Condensing boilers are ultra-efficient. Combi boilers are ultra-efficient. When you mix the two together, bill-saving magic happens.
- What is a Condensing Boiler?
- How Do Condensing Boilers Work?
- What is a Combi Boiler?
- How is a Combi Boiler, Condensing?
- Condensing Boiler Regulations
- Advantages of a Condensing Combi Boiler
- Disadvantages of a Condensing Combi Boiler
- How Much Does a Condensing Combi Boiler Cost?
- What Size Condensing Combi Boiler Do You Need?
What’s the difference between a condensing boiler vs a combi boiler? It sounds like the lead-up for the world’s most efficient joke, but it’s a real question for many people.
If you are on the hunt for a new boiler for your home and have come across these two terms, you may be wondering what the difference is?
And which you should choose for your home?
SPOILER ALERT! They are ultimately the same thing. In fact, all modern boilers are condensing boilers, whether that be a combi, system or a regular boiler. Another spoiler: Darth Vader is Luke Skywalker’s father.
You no longer need to be concerned about avoiding a non-condensing boiler, since legislation banned their sale in the UK back in 2005.
Want to know which condensing combi boiler is best? Check this out.
What is a Condensing Boiler?
The term "condensing" relates to the technology the boiler uses and in the past all boilers were non-condensing.
In this old design of the boiler, all of the hot waste flue gases were released outside of the home, which itself wasted a substantial amount of heat and therefore money.
It also released a significant amount of carbon emissions, a greenhouse gas that’s partly responsible for climate change. Apparently, both flatulating boilers and cows are bad for the environment.
In response to increasing energy costs and environmental concerns, Boiler Plus legislation was established in 2005.
This meant that from then on all new boilers had to use condensing technology, which vastly improved the efficiency of boilers.
You can read a more in-depth explanation in our "what is a condensing boiler" guide.
How Do Condensing Boilers Work?
Condensing boilers are designed to recover the heat from the waste flue gases to preheat the water entering the boiler. It’s like the unknown artist warming up the audience for a show, just with even less applause.
Condensing technology allows them to recover this heat loss by “capturing” the heat from the flue gases.
The way this works can vary and depends on the specific heat recovery system they have built into them.
For instance, some may utilise a secondary heat exchanger placed before the flue exit, or in some cases, they may optimise flow and return temperatures in the main heat exchanger to allow flue gases to hit cooler pipework and transfer energy.
This prevents energy waste and means you are getting more heat for the same amount of money. Chances are you care about money even if the environment isn’t a priority for you.
During the recovery process, the water vapour in the gasses is transformed from a vapour to a liquid, resulting in the process of condensation, hence the name. To be more technically correct, they could have gone with ‘liquidating boiler’, but that just sounds ominous.
The temperature of the flue gas can fall as much as 80°C and the heat which would have been wasted in old non-condensing models can be put to use.
During this process, as much as two litres of wastewater is generated each hour, which exits the boiler via the condensate pipe. Reusing this water makes the boiler even more efficient, nearing Iron Man levels of optimization.
Due to this heat recovery process, condensing boilers are much more efficient than old non-condensing boilers, resulting in reduced carbon emissions, energy waste and lower heating costs.
Extra add-ons can also be employed to recover even more lost heat and these are called Flue Gas Heat Recovery Systems (FGHRS), which are able to produce the same amount of heat with 7% less gas.
What is a Combi Boiler?
A combi boiler or combination boiler is the most common type of boiler installed in UK homes. It is able to provide both hot water on demand and heating water from a single unit, hence the name “combi” boiler.
Imagine if Usain Bolt was your postman, but he also did your bins... yeah, that.
Unlike system boilers and regular (heat-only) boilers, combi boilers do not require a separate hot water storage cylinder, or a separate overhead tank in the attic and all components are internal - except the hot water, which flows from your tap.
This means they do not require as much space and so are ideal for smaller properties, with some even being compact enough to fit into the average-sized kitchen cupboard.
Combi boilers heat water directly from the mains water supply, providing instant hot water on demand to taps and showers. Forget sliced bread, instant hot water is the technology everything else should be compared with.
Since they only heat the water you need, this also means that less energy is wasted, since there is no need to keep any stored and heated in its own tank.
How is a Combi Boiler, Condensing?
All modern domestic boilers including combi boilers, systems and regular boilers now use condensing technology.
All domestic boilers (and babies) produce hot waste exhaust gases, which exit the boiler via the flue, however, all new boilers are fitted with some form of condensing technology that helps to reduce heat loss and carbon emissions.
All condensing boilers are at least 90% energy efficient, making them around 40% to 50% more efficient than old non-condensing models. They can reuse the heat in flue gases, are better for the environment and will help to reduce your heating bills.
Looking for a new boiler? Get the best price on a condensing combi boiler.
Learn all about having a new combi fitted in our combi boiler installation guide.
Condensing Boiler Regulations
On the 6th of April 2018, the Department for Business, Energy and Industrial Strategy (BEIS) implemented the Boiler Plus Legislation. It was a historical day for all boiler aficionados in the UK, so the three of us went to a pub to have a drink.
The aim of this new legislation was to drastically increase the energy efficiency of residential boilers, helping to reduce carbon emissions, while decreasing heating costs. As a result, all new boilers installed in UK homes must meet these new standards.
These new standards do not just cover combi boilers either, in summary, the regulations state that:
Gas-fired boilers, both new installations and replacement, must be condensing.
Oil-fired boilers, both new installations and replacements, must be condensing.
All condensing boilers that are installed need to have an efficiency rating no lower than B.
Advantages of a Condensing Combi Boiler
Here are the main advantages of condensing boilers:
Superior energy efficiency
New condensing boilers benefit from a Flue Gas Heat Recovery System that makes them much more efficient than old non-condensing models.
This means they produce more heat from the energy used and waste less energy during the process. It’s like having a goalkeeper who can score goals, as well.
Non-condensing boilers could be less than 60% efficient and were rated as G under the ERP (Energy Related Products Directive) boiler rating system.
Reduce energy waste and your heating bill
According to the Energy Saving Trust by replacing your old G-rated non-condensing boiler with a modern A-rated condensing boiler you could save as much as £300 a year. Living without cold water saves you more, but leaves you without many friends.
Paired together with a smart thermostat and thermostatic radiator valves you could save even more.
For example, by installing a Nest, you could save up to £75 and 330kg of carbon a year, thanks to its adaptable learning schedule.
Reduce your carbon footprint
Modern A-rated condensing boilers have considerably lower carbon emissions than old non-condensing boilers.
In fact, by upgrading your old boiler for a modern condensing boiler you could save up to 1,220 kg of CO2 per year. That’s roughly the size of a pregnant walrus.
Disadvantages of a Condensing Combi Boiler
Although combi boilers are the UK’s most popular type of boiler, the reality is that they are not suitable for some homes.
Water flow rates are reduced when two or more outlets are being used at the same time. Imagine having a handful of teenagers taking showers while you need to do the dishes. Nothing would get done.
So, if you have a larger property with a few bathrooms (which may be used at the same time), a combi might not be the right choice for you.
Ultimately, a combi boiler can only heat the water which gets fed to it from the mains. So, if your mains water pressure is low, your combi boiler won't work very well. Like university students, combi boilers work best under pressure.
In summary, a combi boiler may not be suitable if:
You have high hot water demands e.g. more than one bathroom
Your mains water supply pressure is weak
Your pipework is not compatible
If a combi boiler isn’t suitable for your home, there are other types of boilers available that will be, including system and regular boilers. These are also condensing and highly efficient A-rated boilers.
Considering underfloor heating? Read our complete guide on underfloor heating with a combi boiler.
How Much Does a Condensing Combi Boiler Cost?
The cost of a new condensing combi boiler is dependent on a variety of different factors, these include the following:
The type of boiler you have installed e.g. combi, regular or system.
The boiler model you choose e.g. mid or premium range.
If you want to relocate your boiler e.g. from the garage to the attic.
If you want to convert your boiler e.g. from combi to regular.
Any add-ons you purchase e.g. filters, smart controls etc.
Check the latest prices on our combi boilers, here.
If you have Damien Hirst decorate your boiler with diamonds, the price will increase significantly.
The most common type of boiler installation and easiest is a relatively uncomplicated combi swap i.e. replacing your old combi with a new combi. For example, this is much simpler than replacing a combi with a system boiler.
What Size Condensing Combi Boiler Do You Need?
Here is a quick overview of the condensing boiler size you need:
Best small condensing combi boilers:
#1: Viessmann Vitodens 100-W 26kW
#2: Baxi 600 – 24kW / 30kW
Best large condensing combi boilers:
#1: Viessmann Vitodens 100-W 35kW
#2: Worcester CDi Classic 38kW
Best offensively large, powerful combi boilers:
#1: Worcester CDi Highflow 44kW / 55kW
#2: Viessmann 111-W 35kW
Want to know the kW you need for your home? Check out our "what size boiler do I need" guide.
Alternatively, you can use our quick boiler finder tool, which will recommend the boiler that is most suitable for your home.
If you live in an average-sized home, see our guide on choosing the best boiler for a 3 bedroom house.
Looking for the Best Deal on a New Boiler?
If so, get your new condensing combi boiler installed with Heatable, here’s why:
Get a Quote for a New Boiler Today
If you’re aiming to get the best deal on a new boiler, consider getting a quote from us, here’s why:
Gas Safe installation within 24 hours.
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Price match guarantee: We will match any like-for-like cheaper quote.
Flexible payment options, including interest-free finance.
Up to 12-year guarantee on selected boilers.
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To learn more about boilers, visit our advice section, check out our YouTube channel, or read customer testimonials here.
