What is a Combi Boiler? Full Guide 2023

What is a Combi Boiler? Full Guide 2023

combi boiler control pad

If you’re keen to bring down your monthly energy bills and start living more efficiently, it’s time to think about having a combi boiler installed. If your current system is lacking efficiency or your gas boiler is not firing up, a low-maintenance combi model is an obvious choice.

What is a combi boiler and how much is it going to cost you? As well as being easy to install, combi units are among one of the more affordable boiler systems around. In short, if you’re looking for cheaper energy bills, fewer breakdowns and a steady supply of hot water, there’s no better choice. 

What is a Combi Boiler? 

Combi boilers, sometimes referred to as combination boilers, are a common sight in Irish households. They’re an energy-efficient choice for anyone looking for something that’s central heating compatible and provides hot water on demand. They’re particularly well-suited to smaller properties and family homes, with these compact units taking up far less space than a conventional water cylinder or storage tank.

Although most combi boilers still use gas, you’re only using fossil fuels when you must. This makes combi boilers far more cost-effective than older boiler units. Installing them is straightforward and they require very little maintenance. 

How Does a Combi Boiler Work? 

the process of a gas combi boiler

Image credit: https://idealheating.com/

Because combi boilers are so reliable, it’s easy to forget about what’s going on under the hood. Whenever you turn your central heating system on or turn on a hot tap, the gas boiler inside the boiler ignites. This burner flame produces heat, which is captured by heat exchangers and transferred to the primary circuit of the boiler. Now, the heat is ready to be transferred through your home. This can be through your central heating pipework to your radiators or water taps via another heat exchanger. Preheat systems are a standard feature of many contemporary boilers. This means your taps will always have a reserve of hot water to draw from.

Although they tend to look indistinguishable from one another, there are a few different combi boilers available. Natural gas combi boilers are the most common, with these systems pulling fuel from the national grid. There are also liquid petroleum gas (LPG) boilers. Compared to natural gas, LPG is a clean and cost-effective fuel. However, they’re only an option if you have the space for LPG storage tanks.

What is a combi boiler going to do that other systems can’t? If you’re searching for maximum energy efficiency, an electric combi boiler is the way to go. With an electric combi boiler, there’s no energy waste whatsoever as water is heated. The major drawback of this type of combi boiler is that electricity is far pricier than natural gas.

Struggling to make sense of the combi boiler vs. system boiler dilemma? The key difference here is that system boilers require far more storage. While combi boilers draw water directly from the mains, a system boiler needs two separate storage tanks for water, including a cold water storage tank. While these tanks can be stored in loft space, not every property has sufficient space for them. Despite their drawbacks, system boilers are worth considering if you’re suffering from low water pressure.  

How Much is a Combi Boiler in Ireland? 

What is a combi boiler going to set you back in 2023? Currently, the cost of replacing a gas boiler with a combi boiler in Ireland will cost you in the region of €2600. However, many different factors can affect the cost of installation. If you opt for a cheaper brand and model, expect significantly lower combi boiler prices. You’ll also need to think about the kind of system you’re looking to replace.

Do you need to revamp your system and move your boiler to a new floor or corner of the home? Shifting the location of your unit can also impact the cost of combi boiler installation. If you’re thinking about integrating smart home features, you should also expect to pay a premium for installation.  

Combi Boiler Pros and Cons 

So, what is a combi boiler going to give you that your current system can’t? Below are some of the main benefits and drawbacks of combi systems.  


Hot Water On Demand 

Traditional boilers are limited by how much can be stored in a hot water tank. With a combi boiler, you’ll always have a steady supply of hot water when you need it, with water drawn from the mains supply itself.  

An Energy Efficient Choice 

Running a home costs money, with a substantial part of that spent going on heating. While rising energy costs are a fact of life, you can control how much you’re spending by choosing an energy-efficient combi boiler. All new combi boiler installations will come with an energy efficiency rating of at least 90%. This means far less energy is wasted to heat your home and provide you with hot water.  

They’re Low Maintenance 

Although they’re more cost-effective and efficient than traditional boilers, combi units have a comparatively simple design. With less pipework to worry about, fewer things can go wrong with your combi boiler. A yearly gas boiler service should do the trick. 

Most Compact Solution Around 

Without any cold storage water tanks or cylinders to worry about, combi boilers are ideal if you’re looking to free up precious storage space in your kitchen or airing cupboard. These compact boiler models are also the perfect solution for small homes and apartments. 


Low Water Pressure is a Problem 

If you live in an area with poor water pressure, you may need to invest in pump installation to get the most out of a combi boiler. This can make the overall cost of combi boiler installation rather expensive.  

Not Ideal for Larger Households 

While combi boilers are perfect for smaller homes, they may struggle with demand in larger households. If your home has more than three bedrooms and several bathrooms, the amount of hot water your combi boiler can produce may fall short.  

No Backup Systems 

Another potential downside of combi boilers is that they don’t include a conventional immersion heater. In the unlikely event of a boiler breakdown, this means you won’t have any backup hot water available until the issue is resolved.  

Where Can a Combi Boiler Be Installed? 

As well as being a more energy-efficient choice of gas boiler replacement, combi boilers are a low-profile option. Thanks to their discreet design and dimensions, combi units can be concealed in cupboards, making them an ideal choice for compact kitchens. They’re also suitable for larger bathrooms, utility rooms and garages.

If you have a big enough loft, a combi boiler can also be installed in this unused space. If you live in an apartment and don’t have the luxury of loft space, even spaces like bedrooms can be used for combi installation. As most new models are incredibly quiet, a functioning boiler won’t cause any issues for your sleep schedule.  

How Long Does Combi Boiler Installation Take? 

Replacing an outdated combi boiler with a new one is relatively straightforward. A plumber in Cork can replace an existing unit with a like-for-like model in just a few hours. Looking to make the switch from an old gas boiler to a combi model? More complex tasks are involved, which can lengthen installation timelines.

If you’re thinking about changing the position of your boiler, you can also expect a longer installation timeline. Moving a combi boiler to another floor or room may take between 1-3 days, although a pre-installation survey will flag any major issues that might cause a delay.  

Is a Combi Boiler Right for You? 

There are many reasons to make the switch from an outdated gas boiler to a combi one. If your current boiler is older than 15 years, it’s long overdue for a replacement. Even an older combi boiler will prove very inefficient when compared to a new model. Looking for a unit that requires less maintenance and uses far less energy to heat water? A compact combi boiler is the way to go.

While there’s not always the best choice for larger properties, combi boilers will comfortably fulfil the requirements of smaller households and single-person residences. They’re generally cheaper and far easier to install than other types of boilers.  

Thinking About Combi Boiler Installation? 

In the market for a new boiler? If your current system is outdated and requires constant repairs, it makes complete sense to switch to an energy-efficient combi boiler. Not sure what model to go with? At Complete Plumbing Solutions, we can talk through your requirements with you and advise on the best combi model for your needs. Once you’ve made the switch, you’ll be able to enjoy instant hot water and significant savings on your monthly energy bills.

Ready to make the upgrade? Speak to the team at Complete Plumbing Solutions today. Along with combi boiler installation, our team can help with annual gas boiler service and respond to emergency callouts. 

Looking for general plumbing repairs or want to talk about power flushing? We can help. Need to find a plumber in Mallow or learn more about pump services? Our experts are ready and waiting to talk. Call us on (085) 169 4244 or schedule a callback today. 

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