Oil Boiler Guide: All you need to know (2023)

In this oil boiler guide, we cover how they work, how much they cost and what to expect with an oil 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 oil boiler 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 condensing 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 oil boiler prices against 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.

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Fuel Prices for Boilers
FuelCost (cents/kWh)
Gas oil7.69
Natural gas7.02
Wood pellets (bulk delivery)5.96
Wood pellets (bagged)7.21
Wood briquettes9.33

Source: SEAI

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

Oil Boiler Guide: All you need to know (5)

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 regularly have an oil boiler service.

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 oil boiler service. If you don’t have this service carried out, you could lose your warranty.

You can look at our boiler service guide for more details.

Are oil boilers being phased out in Ireland?

Oil Boiler Guide: All you need to know (6)

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.

Oil Boiler Guide: All you need to know (7)

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Pros and Cons: Is an oil boiler worth it?

Still not sure if you should opt for a condensing 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 an oil boiler service and tank verified 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.


How many Litres of oil does a boiler burn per hour? ›

As a very rough guide, a medium sized boiler could use around 3.5 litres of oil per hour when on full, whereas a large appliance might burn around four litres per hour.

How much oil does a boiler burn per day? ›

As this heat transfer occurs, the furnace or boiler has to work overtime to keep the inside of the house warm. Daily heating fuel oil consumption can range from 1-2 gallons on a warm winter day in a smaller house, to 10-20 gallons on a really cold day in a large house!

How much oil should a boiler use per month? ›

On days when the outside temperature averages 50 degrees Fahrenheit, a typical household will consume 2 gallons of heating oil. When you divide a full 275-gallon tank by two, the heating oil will last for approximately 137 days, or four months and two weeks.

What temperature should a oil boiler be set at? ›

Going for something between 180 and 200-degrees Fahrenheit is recommended. Households that like to keep it warm should still limit themselves to 200 degrees as the maximum temperature setting. Moving higher than 212 degrees may cause the boiler to start overheating so keep a safe distance from this figure.

How long should 500 Litres of oil last in winter? ›

500 litres, even in winter, will last us 2-3 months. We have a pretty big house, underfloor heating throughout the whole of the downstairs which is on 24/7 throughout the winter and central heating upstairs which is on morning, evening, through the night for an hour and any other time it's needed.

How Long Will 1000 Litres oil last? ›

1000 litres of heating oil may last one home a year, and it may last one family three months.


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