on-site storage as the oil is delivered in large quantities. Similar to gas boilers, oil boilers also require an external flue. However, a key difference is that oil boilers can be installed inside (internal boilers) or outside (external boilers).

If you opt for an external oil boiler, this will work to free up space and can also prevent carbon monoxide or oil leaks from happening inside your home. Though, it is rare for modern oil boilers which are regularly serviced to experience such issues.

In summary, the main thing you need to know about oil boilers is that they are geared towards off-grid properties.

How do oil boilers work?

As we’ve just established, an oil boiler runs on oil. Unlike gas which is piped directly to your home, you will need to arrange for your oil to be delivered to your property. The oil is then stored in a large tank so that the boiler can draw the oil whenever hot water or heating is needed.

Once the oil reaches the inner components of the boiler, it is ignited in a burner which creates the necessary heat. The heat exchanger then warms the water within a sealed system, making it ready for distribution throughout radiators and hot water taps.

Who needs an oil boiler? (Best use cases)

Oil boilers have long offered a solution for off-grid homes which do not have a mains gas supply to be able to get a gas-fired boiler.

While off-grid homes can also be converted to greener fuel sources, this isn’t always feasible due to practical or financial reasons. In rare cases, historic properties may not be able to get listed consent to be able to make the necessary changes to convert the property’s central heating system.

Heat pumps may also be incompatible with period properties which lack the required insulation.

Therefore, an oil boiler may remain the only suitable choice if you require a powerful and reliable way of heating your home and hot water when dealing with any of the above restrictions.

Oil boiler costs in 2025

Boiler brand	Boiler make	Boiler type	Boiler size	Average new oil boiler cost (excluding installation)
Firebird	Envirogreen Popular C100 External	Regular	100kW	£5,332.79
Firebird	Envirogreen Kitchen C35 Internal	Regular	35kW	£2,407.19
Firebird	Envirogreen Heatpac External	Regular	26kW	£2,317.85
Firebird	Envirogreen Slimline Heatpac	Regular	26kW	£2,174.39
Firebird	Envirogreen Popular Boilerhouse	Regular	18kW	£1,393.19
Firebird	Envirogreen Kitchen	Regular	20kW	£1,752.34
Firebird	Envirogreen	Combi	26kW	£2,627.99
Firebird	Envirogreen Slimline	Combi	20kW	£2,662.79
Firebird	Envirogreen Internal	System	26kW	£2,170.79
Firebird	Envirogreen Systempac External	System	26kW	£2,632.79
Grant	Vortex Pro External	Combi	26kW	£3,529.19
Grant	Vortex Pro External	Combi	21kW	£3,299.99
Grant	Vortex Eco External	System	35kW	£3,119.99
Grant	Vortex Eco External	System	21kW	£2,379.59
Grant	Vortex Eco Internal Wall Hung	Regular	16kW	£1,619.99
Grant	Vortex Eco External	Regular	21kW	£2,025.59
Navien	Internal LCB	System	28kW	£1,910.39
Navien	External LCB	System	21kW	£1,953.59
Navien	Internal LCB	Regular	21kW	£1,684.79
Navien	Internal LCB	Regular	28kW	£1,747.19
Navien	Internal LCB	Combi	28kW	£2,639.99
Navien	Internal LCB	Combi	21kW	£2,601.05
Warmflow	Agentis Internal	Combi	26kW	£3,209.99
Warmflow	Agentis External	Combi	21kW	£3,249.59
Warmflow	Agentis Internal	Combi	33kW	£3,520.79
Warmflow	Agentis Internal	Regular	21kW	£1,769.99
Warmflow	Agentis Internal	Regular	44kW	£2,917.19
Warmflow	Agentis Internal	System	21kW	£2,063.99
Warmflow	Agentis Internal	System	33kW	£2,479.19
Worcester Bosch	Greenstar Heatslave II	Combi	32kW	£3,739.19
Worcester Bosch	Greenstar Danesmoor External	System	25kW	£3,232.79
Worcester Bosch	Greenstar Danesmoor	System	25kW	£2,518.79
Worcester Bosch	Greenstar Heatslave II	Combi	18kW	£3,317.99
Worcester Bosch	Greenstar Danesmoor Utility	Regular	18 kW	£2,051.99
Worcester Bosch	Greenstar Utility	Regular	70 kW	£3,415.19

How much does a new oil boiler cost?

The typical oil boiler cost ranges between £1,393.19 to £5,332.79. This gives an average cost of
£2,613.43.

We looked at the most popular oil boiler brands and boiler types for sale to create our average costs.

There is a lot to unpack when understanding the cost of a new oil boiler. That’s because the price will depend on the:

• Boiler type (i.e. combi, regular or system)
• Boiler size (kW)
• Boiler manufacturer
• Boiler make
• Installation location (oil boilers can be installed inside or outside your property)

On the whole, we found Navien boilers to offer the cheapest option for oil boilers. The priciest oil boilers are those made by Firebird, but they have higher costs due to the extremely innovative technology these boilers possess.

Oil boiler costs by type (combi, system, conventional)

Oil boiler type	Average price range
Combi	£1,500 – £4,500
System	£1,300 – £3,200
Regular (conventional)	£1,000 – £3,000

As a homeowner, you may be surprised to know that unlike gas combi boilers, oil combi boilers are not the cheapest option when it comes to the lowest type of oil boiler replacement cost. While it’s possible to find cheaper entry-level models, you can pay up to £4,500 for the cost of a new oil combi boiler.

Instead, budget-conscious homeowners should look for a system or regular boiler. Our research found regular (conventional) boilers had the cheapest average purchase costs of between £1,000 and £3,000.

Price comparison: Oil vs. gas vs. electric boilers

Boiler type	Average boiler cost
Oil	£2,500 – £5,000
Gas	£2,000 – £3,500
Electric	£1,500 – £3,000

With an average unit cost of between £2,500 and £5,000, oil boilers have a more expensive upfront cost compared with gas and electric boilers.

The reason why oil boilers cost more is due to being less common. It’s thought around 85% of UK homes have gas boilers, meaning fewer manufacturers make oil boilers. Likewise, there are fewer oil boiler installers available compared with gas boilers or even modern heat pumps.

Hidden costs to consider

All boiler installations can have hidden costs depending on the specifics of your property.

With an oil boiler installation you will also need an oil tank. If you don’t have an oil tank, or if your existing oil tank is at the end of its life, this can add £1,000 to £2,000 to the total cost.

Unless you have an existing oil tank, you may also require a ‘first fill’ of the tank. Based on the current oil prices, adding 500L of oil can cost between £300 and £400.

If upgrading to a modern oil combi, system or regular boiler, you may also wish to add smart controls to your heating system. This can potentially add a few hundred pounds to the job.

There could be additional costs involved in an oil boiler installation if any part of your system doesn’t meet building regulations, or if your engineer spots signs of damage or corrosion. Likewise, if you need to relocate your boiler, this will cost more compared with a like-for-like swap.

Oil boiler installation costs & process

The process of installing an oil boiler starts with an engineer assessing your current setup to decide what the job will involve. This could range from a like-for-like swap, a boiler conversion (i.e. regular to combi boiler) or the complete design of a heating system to be installed from scratch.

Plans will be drawn up which will cover everything the boiler installation needs including based on any building regulations.

The typical oil boiler installation involves the following steps:

• Removal of existing boiler
• New boiler fitted in the chosen location
• Connections made between the fuel tank, water in/out, flue and power supply
• Pipework upgrade (if relocating the boiler or due to corrosion of existing pipes)
• Power flush of the system
• Removal of any incompatible components
• Testing of the burner, fuel pressure, thermostat, radiator performance and combustion efficiency
• Certification issued
• User handover

If installing an oil boiler from scratch, all of the necessary pipework and the tank will need to be added. This will take longer and will be more expensive than the standard like-for-like swap we’ve outlined above.

How much does it cost to install an oil boiler?

Based on our research, we found a new oil boiler costs between £1,200 and £3,500 to install. On average, this amounts to £2,350.

Something to know about the cost of installing an oil boiler is that if your engineer also sources the boiler for you, they will likely get it at trade prices. When combined as a packaged price, this can potentially save you money.

Factors that affect installation costs

Item	Typical price range
New oil boiler	£1,400 – £5,300
Installation	£1,200 – £3,500
Oil tank (if applicable)	£1,000 – £2,000
Extras (if applicable)	£300 – £800

Boiler installations requiring a like-for-like swap of the boiler unit will be easier and ultimately far cheaper overall.

Where things get more expensive is when other parts of your system require upgrading or re-routing. For an oil boiler installation, such factors can include replacing the oil tank, switching the boiler type or moving the boiler to a new location (i.e. internal to external boiler).

If your existing radiators or pipework are older, they may require an upgrade so that they are compatible with a new oil boiler, not to mention more efficient.

Modern boilers also include the installation of smart controls such as Hive or Nest. Smart control upgrades cost £300 on average.

A good way to tell if your oil boiler installation will cost more than the average amount is based on how long ago the system was installed, plus how often it has been serviced and maintained.

For instance, if you are looking to renovate a rundown property which has an oil system installed, it may work out more cost-effective to switch to a renewable fuel source instead.

How Long Does Installation Take?

Oil boiler installations can take 1-3 days to install in most cases. Installing an oil boiler for the first time can take longer, as can complex installations.

When collecting quotes from your engineer, they should also be able to tell you how long they think the job will take. Only when an engineer has assessed your property compared with your new boiler requirements can they give a tailored timeframe.

Can you install an oil boiler yourself?

No. Even though oil boilers are not subject to the same regulations as gas boilers, oil is still a fossil fuel which means the correct air-to-fuel ratios must be achieved. Attempting a DIY boiler installation can pose serious safety issues such as fires or carbon monoxide leaks.

Therefore, to avoid problems with your home insurance and also the boiler warranty, your oil boiler should only be installed by an OFTEC (Oil-Fired Technical Association) technician.

Furthermore, oil boilers also require an electrical connection to power the boiler which must be handled by a qualified professional (i.e. an electrician on the NICEIC register).

Running costs & efficiency

Understanding how much an oil boiler costs to run is important, since the running costs will directly impact your energy bills.

How much does it cost to run an oil boiler?

Price per litre	Average household yearly usage (1,900 litres)
57p	£1,083
82p	£1,558
£1.09	£2,071

In recent years, oil has been subject to volatile price fluctuations. That’s why we recommend checking today’s oil prices to get an idea of what your new oil boiler will cost to run.

Based on the prices of oil in recent years, the average UK home has spent between £1,083 and £2,071 per year on oil.

Oil boilers also require electricity to run. Thankfully the amount of electricity consumed by an oil heating system is quite modest. That said, switching to solar can reduce the cost of your oil boiler costs, plus your wider electricity costs as a whole.

Oil consumption & efficiency ratings explained

Most oil boilers in the UK use kerosene as the fuel source. The average household usage falls between 1,000 and 2,000 litres of kerosene oil per year.

Oil boilers in the UK are rated using SEDBUK (Seasonal Efficiency of Domestic Boilers in the UK) scale. To receive an SEDBUK A rating, the boiler must demonstrate over 90% efficiency.

ErP (Energy-related Products Directive) is another efficiency rating which can be applied to oil boilers. ErP runs on a scale of A+ to G.

Tips to reduce your oil heating bills

Keep an eye on oil prices – Oil prices fluctuate often throughout the year. Ordering your oil when prices fall can save you money.

Bulk buy your oil – When prices are lower, it may make sense to bulk buy.

Choose premium oil – Premium grade oil is treated with special additives which makes the oil more efficient.

Insulate your home – All properties cost more to heat when they are poorly insulated. Getting an energy survey done can outline the most wasteful areas of your property.

Control the thermostat – Avoiding heating your home excessively can ensure thermal comfort without burning more oil than is necessary.

Replace your boiler when it’s time – If your current boiler is old and inefficient, paying for the average oil boiler replacement cost now could actually save you money in the long run.

Government grants & schemes for oil boilers

Struggling to afford the cost of a new oil boiler? You may qualify for financial help from the government.

Are there oil boiler grants available in 2025?

The government is aiming to phase out oil boilers by 2035, so for the most part any financial help is currently being offered towards the cost of switching to a renewable energy source instead.

The schemes which are currently active include:

Boiler Upgrade Scheme (BUS): Provides up to £7,500 to ‘decarbonise’ your home including removing sources of fossil fuels such as an oil boiler. The BUS scheme is open to households in England and Wales. Your home must meet certain energy efficiency standards to qualify.

ECO4: A government scheme aimed to help low income households avoid fuel poverty. ECO4 can be used to pay for a new oil boiler. You must be in receipt of certain benefits and your property must have an energy performance rating of D-G to qualify.

Warm Homes Plan: This is the latest scheme introduced by the newly-elected Labour government in March 2025. It aims to cut household bills by £500 a year through retrofitting homes to make them more energy efficient. The Warm Homes plan works differently from other schemes, in that funding is being made available through social housing and local authority grants.

How to qualify for an oil boiler grant

Oil boiler grant schemes are unique and each has different conditions you must meet to qualify.

That said, you are more likely to qualify for a boiler grant if you own the property you are applying for or are looking to replace a fossil fuel heating system with a renewable energy source.

In some cases, you may still be eligible for help with the cost of a new oil boiler if you are on a low income or are in receipt of any benefits.

Also, if your property has poor energy efficiency, you are more likely to qualify for a grant either for a new boiler or to make improvements to the energy efficiency elsewhere in the property.

Best alternatives to grants for cost savings

If you don’t qualify for a new boiler grant under any of the available schemes, it may be possible to repair your existing boiler until you can afford to replace it.

Also, some boiler manufacturers allow you to rent a boiler which can reduce the costs compared with purchasing upfront.

Installing a new boiler in the summer can also work out cheaper compared with the colder months, as there is more demand for new boiler installations in winter.

Making energy efficiency improvements to your home can also lower your energy bills, since it will always cost more to heat a home which isn’t well insulated.

Oil boiler brands & best models

New to the oil boiler market, or keen to explore all the options out there?

Compared to gas boilers, there are fewer oil boiler manufacturers to choose from. Thankfully, this doesn’t mean having to compromise on quality, performance or reliability. Likewise, there are also budget brands to consider as you’d find with other fuel types.

Best oil boiler brands in the UK (2025)

The WhatPrice team has scoured the internet to find the most popular oil boiler brands.

We looked at aspects such as the top-selling brands and overall manufacturer ratings to decide on our top 5 oil boiler brands.

Grant

Grant is a UK boiler manufacturer based in Wiltshire. The company was founded in the 1970s and has won numerous awards for its boiler technology. Its most famous oil boiler ranges include the Vortex and VortexBlue models. Grant is an excellent choice for off-grid properties including those looking to move towards sustainable and low-carbon innovations.

Firebird

Firebird employs over 150 technicians across its sites in Plymouth and Cork. For over 40 years, Firebird has been a leading manufacturer of oil boilers and has gained various accreditations relating to quality and assurance. The company claims to produce the ‘most efficient and reliable condensing boilers in Europe’.

Navien

Navien boilers have been available in the UK since 2014, with the company itself founded in South Korea in the 1970s. While the brand is not as well known as other stalwarts in the industry, users praise the highly efficient boilers with low running costs, especially when newly installed.

Warmflow

Warmflow holds the largest market share of all oil boiler manufacturers in the UK. Founded over 50 years ago, the company has a strong reputation for its oil boiler technology, particularly its Agentis range of boilers. Warmflow also provides vast options for both internal and external oil boilers giving homeowners endless options to choose from.

Worcester Bosch

Worcester Bosch is one of the most recognisable names in the boiler market. Specialising in oil combi, system and regular boilers, Worcester Bosch backs all of its oil boilers with a 7 year guarantee. On the whole, Worcester Bosch oil boilers offer exceptional efficiency within the oil boiler category.

Top-rated oil boilers & prices

We’ve researched the best oil boilers available based on aspects such as popularity and manufacturer reputation.

Grant Vortex Pro External Oil Heat-Only boiler

Replacing an old boiler is a good opportunity to consider whether switching to an external model is beneficial. If you are looking to make the switch from an internal to an external oil boiler, the Grant Vortex Pro External range is one to check out.

Available as a heat-only boiler (also known as regular or conventional boilers), the Vortex Pro External range comes complete with weatherproof casing. This boiler boasts quiet operation and low NOx emissions.

Efficiency rating: 90%
Available outputs: 15kW-26kW
Typical price range: £2,089 – £2,644

Firebird Envirogreen C35 Kitchen Regular Oil Boiler

Firebird boilers are a great choice for larger homes with higher heat demands. As the name suggests, the Firebird Envirogreen C35 Kitchen Regular Oil Boiler is designed to be installed in compact locations, including under kitchen worktops.

Some standout features of the C35 range include low NOx and blue flame burner options. The boiler itself also benefits from acoustic protection resulting in quiet operation. The Envirogreen C35 also provides front service access for easier maintenance and servicing.

Efficiency rating: 92.6%
Available outputs: 26kW-35kW
Typical price range: £1,775-£2,407

Navien LCB700 Blue Flame Internal System Boiler

As one of the few oil boilers on the market which offers a highly aesthetic design, the Navien LCB700 range of internal system boilers is made to be seen. Even when installed in the most contemporary of kitchens, this boiler range fits right in.

Backed by a 10 year warranty, this system boiler is built to accommodate high hot water and heating demands. It also has an A+ ErP rating meaning it has excellent energy efficiency.

Efficiency rating: 93%
Available outputs: 21kW-36kW
Typical price range: £1,877-£2,284

Warmflow Agentis Internal Combi

Dubbed ‘the next generation of oil boilers’, the Warmflow Agentis range is very highly regarded within the UK oil boiler market.

Warmflow claims this is not only the UK and Ireland’s only AA rated boiler, but that it can save an average of 5 litres of fuel per week compared with other leading oil combi boilers.

Among its many standout features, this internal combi boiler features a stainless steel heat exchanger and has Riello Low NOx burner technology.

Efficiency rating: 90%
Available outputs: 15kW-33kW
Typical price range: £3,337-£3,559

Worcester Bosch Greenstar Heatslave II Combi

Worcester Bosch is one of the best known names in the boiler market, which can offer peace of mind if you are more used to gas boilers.

The Greenstar Heatslave II Combi boiler range offers everything you’d expect from a Worcester Bosch boiler in terms of efficiency and performance. Crucially, there are 3 outputs (kW) available in the Heatslave II range to cater to different property sizes.

The typical warranty period of 2 years is less than other oil boiler manufacturers, although this can be extended to 5 years if the boiler meets certain installation requirements.

Efficiency rating: 90%
Available outputs: 18kW-32kW
Typical price range: £2,350-£2,395

Signs you need an oil boiler replacement

As a homeowner, the best way to know if it’s time for a new oil boiler is based on the age of your boiler. Typically, this is anywhere after 10-15 years since the boiler was installed.

Or, if you moved in after your current oil boiler was installed, your engineer should be able to advise you about the age of your boiler during your next boiler service.

However, the age of your boiler alone isn’t the only thing to consider, as there can be various other telltale signs that your current boiler is beyond economic repair.

How long do oil boilers last?

As we’ve just touched upon, oil boilers have a typical lifespan of between 10 and 15 years.

Unfortunately, if your boiler hasn’t had its annual service since it was installed, the likelihood your oil boiler could fail early increases.

Maintaining your boiler and including arranging a prompt repair of any issues can help ensure you receive many years of reliable performance from an oil boiler.

Key signs your oil boiler needs replacing

Beyond the age of your boiler, there are some other essential signs that could indicate your boiler is failing or is not financially viable to repair.

Unusual noises coming from the boiler – All boilers make noise to a degree. But if the noises suddenly seem different than before such as banging, gurgling or whirring noises, your boiler is likely failing.

Inconsistent performance – Struggling to get hot water, or does your heating seem like it’s on the blink? It’s possible bleeding the radiators or putting a power flush through the system could fix the problem. But if this doesn’t work, it could be the boiler itself which is the root cause of the problem.

Frequent repairs – If your boiler is constantly breaking down (i.e. you need more than 2 repairs in a year), it would probably be cheaper to replace your boiler.

Sudden increase in fuel bills – While fuel bills have increased for everyone, sometimes this can also indicate your system is not as efficient as it should be. Ask your engineer for advice during your next boiler service.

Alternatives to oil boilers

Since the majority of properties which have an oil boiler are off-grid, you might not have the full range of fuel options that would be available if your property was located in a more urban location.

Instead, your main alternatives to oil will involve renewable fuel sources, such as an electric central heating system powered by solar.

Given rural properties tend to have more outside space, adding renewable energy sources could prove to be a worthy investment. For instance, adding a home wind turbine to generate electricity.

Should you switch to a heat pump or biomass boiler?

Both heat pumps and biomass boilers offer sustainable fuel alternatives if you are looking to get rid of your existing oil boiler. But, as you might expect, there are some key factors to consider first.

Biomass is ideal for rural properties, so long as you have the required storage for the wood fuel. That said, compared with a gas boiler, biomass boilers are currently more expensive to run. Although, the good news is that biomass fuel is cheaper than oil which could reduce your boiler running costs.

Another option could include a ground source heat pump. Although, with average installation costs ranging between £15,000 and £30,000, ground source heat pumps require significant financial investment compared to the cost of an oil boiler replacement.

Whether you can have a heat pump installed also very much depends on the level of insulation in your property. Therefore, you may have to undertake extensive work to insulate your home before a heat pump could be installed.

Comparing oil boilers to modern heating options

Fuel type	Good for	Pros	Cons
Air Source Heat Pumps (ASHP)	Well insulated properties	Compact system which doesn’t require a flue or fuel storage. Zero emissions at point of use.	Running costs are the same as a gas boiler. Not suitable for larger homes or properties with poor energy efficiency.
Biomass	Rural properties or homeowners looking to move away from gas boilers.	Biomass is cheaper to run than oil, gas or electricity.	Storage is required for the fuel. While cleaner than gas, some CO2 emissions are generated when burned.
Electric	Small, well insulated properties with modest requirements.	Compact system with no flue or storage required. Zero emissions at point of use.	Not ideal for larger properties. High running costs.
Ground Source Heat Pumps (GSHP)	Those looking to make a long-term investment into their home’s fuel source. Rural homes are also ideal candidates.	Modern system which provides extremely reliable performance. Ultra quiet operation.	High installation costs. Requires outdoor space.
Hybrid Heat Pump	Those who want the ability to keep using oil but also have the ability to switch between a heat pump.	Great for energy savings. A less invasive installation is required.	Potential for an underutilised boiler. Existing radiator performance may be impacted.
Solar Thermal Systems	Homeowners who want to combine a compatible heating system with solar.	Generate endless amounts of energy for free!	Solar is dependent on the right conditions. It works best as a supplementary system.

Oil boilers have offered a traditional fuel system for homes which aren’t connected to the gas network. But with the prospect of oil boilers being phased out in the future, it’s worth looking at the alternatives that currently exist.

Maintenance & servicing costs

When calculating an oil boiler replacement cost, remember it’s not just the upfront boiler purchase and installation costs to consider.

That’s because all boilers require regular servicing. Often, an annual service is also a manufacturer requirement based on the warranty agreement.

Most issues should be covered under your boiler warranty. But as your boiler gets old and is no longer covered, the chances of your boiler needing costly repairs will increase.

Annual servicing costs & requirements

Across the UK, you can expect to pay between £58 and £126 for an oil boiler service.

These figures are based on our user submitted prices for boiler servicing and repairs.

What does an oil boiler service include?

During an oil boiler service, your engineer will visually inspect the boiler, boiler casing, oil tank, oil line and any other pipework or accessories. They do this to check for signs of leaks, damage or corrosion. This helps ensure your oil boiler is safe and is also running efficiently.

With oil considered a ‘dirty’ fuel, a boiler service also includes a thorough cleaning of the internal components to remove soot, sludge or debris. Your engineer will also clean the oil filter, while checking for air locks along with signs of leaks or water contamination.

The boiler will then be tested and the air-to-fuel ratio will be adjusted to ensure optimal combustion efficiency.

The flue and ventilation systems will be checked to ensure there are no blockages or corrosion.

Some users also reported to WhatPrice that their engineers bleed their radiators during an oil boiler service.

Finally, if your engineer has found any failed parts which cannot be replaced on the day, they will order these and arrange a follow-up repair.

Common Oil Boiler Problems & Fixes

If your boiler has broken down or is experiencing unusual performance, it’s time to arrange for a boiler repair.

Common issues with oil boilers which require professional evaluation include:

Loss of heating or hot water – The issue could be as simple as the oil tank having run out. Or, it could be due to thermostat issues, a tripped circuit breaker, a faulty motor, a faulty burner or an airlock in the system.

Boiler keeps turning off – The reason could be due to a safety mechanism or a fault in the system. Fixes may include pressing the reset button, cleaning the oil nozzle, inspecting and cleaning the flue or draining and replacing the oil.

Oil smell around the boiler – It’s likely you have an oil leak, but could also be due to incompatible combustion. Oil leaks are hazardous, so check for these first. Remedial steps may include replacing worn or cracked seals or getting a combustion check and adjusting the burner.

Strange noises coming from the boiler – If your boiler is old this is a sign a replacement is due soon. Steps such as bleeding the radiators, power flushing the system or topping up the boiler pressure can sometimes fix the issue.

Remember, keeping on top of your annual boiler service is the best way to avoid common issues with your oil boiler. Regular cleaning and inspection also allow your engineer to identify and remedy any issues at the earliest point.

Finding the right installer

When looking to get an oil boiler installed, you should take your time to do your research.

It’s essential the engineer is competent to install an oil boiler safely. They should also have a full understanding of the current regulations as well as how to maximise energy efficiency.

How to choose a reliable boiler engineer

It is strongly recommended to choose an engineer who is accredited by OFTEC (Oil Firing Technical Association).

The engineer should be experienced in oil boiler installations and be insured to carry out their work.

Beyond checking for accreditations on their website, also look at their online reviews. If the engineer is on the likes of Checkatrade or Trustpilot, this can help uncover honest customer reviews before inviting them to give you a quote.
Red flags to avoid when hiring an installer

• Inexperienced at oil boiler installations
• They can’t provide evidence of qualifications or insurance
• No online references or poor online reviews
• No professional website
• Pressure selling tactics
• Suspiciously low quote compared with other installers
• Refuses to carry out a site assessment before quoting
• Won’t provide a written contract
• Poor communication

Take your time to review your quotes. If something doesn’t feel right, trust your instincts.

Conclusion & next steps

Once you are satisfied with your quotes, you can then move ahead to arranging the installation of your new oil boiler.

Your engineer will visit your property to assess the scope of the job and inform you of what’s required, plus how long they expect the job to take.

Final verdict: Which boiler should you choose?

Based on the top oil boiler brands in the UK, we recommend choosing a new oil boiler made by either Grant, Firebird, Navien, Warmflow or Worcester Bosch.

To determine the best boiler make, boiler type and boiler size for your property, you will need to consult an oil boiler installer for professional advice. Get free boiler quotes and expert advice.

Oil boiler replacement cost FAQs

Have more questions about a new oil boiler cost? We’ve answered the most popular queries below.

For anything else, check out our free boiler installation and price guides elsewhere on our website.

How does an oil boiler compare to a gas or electric boiler?

To cover the functional differences between oil, gas and electric boilers, we’ve made the following table:

Feature	Oil boiler	Gas boiler	Electric boiler
Typical efficiency	90%	94%	99%-100%
Boiler types	Combi, system & regular	Combi, system & regular	Combi, system & regular
Average costs	£3,000 to £5,000	£2,000 to £3,500	£1,500–£2,500+
Space requirements	Oil tank + boiler unit	Compact for gas combi boilers. However, regular or system boilers can require additional feed tanks or cylinders	Most compact due to no external flue needed
Eco-friendliness	Not as sustainable as gas	Average. Green fuels are considered more environmentally friendly than natural gas	None at point of use (excellent if electricity is generated by solar)
Best for	Off-grid rural properties	Urban homes	Small homes with very low demands

Outside of basic differences, one of the key aspects which separates oil and gas boilers in particular is whether or not your home is connected to the gas grid or not.

Simply put, if your home is off-grid (i.e. you live in a rural location), you wouldn’t be able to get a gas boiler unless you were able to get connected by a gas supplier. The typical quote for getting connected to within 23m of the main supply is £400. However, for longer distances, the costs can be upwards of thousands of pounds.

Electric boilers don’t have the same restrictions and can be installed anywhere.

Need more information to help you choose the right boiler for your property?: Check out
The Ultimate Guide To Gas Boiler Types: Choosing The Best One For Your Home.