Gas Boiler Replacement: When and How Much?

Gas boiler with tool box

On average, gas boiler replacement should be conducted every ten to fifteen years. So when is it actually time to replace it? How much does it cost and is it worth the investment? Are there alternatives to replacing a gas boiler? How do I go about replacing a gas boiler? We answer all of these questions about gas boiler replacement and more in this easy-to-use guide.

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When Should I Replace My Gas Boiler?

A gas boiler replacement should be considered when your boiler no longer operates at peak efficiency levels. It is burning more gas than necessary, consequently, increasing your gas bill considerably. When the extra cost of gas outweighs the cost of replacing your gas boiler is when you should change.

What Sign To Look For for Replacing My Gas Boiler?


Does it seem like your gas energy bill is constantly increasing? Is your water not as hot as before? Perhaps your gas boiler is making strange noises or you’re regularly contacting your gas boiler service provider for repairs.

These are some of the common indicators that your gas boiler is no longer working efficiently and needs to have its efficiency level examined. If it is no longer running at optimal efficiency, you may need to have it replaced.

How Efficient Is My Gas Boiler?

To know how efficient your gas boiler is, you first need to look at its energy efficiency rating. You can find these labels on various energy appliances in your home. Here is what these labels mean:

  • A rating - Your gas boiler works at 90% efficiency or more.
  • B rating - Your gas boiler functions between 86-90% efficiency.
  • C rating - Your gas boiler runs between 82-86% efficiency.
  • D rating - Your gas boiler performs at 78-82% efficiency.
  • E rating - Your gas boiler operates at 74-78% efficiency.
  • F rating - Your gas boiler runs between 70-74% efficiency.
  • G rating - Your gas boiler is below 70% efficiency.

All these fancy labels for energy rating look pretty, but they don't tell us what efficiency means in terms of the actual cost. Specifically, how much money are we losing with an inefficient gas boiler?

Who rates boiler efficiency in Ireland? Since December 2011, the Home Heating Appliance Register of Performance (HARP) rates the efficiency of all home appliances used in Ireland. Gas boiler replacements must function at an efficiency of at least 90%

How Efficient Is a Brand New Gas Boiler?

Any gas-burning appliance, including a gas boiler, has very strict standards to follow. Since 2011 in Ireland, any gas boiler replacement needs to have an A energy rating.

It is important to note that there is always a bit of energy loss in a gas-burning appliance. Even a brand new gas boiler replacement will not operate much over a 90% efficiency.

As your boiler gets older, it will gradually decrease in efficiency, passing from a brand new A rating to a B, a C, and eventually all the way to a G rating. Even a regularly maintained gas boiler will lose some efficiency over time.

How Much Does an Inefficient Gas Boiler Cost?

An inefficient gas boiler will use more units of gas than necessary to heat your home and water.

Using Ireland's average gas usage for a three-bedroom house, the yearly gas cost is approximately €811 including VAT. An inefficient gas boiler, therefore, costs you the following:

Gas boiler efficiency rating Extra gas cost per year Estimated time required to pay off a new boiler
B rating - 86-90% €32 N/A
C rating - 82-86% €65 30 years
D rating - 78-82% €97 20 years
E rating - 74-78% €130 15 years
F rating - 70-74% €162 12 years
G rating - under 70% €243 8 years

What Other Costs Are Associated with an Inefficient Gas Boiler?

Beyond paying the extra gas costs for an inefficient boiler, you can also add the average regular maintenance and repairs costs of €73 per visit required for a 10 to 15-year-old gas boiler to function. It is quite easy to see why most experts agree that, on average, around 15 years is when you should be considering a gas boiler replacement.

In the graph below, we clearly depict why 15 years is the recommended age to replace a boiler. The accumulated extra cost of gas over 15 years equals the cost of a new gas boiler (around €2,000).

*For simplicity, we are using an average depreciation in efficiency of 2% per year. The line shows the accumulated cost in Euros for the extra gas used over time.

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Selectra is currently closed. You can leave your phone number and get a free callback.

How Much Does a Gas Boiler Replacement Cost?

Most companies will offer the cost of the installation in their pricing. On top of that, if you opt to have your gas boiler replacement done by your gas provider, companies such as Energia will offer you a larger discount for the replacement of your gas boiler for their existing clients.

Check Out Our Gas Boiler Guide!

Are There Any Gas Boiler Replacement Grants?


The Sustainable Energy Authority of Ireland (SEAI) not longer offers grants to upgrade or replace your gas boiler.

Since gas boilers are slowly making their way out of the market to comply with Ireland’s commitment to reach net-zero emissions by 2050 as per the Paris Agreement, now may be the perfect time to take advantage of the current grants available and make the jump to a sustainable source of heating.

What is a Heat Pump System Grant? Given the climate in Ireland, the popular choice right now is for heat pump systems over solar water heating systems. Grants for heat pump systems are available for values up to €3,500. For more information, see our complete guide on heat pump systems.

If you’re not ready to make the jump to a sustainable energy heating system, then you may want to consider a Heating Controls Grant for a value up to €700. An upgraded heating control system can help you save up to 20% on your gas energy use. Keeping our same three-bedroom example, this simple upgrade alone can bring you savings of €162

Who Is Eligible for Gas Boiler Replacement Grants?

Gas boiler replacement grants were available to all homeowners and landlords with properties built before 2011. The built date is defined by the date your electricity meter was installed. Other types of grants may also be available for homes built before 2006.

Should You Replace or Repair Your Gas Boiler?

To answer this key question, the first thing would be to determine the efficiency level at which your gas boiler is currently functioning. Despite what your label may say on the outside, it will downgrade over time and, therefore, function at a lower efficiency level.

To determine the current efficiency level of your gas boiler, simply ask your gas engineer during their next gas boiler service and use our above cost chart to see if it is time to replace your gas boiler or not.

How Do I Replace My Gas Boiler?

This will depend on which route you have opted to go with.

  1. If you opt to buy a new gas boiler, we recommend you have it done by a registered SEAI gas and oil heating installer or, at minimum, a Registered Gas Installer (RGI)
  2. If your boiler still has some life left in it and you have opted to have it repaired or serviced. Make sure you contact a Registered Gas Installer (RGI) engineer to conduct your gas boiler service.
  3. If you have decided it is time to replace your fossil fuel burning system with a sustainable heating system like the Heat Pump System or Solar Water heating system, you will first want to contact an SEAI Registered Technical Advisor.

Don't install a gas boiler yourself!A gas boiler replacement must be carried out by a Registered Gas Installer (RGI). It is illegal for anyone else to conduct the gas boiler replacement. Make sure your installer shows you their valid ID credentials.

No matter the option chosen, ensure you have a good gas and electricity plan for your home. This would be the first step en route to energy savings for your home.

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