Call for free advice & quotes

What's the difference between a System, Regular or Combi Boiler?

Get in touch
or call us now 0203 370 0066

Boiler InstallationThe difference between boiler systems can be confusing for new property owners who never have had to deal with such things before. There is often the question to switch older properties with traditional heating systems to a new combi boiler installation - but doing so can be expensive.

This guide is aimed at giving you a comprehensive look at the main types of boiler system available for domestic properties, and what extra expenses might arise when installing a new system.

Firstly, let's break down the main types of boiler installation:

The difference between the three main types are in the storage of the hot water. Let's start by explaining a Combi boiler system.

What is a Combi Boiler?

A combination boiler, or 'combi boiler' for short, handles both hot water and central heating. Most modern installations now use combination boilers as they're the most efficient and cheapest to run.

The advantage of a combi boiler is that it only heats the water when you need it, so you're not using excess gas.

A combi boiler works straight off the cold water mains, heating the water almost nearly instatenously via a super-efficient internal heat exchanger. This also means that the hot water will be delivered at mains pressure - often reducing the need for a shower pump.

Combi Boiler

There is a slight disadvantage as the hot water won't be quite as quick to come through as it will on a regular or system boiler, but you will save money on your fuel bills.

A combi boiler system doesn't require a hot water storage tank of any kind as the central heating water simply circulates throughout the system and the hot water gets delivered straight from the mains.

Keep in mind that for a combi boiler to work properly, you need a decent mains pressure. If your area lacks this then opting for a System or Regular boiler installation would possibly be better. 

What is a System boiler?

A System boiler requires a separate hot water tank, but no expansion vessle - and a lot of the components are built inside the boiler, making installation easier than a regular system.

The hot water tank should ideally be stored within an airing cupboard - this will usually be an unvented hot water cylinder. There is no requirement for a tank in the loft, so you'll increase the free space you have up there.

System boilers are best suited for larger properties where the demand exceeds what a sigular combi boiler can manage. A big advantage is that it can support multiple outlets running hot water at once, without comprimising the heat from any one outlet.

Having the sealed tank ensures a constant pressure in the system and a very short wait until the hot water comes through the taps. However, as the water is stored in a hot water cylinder - there is the risk of the tank running out if demand gets too high.

What is a Regular Boiler?

A Regular boiler is designed to fit into a traditional style central heating system, which consists of two water tanks and a hot water cylinder.

Most older properties will have regular systems installed already, so when upgrading your regular boiler you might only need to swap the boiler itself.

Even though there are more elements to a regular system, installation is still quite simple and the boilers themselves are still as energy efficient as a System equivalent.

Most of the central heating system's components are stored in the loft, with the hot water tank often being stored in an airing cupboard. The two tanks in the loft are the water cistern, which feeds cold water into the heating system and the expansion vessle, which protects the central heating system from excess pressure.

So what hot water boiler
is best for your home?

It largely depends on what you already have installed and what your property's hot water demand will be.

If you already have the components needed for a Regular system, and you don't require the free space in your loft, then it's probably worth having a new regular boiler installed.

If, however, you want to free up some space in your loft and opt for a more compact central heating system. Then a System boiler with a sealed hot water cylinder might be best.

As a large amount of pre-heated hot water is stored in a tank, these are both good choices if the hot water demand in your property is high. So for example, if you think two showers might be in use at the same time then opting for a system with a hot water tank would be best to cope with the demand.

On the otherhand, Combi boilers are the most popular choice. They use the least space and are the cheapest to run. No hot water cylinder is required and the water is heated on demand.

How do I choose a boiler brand?

A question we get asked a lot is how you can make the right decision as to what brand of boiler is best for your property.

The easiest way to answer this is to look at your budget, the output you need and whether you require any other separate controls.

Key manufacturers for average priced good boilers are Vaillant, Worcester-Bosch, Baxi, Glow-Worm, Potterton and Viessmann. The main two choices of our engineers are the Vaillant ecoTEC range and Worcester-Bosch's Greenstar range as these are both reliable, economic and asepthetically pleasing boilers.