Oil Boiler Guide: All you need to know

In this oil boiler guide, we cover how they work, how much they cost and what to expect with a boiler service. We also cover frequently asked questions about having and installing an oil boiler.

How does an oil boiler work?

An oil boiler works by igniting oil in a combustion chamber. This produces hot gases that are then passed through a heat exchanger (usually a copper coil) to heat water. This heated water is pumped around the home to your radiators, taps and showers when it's required.

An oil boiler is very similar to a gas boiler except it needs oil to function instead of gas. The oil must be regularly delivered to the home in a tank. The oil is held in this storage tank until it is needed for heating and hot water.

There are three types of oil boilers:

  • Regular oil boiler – This type of oil boiler is often called a conventional boiler. It requires having two separate components: a hot water storage cylinder and a cold water storage tank. A regular oil boiler is best for homes that have low water pressure or more than two bathrooms.

  • Oil combi boiler – With an oil combi boiler, cold water is fed straight into the boiler and heated on demand. It requires neither a cold water tank nor a hot water storage cylinder, thus making it ideal for small spaces. This type of boiler can help you save on hot water costs since there is not a constant hot water supply.

  • Oil system boiler – A system boiler is basically an upgraded version of a regular boiler. It requires a hot water cylinder, which means it is good for homes with high hot water demands. Water is supplied to the boiler via the mains, so you do not need to have a cold water storage tank.

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How efficient is an oil boiler?

Modern oil boilers can have efficiencies of around 85% to 95%. A new condensing oil boiler will typically have an efficiency of at least 90% while a non-condensing oil boiler will be around 85% efficient.

Older oil boilers tend to be 60% to 70% efficient. Boilers decrease in efficiency as they age, so the longer you have it, the less efficient it becomes.

You can follow the tips below to improve the efficiency of your oil boiler:

  • Use room thermostats
  • Use a boiler interlock to prevent short cycling when you don’t need heat or hot water
  • Use a cylinder thermostat for the hot water tank
  • Programme heating and hot water separately
  • Place thermostatic radiator valves on radiators

Want to make your home more energy efficient? Check out our 101 tips on ways to save energy and start reducing your bills today.

Oil boiler prices: How much is a new oil boiler?

A new oil boiler will typically cost between €1,300 and €3,000. The price depends on the following variables:

  • The manufacturer
  • The boiler model
  • The capacity of the boiler

A less powerful oil boiler will be cheaper than a high-capacity boiler. The size of your home and your hot water demands determine the size oil boiler that you will need.

If you are replacing one type of oil boiler with another type (such as swapping a system boiler with a combi boiler), you may need to pay additional costs. These costs could include installing or removing the hot water cylinder or cold water storage tank.

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Can you install your own oil boiler?

You should hire an Oil Firing Technical Association (OFTEC) engineer to install your new oil boiler for you. Even though this is not a legal requirement, it’s recommended in order to ensure the safety and quality of the installation.

OFTEC engineers have completed approved training courses and must periodically take assessments to make sure they are up-to-date with the best practices. Once the OFTEC engineer has installed your new oil boiler, they will give you a certificate that confirms the work carried out meets industry standards.

What kind of oil is used in an oil boiler?

Most oil boilers in Ireland use kerosene oil. It’s cleaner to burn than heaviers oils (such as gas oil) and is also more efficient. Research is currently underway to find a more sustainable alternative to kerosene oil.

Are oil boilers expensive to run?

Running an oil boiler tends to cost about the same as running a gas boiler. In the following table, you can compare the prices for different types of fuel.

Kerosene is the main fuel used to run oil boilers in Ireland. Gas oil is more popular in most other European countries.

Fuel Cost (cents/kWh)
Gas oil 7.69
Kerosene 7.57
Electricity 26.16
Natural gas 7.02
Wood pellets (bulk delivery) 5.96
Wood pellets (bagged) 7.21
Wood briquettes 9.33

Source: SEAI

For more information about how much it costs to run an oil boiler, head to our complete guide on home heating oil.

Can I get a grant to replace my oil boiler?

There are no grants available for a replacement oil boiler. The Sustainable Energy Authority of Ireland (SEAI) used to offer a grant for a new oil boiler through the Better Energy Homes Scheme. This scheme was revised in 2018 to no longer include grants for oil or gas boilers.

Pile of money

The scheme currently provides grants for the following:

  • Up to €3500 for a new heat pump system
  • Up to €1200 for solar thermal systems
  • Up to €700 for upgrading your central heating controls

How long should an oil boiler last?

A typical oil boiler will last for 15 to 20 years. To ensure it runs for as long as possible, you should properly maintain and service your oil boiler regularly.

Oil boiler service

As with other heating systems, you will need to service your boiler regularly. Doing so is important for the following reasons:

  • Ensure safety — OFTEC engineers will check the system to make sure you and your family aren’t being exposed to poisonous fumes.

  • Maintain efficiency — A regular boiler service ensures your oil boiler is running at its maximum efficiency. This also ensures lower energy bills.

  • Avoid a breakdown — Regular servicing helps you to prolong the life of your boiler and avoid having to pay for expensive repairs. A properly maintained boiler could last for up to 20 years.

  • Keep your warranty — Many boiler manufacturers require you to get an annual boiler service. If you don’t have this service carried out, you could lose your warranty.

Let’s now have a look at some common questions people have about servicing their oil boiler.

How do I service my oil boiler?

You should hire an OFTEC engineer to carry out the oil boiler service for you. The engineer will check and clean all components of the oil boiler.

Before the engineer leaves, you should confirm they have done everything on their boiler service checklist. If possible, get these steps in writing. This will come in handy if there are any problems and the manufacturer wants to check you have properly had the boiler serviced.

The oil boiler service should include the following:

  • Checking the safety of all parts
  • Check for any leaks in the pipework
  • Check the gases that are pumped out by the flue
  • Check there is no water in the oil storage tank

How much does it cost to service an oil boiler in Ireland?

An oil boiler service typically costs €60 to €100. The price of the oil boiler service can vary depending on the following:

  • The type of oil boiler that you have
  • The location of where the service where the boiler service will be carried out

Before getting an oil boiler, check with the manufacturer and your energy supplier to see if they could carry out the service for you. The annual service may also be included in your boiler insurance.

If you decide not to get your oil boiler serviced, it could end up costing you more in the long run if your boiler breaks down or requires an expensive repair.

How often should an oil boiler be serviced?

An oil boiler should be serviced every 12 months. This will ensure that the boiler is running safely and efficiently.

Are oil boilers being phased out in Ireland?


The installation of oil boilers in new builds will be banned from 2022. Gas boilers will also be banned in new builds from 2025. These new regulations do not affect homes that currently have oil boilers, and oil boiler replacements will still be available.

The move comes as part of the Government’s Climate Action Plan 2019, which put in place actions to reduce the use of fossil fuels in order to move towards a green future. The Government aims to generate 70% of our electricity with renewable resources by 2030, so banning oil boilers is part of reaching this larger target.

For the time being, these new new rules in Ireland will only affect new homes.

What will replace oil boilers?

The Government’s aim is for heat pumps to replace oil and gas boilers. Air source heat pumps are typically 300% to 350% efficient. This is more than three times more efficient than most oil boilers!

Since heat pumps are so efficient, swapping out your old oil boiler for one will likely produce significant savings on your energy bills.

Green energy can be just as cheap as normal energy. Switch today with Selectra.Call us for free and talk to one of our energy advisors to get the cheapest deal on the market right now. Call 1800 816 036 or get a free callback now.

Pros and Cons: Is an oil boiler worth it?

Still not sure if you should opt for an oil boiler or go with a different type of heating system? We break down the pros and cons of having an oil boiler so that you can decide if having one installed is worth it.

Pros of having an oil boiler

  • It’s a good alternative for individuals that live off the mains gas grid.
  • Oil is an efficient fuel. Most modern oil boilers are more than 90% efficient.
  • It’s easy to have a replacement oil boiler installed.
  • Oil is not as prone to explosion when compared to gas.
  • Oil doesn’t emit carbon monoxide when burned.
  • You can easily stock up on fuel when oil prices are low.
  • You’re free to change your supplier whenever you want.
  • Oil boilers work well in combination with renewable sources (such as solar power).

Cons of having an oil boiler

  • Oil prices can easily fluctuate depending on global factors.
  • Oil boilers produce more carbon dioxide than gas boilers.
  • You need to monitor the tank level and remember to refill it before the supply runs out.
  • You will need to have the oil boiler and tank serviced every year.
  • Having one installed for the first time can be quite expensive.
  • Oil boilers will be banned in new builds from next year.
  • You have to have enough space to store an oil storage tank.
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