CALL: 07859 896019 →

Combi Boiler vs Conventional

combi boiler install

Many people will not understand the difference between a combi boiler and a conventional boiler. When we visit clients looking for a new boiler installations, we will always recommend a combi boiler over a conventional. Of course, we would only recommend it when it is suitable as there are limitations.

Combi boilers have become increasingly popular over the last few years due to the rise in new builds and multiple government schemes such as the Governments “ECO Scheme“. This scheme in particular will allow homeowners or private tenants the ability to have their old boilers replaced for free or at a heavily discounted rate.

The average person is not meant to understand the “ins and outs” of boilers but it is important to know the difference. You may have a pushy sales person try and sell you a boiler, which is the complete opposite to what you actually require. Below is a complete guide into the world of domestic boilers.

What is a Combi Boiler?

A Combi Boiler is short for Combination Boiler and it is the combination of a water heater and central heating boiler system that is inside a single unit. When running a hot tap, it will get the heated water straight from the mains and not any storage water tanks.

Compared against the conventional boiler system, it takes up much less space and is more cost effective as water is heated instantly as opposed to being heated and stored. Below are the Pros and Cons of installing a Combi Boiler:

Pros of Combi Boilers

  • No need for loft space for water storage tanks
  • More energy efficient
  • Compact size
  • Less pipework required
  • Suitable for new build properties

Cons of Combi Boilers

  • Mains water pressure needs to be good
  • No backup immersion heater
  • Cannot run multiple hot taps at once
  • Power of the shower is dependent on water pressure

One of the main reasons people choose to install a combi boiler is due to the fact you can get rid of the storage tanks. For smaller houses or flat, this can make a big difference and can make way for additional storage space. Our team of plumbers in Cardiff are installing combi boilers at a much greater rate than the older conventional boilers.

conventional boiler replaced

What is a Conventional Boiler?

Older homes or large properties often prefer a conventional boiler (also known as a traditional or regular boiler) over the newer combi boilers. They use a heating and hot water system with two water tanks, which one is storing hot water and the other is cold water.

The conventional boilers are usually stored in the loft and unlike the combi boilers, it does not require a high water pressure to function correctly. Below are some of the Pros and Cons of a conventional boiler:

Pros of Conventional Boilers

  • Large or multiple occupant buildings will have instant hot water
  • Hot water served better to multiple bathrooms
  • No water pressure requirements
  • Possibility to combine with solar energy

Cons of Conventional Boilers

  • Large amount of storage space required for tanks
  • Not energy efficient
  • Limit to the amount of hot water available
  • Water pump is separate to the heating systems (even more space needed)


Adding a combi boiler to your house will almost certainly add value to your property but it does require a large upfront cost for the boiler itself and installation. Larger properties or multiple occupant buildings should stick to a conventional boiler due to the fact running multiple hot taps at the same time can be problematic. If you are looking to improve the efficiency, we would recommend improving the insulation around the water tanks in order to maintain the heat and stop it escaping.

© N.J Harkus Plumbing and Heating Ltd
180 Ffordd James McGhan, Cardiff, CF11 7JU
Website and SEO by WebSpection