Condensing Boilers: Are they worth it?

Repairman with condensing boiler

Condensing boilers, colloquially called “condenser boilers”, have been mandatory in Ireland since 2005 and continue to be the fuss of the home energy market. In this guide, we’ll examine everything you need to know and more about condensing boilers. What is different about a condensing boiler? Are they any good? How much do they cost and, therefore, are they worth it?

What is a condensing boiler?

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In layman's terms, a condensing boiler re-uses some of the waste produced from the gas or oil used to heat your water. In doing so, it has an efficiency rate as high as 98% compared to a traditional non-condensing boiler, which may function anywhere between 70-80% efficiency.

Condensing boiler, condenser boiler, or condensate boiler?

You probably have heard all three terms used and wonder what the difference is between them. There is none. Condensing boilers, condenser boilers and condensate boilers are just different terms people sometimes use when referring to condensing boilers.

How do condensing boilers work?

Any gas or oil boiler emits fumes (mainly water vapor or steam) that evaporate through the flue. If you have a non-condensing boiler, these fumes or gases are lost and are considered unused or wasted energy.

A condensing boiler simply re-sends these fumes into the system to extract maximum usage from every drop of gas or oil used, so much so that condensing boiler manufacturers allege they can reach as high as 98% efficiency. This level of efficiency implies savings of around €146 per year on the average gas bill.

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Are condensing boilers any good?

With such savings provided by condensing boilers, it should be no surprise to understand why, since 2011, the Sustainable Energy Authority of Ireland (SEAI) has mandated all gas or oil boiler replacements must meet 90% minimal efficiency.

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Consequently, all new gas or oil boilers are condensing boilers. Non-condensing boilers are no longer allowed to be installed in Ireland as they do not meet the required efficiency levels.

Even though they are more efficient, it doesn't mean condensing boilers do not have their drawbacks.

For starters, even though they appear ‘greener’ due to their higher efficiency, they do emit a different waste. Specifically, an acidic liquid that needs to be disposed thru a waste pipe or drain.

The extra plumbing required to dispose of this waste, as well as the often larger piping required for the flue, can make for a rather complex installation. If a condensing boiler is not installed properly, it can cause a lot of problems.

Warning! Always use a Registered Gas Installer (RGI) for a condensing gas boiler installation and an Oil Firing Technical Association (OFTEC) engineer for condensing oil boilers.

Condensing boiler advantages

  • Highly efficient - This means large savings on your gas bill
  • Lower gas emissions - Less CO2 emissions means better for climate change.
  • Easy to integrate - They can fit into your existing gas boiler system easily.

Condensing boiler disadvantages

  • Extra plumbing required - Requires both a flue and a waste pipe or drain
  • Costly to repair & maintain - Extra plumbing means more cost if it breaks down.
  • Still has toxic waste - Although better for CO2 emissions, it releases an acidic liquid that needs to be disposed of.

What is the difference between a combi boiler and a condensing boiler?

In actuality, there is no difference between a combi boiler and a condensing boiler.

A combi boiler is a type of condensing boiler which provides hot water on-demand. These are usually ideal for smaller homes with little space available.

There are also regular condensing boilers and system condensing boilers. Both of these systems require a cylinder tank where the hot water is stored. These are usually ideal for larger homes where space is not an issue.

See our gas boiler guide and oil boiler guide for more details on the different types of boilers.

Is my boiler a condensing boiler?

There are a few things you can quickly look at to know if your boiler is a condensing boiler.

  • Check the installation date - If your boiler was installed after April 2005 then, it is a condensing boiler as this is when legislation mandated all boilers be condensing.
  • It has a plastic pipe - If you notice a plastic pipe leading to a drain, your boiler is definitely a condensing boiler.
  • Check the flue - Is the flue leading out of your home, through the exterior wall or roof, made of metal? If so, it is another indicator you may have a non-condensing boiler.

How much is a condensing boiler?

Condensing oil boiler prices vary a lot. The price will first depend on your home's current system, such as if you have a combi, regular or system boiler.

It is much easier and cost-effective to replace your existing boiler with the same type of boiler system.

From there, you would have to look at different brands of condensing boilers. We look at two of the more popular condensing boiler brands in Ireland below.

Firebird Enviromax condensing boilers

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Firebird boilers have been trading in Ireland for over 40 years. The company, O’Donovan Enterprises Ltd, is based in County Cork and their products continually receive excellent customer reviews.

The company was one of the first to manufacture condensing boilers with their launch of the Firebird Enviromax line back in 2005.

They offer a wide range of products in their Firebird condensing boiler line. There are over 60 types of boilers, from the C26 to C58 models, that address the specific needs of each individual home.

Firebird condensing oil boiler prices can range anywhere between €1,600 to €3,000 including VAT depending on the size and type required for your home.

Grant Vortex condensing boilers

Founded in 1978, Grant launched its Vortex condensing boiler line in 2002, years before the competition. So innovative was the product that it won the H&V news (UK) domestic product of the year award in 2003.

Operating out of County Offaly, Grant also offers over 60 types of condensing boilers to address the specific needs of each home in Ireland.

Grant Vortex condensing boilers range from 15-70kW outputs to 26-36kW. Condensing oil boiler prices range, according to their output size, between €1,200 to €2,200 including VAT

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Are condensing boilers going to be banned?

Both gas and oil condensing boilers will be prohibited in any new builds as of 2025. Ireland has also signed the Paris Agreement accord, which promises to reach carbon net-zero emissions by 2050.

Although this may seem like a very distant future. When you consider the shelf life of any new condensing boiler is approximately 15 years, this may be the last time you can replace your existing boiler before being required to change to a net-zero emission system.

This leads to the almighty question:

Condensing boilers: Are they worth it?

Whether condensing boilers are worth having or not will depend on the individual situation and the budget you have. Let's weigh the pros and cons of keeping your condensing boiler versus changing to a different option.

Pros and cons of having a condensing boiler system

Since it is still permitted to use condensing boilers and the deadline for changing them is far away, why not wait for a little while longer to change?


  • Cost-effective - In the short term, it is likely more economical to simply repair, service, or replace your existing condensing boiler system. Basically, if it ain't broke, why fix it?
  • Fewer hassles - Who wants to have lengthy renovations done to swap out an entire heating system?
  • Technology improvements - By ‘waiting it out’, you allow yourself the time to see what new technologies and heat source alternatives may arise. There may be something around the corner that will outperform anything currently available.


  • Missed opportunity - The future is uncertain, there is no guarantee that future grants will be available. Replacing heating systems in the future could therefore be even costlier than it would be today.
  • Not so green - Although condensing boilers are better for the environment than non-condensing. They still use a non-renewable source of energy. To continue to use one will continue to harm the environment.

Pros and cons of changing heating system

If you consider that all gas, oil, and fossil fuel boilers will eventually be replaced, why not make the jump today and get it over with?


  • Grants available - You can receive as much as €3,500 by changing to a Heat Pump System and €1,200 towards a Solar Water heating in grants from the Sustainable Energy Authority of Ireland (SEAI).
  • Green - By changing now, you are already doing your part towards a sustainable future. Your kids, grandkids, will be grateful.
  • Efficiency - Any fossil fuel boiler, condensing or non-condensing, will never reach 100% efficiency. In fact, it is often much lower. Switching to a different system, such as an electrical boiler, will allow you to reach 100% efficiency and therefore, lower your overall energy bills.


  • Costly - Any change in heating systems, even with the help of a grant, can be costly.
  • Hassle - No one likes to have hefty renovations done to a home that can last multiple days.
  • Missed opportunity - The future is uncertain, electrical boilers, heat pumps, and solar water heaters are some of the current front-runners in terms of alternatives. But how frustrating would it be to make the jump only to have a new more efficient technology arise soon after making the change!

Bottom line, there will always be a bit of a gamble with either option. The only thing within your control is ensuring your heating system is well maintained and ensuring you have a great plan for your energy bills.

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