Combi Boiler Pros And Cons

Central heating

What Is a Combi Boiler?

Around 70% of new homes in the UK now come with a combi boiler fitted, as opposed to the more traditional boilers.

So, if your home is in need of a replacement boiler, which should you choose? What is the difference between a modern (condensing) conventional boiler and a combi boiler?

Naturally, each has its pros and cons and the choice you make will come down to the needs of your household and the demands that you plan to make of your boiler.

A combi boiler gets its name from the fact that it is a combination of a very efficient water heater, as well as a central heating unit. You may think that this exactly the same as a traditional boiler, but the key difference is that a combi boiler does it all on the fly, without need of a cylinder in which to store the hot water, or a cold water tank in the loft.

Combi Boiler Pros and Cons

The lack of a hot water storage tank is both a plus and a negative for the combi boiler. It means that crucially you save the space that a hot water cylinder takes, which is helpful in new build homes, as space is at a premium.

On the other hand you lose a handy airing cupboard and, more importantly, no hot water tank means there is no emersion heater to save the day in the event of boiler failure.

If your combi boiler fails you have no hot water until you can get somebody out to fix it.

Another consideration for the combi is the demand. If you want to take a shower you will get instant hot water at mains pressure, even without having a power shower fitted.

So that’s great, but what happens when somebody else is drawing hot water in another part of the house? The answer is that the flow of hot water may be effected.

With a combi boiler it is not possible to run more than one bath or shower simultaneously. Also, if you are about to have a new combi installed you need to get your engineer to specify a combi boiler that has the right flow rate; one that is suited to your needs.

Meaning that, although all combis take their water supply directly from the mains they are not all born equally in terms of getting that water heated and out to the consumer at a rapid rate.

In general, combi boilers are a very impressive, efficient (cheaper to run), modern, space saving system, but typically they are associated with smaller, or lower occupancy homes.

Combi Boiler Checklist – The Pros and Cons.

FeatureConventional BoilerCombi Boiler
Space RequiredNeeds space for cold and hot tanks (cylinder).No tanks needed, which saves space.
EffiencySo long as you have a modern condensing boiler it will match the combi for efficiency.Very Efficient
Cost of InstallationTwo water tanks needed. More plumbing involved.Cheaper to install.
DemandCan supply a bath and a shower simultaneously - until the stored water is all used.Only one major draw at a time
Time to Heat WaterAround 30 minutesInstant hot water at any time.
Flow of WaterHot water is taken from the hot water tank.Hot water is delivered from the mains - and delivered at mains pressure.
Improving shower flowCan fit a power showerCannot fit a power shower.
In The Event of BreakdownCan use the immersion heater for hot water, but not heating.SOS. We're cold and we have no hot water.
Ease/Cost or RepairsThe system as a whole is a bit larger, but usually not much to choose between the two.Boiler itself is a bit more cramped and fiddly to work with, but otherwise much the same.
Considerations Before PurchaseDo I have the space available. How many radiators do I need and hence what size of boiler is required.Is the mains water pressure in my area good? How many people are likely to want to bath/shower simultaneously? Do we have more than one bathroom/en suite?

How often should your gas boiler be serviced? Find out here.

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2 Comments

  • Annett flanigan

    Reply Reply 21/01/2017

    Conventional boiler allowed you to have a hot press which is really useful in a damp climate ..and cats love them

    The combi doesn’t need tanks but you do have to install a boiler and usually in the kitchen and usually on gas .. And it is ugly unless you get a cabinet constructed round it ..

    • Safeadmin

      Reply Reply 26/01/2017

      Amongst our customers opinion tends to be mixed on whether they find boilers unsightly, or not. Some want them boxed in, others are happy to let it all hang out.

      As for positioning, you can put a boiler pretty much where you want. As an example, I decided to put mine in the loft, just to safe a bit of space.

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