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Oil Boiler Replacement Guide


Gas boilers are dominant in the UK market. But, for homes that are not connected to the gas grid, there needs to be alternative sources of power to keep their homes warm and hot water running. One of the alternatives is oil boilers.

Oil boilers are an excellent alternative for various reasons. They are affordable, run great, and are very reliable. Even though oil boilers are not as common, the process of choosing the right one for your home is just as tedious and time-consuming as looking for a gas boiler.

You can save yourself the trouble and time and quickly go through this guide, and in a few minutes, you will have all you need to know about oil boilers to buy one successfully.

What is an Oil Boiler?

An oil boiler is very similar to a gas boiler. The only significant difference is that the oil boiler uses oil instead of gas.

Oil boilers can come in two types. There are combi and regular oil boilers. Each of them is the same as the gas variety and uses the same principle of heating.

For an oil boiler to function, you need to have a reservoir to hold the fuel. The reservoir is often placed outside the house in the garden or underground. You also need to have a supplier to deliver the oil since the oil is not piped to the house.

How Does an Oil Boiler Work?

Oil boilers are quite similar to other fuel types of boilers. The boiler lights up the oil to produce heat energy that is absorbed by the heat exchanger, which heats cold water from your mains or storage tank.

Once the water is hot enough, pumps in the boiler pump it through the radiators around the house to make it warm. If the oil boiler is conventional, the pumps will direct the water to the storage tank. On-demand, the water will move from the tanks to the areas of demand.

To keep the supply of oil consistent, the oil boiler has a storage tank. One refill of the oil tank is enough to keep the boiler in operation for 6 to 9 months. The tanks come in different sizes. However, if you want a tank with a capacity of 3,500 litres or more, you have to make sure the tank complies with building regulations and the installation must be handled by professionals.

To reduce pollution, most oil boilers use 28sec oil which is known as kerosene, which has fewer emissions. There has also been a growing trend using bio-heating oil produced from vegetable oil. However, this avenue is still being explored. Should it be realised, it would make oil boilers more environment-friendly.

Advantages of an Oil Boiler

High efficiency

Most oil boilers have a Grade-A ErP rating. That means that you will have fuel for longer, and you will be putting money back in your pocket from energy savings.

Excellent heat transfer

Oil boilers have excellent heat transfer. They have a 2nd and 3rd pass tubes that ensure the water gets enough heat as it passes through them. The superior thermal transfer saves the boiler from strains, which ensures you get the best results, and you avoid putting too much stress on the boiler.

Lower running costs

An oil boiler will cost less to run. The annual savings on using an oil boiler are between £100 and £300. However, the savings will also depend on how efficient the current boiler is.

Easy to maintain

Most types of boilers have complicated designs that make maintenance and service pain. The same is not the case for oil boilers. Oil boilers require commissioning after installation, which means the boiler works at the highest efficiency and is easy to maintain.

Oil boilers for all occasions

With gas, LPG and electric boilers, you might not have much of a choice but to give up some of the space in your home. With an oil boiler, if the boiler can’t be sited inside the house, you can go out and buy an external oil boiler that can sit outside. With external boilers, you get the same benefits and efficiency you get from internal ones only that you don’t have to give up the extra space inside the house.

Disadvantages of an Oil Boiler

Everything on the face of the world that has an advantage has a disadvantage as well. Great as oil boilers might be, they are not immune from this rule. Some of the downsides of owning an oil boiler include:

Fluctuating oil prices

Like gas, the prices of oil are always fluctuating based on a variety of factors like weather conditions, demand and political stability. You might find yourself buying the fuel when the prices are higher, which might cause a little more damage to your pockets.

Refills take time

Even though technology has done a lot to help avoid scenarios where the fuel runs out without your knowledge, your boiler has to be compatible and installed with such technology. If you don’t have it, your boiler fuel could run out at any time and you have to wait until it is refilled again.


If you don’t have an oil-powered central heating place, the pipework can be costly and disruptive. Also, the oil tank is not appealing if it is not installed underground.

Now that you know the benefits and downsides of owning an oil boiler, you are better equipped to decide on whether an oil boiler is something you would want to explore. Other than the fluctuating cost of fuel, most of the other disadvantages have possible solutions.

How Much Does an Oil Boiler Cost?

The cost of an oil boiler will vary greatly based on a few factors. These include:

The type of boiler

Oil boilers come in two types; Combi oil boilers and conventional oil boilers. Each of the types is uniquely built to serve different purposes. With that said, the cost will vary depending on which kind of oil boiler you want for your home.

Output rating

You don’t have much say on the output rating of the boiler you can buy for your home. The ideal rating is often determined by considering the size of your house, the number of showers, among others. Nonetheless, the output rating is a crucial determinant of the cost of the boiler. The higher the output rating, the more your boiler will cost.

Energy efficiency

Boilers with higher efficiency will often cost more compared to those with low efficiency. But they can make the money back in terms of energy bill savings.


Some brands have higher price tags than others. When choosing the boiler, what matters more is the quality and reliability of the boiler. However, it’s also public knowledge that some brands are more dedicated to producing quality, long-lasting boilers than others.

A small combi oil boiler will cost you £2,000 to £2,500, while a large combi oil boiler will cost anywhere in the regions of £3,000 inclusive of installation. Expect to spend about £1,200 to £2,600 for a small heat only oil boiler and up to £3,800 for a large and high output oil heat only oil boiler.

A system oil boiler will cost between £2500 to over £3,500. Internal condensing system oil boiler systems will typically cost more.

Other than the cost of the boiler, you should also be worried about the cost of installing the boiler. Boiler installation costs are high and make up a substantial percent of your budget. Unfortunately, because the installations are never the same, the cost of installation is notorious for fluctuating.

The cost of installation is even higher when you don’t have the appropriate pipework installed. The cost of installation for an oil boiler can range between £3,000 to £5,000.

You can get a FREE quote from installers in your area by filling a short inquiry form. The installer will give you a call and provide you with the accurate, no-obligation quote. You can use the quote to compare prices with other installers or use it to come up with your budget for the new boiler and installation.

What is the Running Cost of an Oil Boiler?

Now that you have done most of the due diligence in finding an appropriate boiler for your home, the next challenge is trying to figure out how much you will spend annually to keep the boiler running.

On average, expect to spend around £1,355 to heat a three-bedroom house all year. For a gas boiler with the same specifications, you would spend around£770 to £950, while an LPG boiler of the same specs will cost you about £1,300.

While on the surface, the figures are against oil, it is the more efficient fuel and offers a good return for money per unit of energy.

It’s also worth noting that the price of oil fluctuates and with a little luck, you might buy the fuel at a lower price, which would help you make even more savings.

What is the Best Oil Boiler?

Grant VortexBlue

Grant Vortex is known for quality, easy to install boilers. They have a wide range that covers all types of boilers and have wall-hung and floor-standing varieties as well.

The Grant VortexBlue is one of the best internal combi oil boilers they have on the market. It has an efficiency rating of 91.7%, which is a grade A rating and has a grade B rating for hot water.

The VortexBlue comes in various outputs, including 12, 26, and 36kW, to give you the freedom to pick what works best for you.

Firebird Envirogreen Kitchen

It’s hard to pick one boiler from this range. Each of the boilers is carefully designed to serve it’s purpose and is a joy to anyone who cares to have it.

This range of regular oil-fired boilers come with different outputs starting from about 12kW up to 100kW.

All the boilers in this range have a Grade-A ErP rating with rating efficiencies all above 91%. That gives you comfort, knowing that you will save money on your energy bills.

Warmflow Utility HE System Boilers

Last on the list of some of the best oil-fired boilers in the market is the Warmflow Utility HE system boiler. The boiler is available in various outputs ranging from 15 to 44kW. It is compact and will fit under ordinary kitchen working surfaces and has a nice pre-coated white case.

All the three models in this range have a Grade-A ErP rating with factory fitted condensate traps to ensure complete safety and compliance.

If you’re looking for quality and value for your money, this range of boilers built from quality materials will offer exactly that.

How Do I Maintain an Oil Boiler?

Without the right treatment and maintenance, even the hardiest oil boiler will be limited to how long it can give you good service. Proper maintenance and servicing of the boiler will ensure the boiler remains efficient and performs well for long.

When it comes to boilers, the safest approach is to let professionals handle them. Boilers of all types can be dangerous if not handled by a qualified and experienced boiler engineer.

In the case of oil-fired boilers, you want to find an OFTEC (Oil Firing Technical Association) certified installer to install and service the boiler.

Compare the Boiler Market has hundreds of OFTEC engineers in your area and we can help you find the right one for your new boiler.

What is the Difference Between an Oil and LPG or Gas Boiler?

There are several differences between oil, gas and LPG boilers. These differences are what make each of the boilers unique in their operation.


The first difference between the three types of fuel is the cost of fuel. Gas is the most affordable, followed by oil and LPG, is the most costly.

With that in mind, you can expect to spend more when running an LPG boiler compared to running an oil-fired boiler. Even with the fluctuations in price, the cost of LPG typically remains higher than that of oil.

Installation and heating costs

The other difference is in the installation costs. Oil boilers are the most expensive to install. They cost between £1,500 and £3,000 to install. You can get an LPG boiler up and working with as little as £400.

Because LPG costs more, running the boiler will cost you more compared to someone running an oil boiler. In terms of running costs, gas boilers are the most pocket-friendly because gas is more affordable.

You will also spend less installing a gas boiler because it doesn’t come with the fuel tank and the additional pipework required for this.


An area where LPG boilers have the upper hand on oil boilers is the fact that LPG can be used to run various other things in your house like an oven. This allows you to strike multiple birds with one stone. On the other hand, oil only works with the boiler and nothing else.

If you already have an LPG tank on-site, you could hook it up to your boiler and save on the cost of buying another tank.

Environmental Friendliness

LPG has a smaller carbon footprint compared to oil. However, oil boilers are a tad bit more efficient. However, LPG is superseded by solar and wind turbines as a power source for your boiler. These will make great alternatives if your focus is to get the most environmentally friendly boiler.

The question of which of the three types of boilers is ideal depends on the situation you are in. If you’re not living off the grid, gas boilers are the best. That is a no-brainer. But, if you’re off the grid, you have a few more considerations to ponder on before you settle on the right boiler.

Get Free Quotes for Your Boiler Replacement Today!

Finding the right oil-boiler for your home is just one part of the puzzle. The installation of the boiler is the other part. Proper boiler installation is key in ensuring you can enjoy the best performance and efficiency of your boiler.

Finding the right OFTEC engineer for your boiler and also getting competitive prices can be a challenge. Compare the Boiler Market can help to connect you with reputable, qualified and OFTEC certified boiler engineers and also help you get up to three FREE, no-obligation quotes.

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