If you’re looking for a new combi boiler but don’t know which one to choose, try our new Boiler Selector Tool. Simply work your way through the questions and select “combi boiler” from the options when you reach the “What type of boiler do you require?” question. But what do all these options mean, and how do they influence your choice of combi boiler? Here, we’ll take a look at all the factors that determine the best combi boiler for you.


Before you opt for a combi boiler, make sure you satisfy the following factors:

  1. You live in an area with normal or high water pressure
  2. You don’t often need to use several hot water appliances (sink, bath, shower) simultaneously
  3. The boiler is going to be relatively close to the furthest bath, shower or sink (less than 20 metres)

Property type


First, you’re asked to decide between detached house, semi-detached house, terraced house, bungalow and flat

Why we ask

The smaller the property, the less powerful your boiler needs to be. Although the boiler uses mains pressure to deliver hot water, you may still notice a drop-off in pressure if your boiler is too small for the home, and the longer the pipework between the boiler and the tap, the longer you’ll have to wait for the hot water to emerge when you turn it on.

How many bedrooms do you have?


We now ask how many bedrooms you have: 1, 2, 3, or 4 or more

Why we ask

This will give us two indications: what will be the demand placed on the central heating system, and roughly how many people live in the home. Both of these factors feed into the calculation, as they determine the power your boiler will need, especially if you have a large family, when it’s more likely there will be simultaneous hot water demands.

How many bathtubs do you have?


We ask whether you have 1, 2 or 3 or more baths.

Why we ask

Although most households get by with just one bath (usually with showers in addition), if you’ve got two, it’s probably because you need two, and that can only really mean you use them at the same time. Two baths running simultaneously would be asking a lot of a small combi boiler, and even a larger one would struggle. It’s possible that a system boiler or conventional boiler would suit you better in this case.

If you bought the house and it happens to have two baths, but you hardly ever use them, or would never use both at the same time, select “1 bath”.

How many showers do you have?


How many self-contained showers do you have: 1, 2, or 3 or more. If you have a shower that runs direct from your bath-tap mixer, that doesn’t count as a shower for the purposes of this question. If you have an electric shower, ignore it – it has nothing to do with the boiler. 

Why we ask

We need to know how many self-contained shower units you have that run from the boiler. Like baths, if you have several running simultaneously, it will put a demand on the boiler, and you could find the water comes out at lower pressure and temperature than you would like.

Again, if you have a house with several shower units but only ever use one at a time, select 1.

What type of boiler do you require?


Here, you’re asked if you’d like a combi, system or heat only boiler.

Why we ask

The different types of boiler all come with their pros and cons. The main pros of the combi boiler are that they provide instant hot water and they don’t heat water unnecessarily. Larger households with multiple occupants would often be better off with a system or heat only boiler setup, as they can deliver hot water to multiple taps at the same time.

However, for this article, we’ve assumed you’ve opted for the combi boiler.

What kind of fuel does your boiler use?


There are two options: Natural gas and LPG (bottled gas).

Why we ask

The majority of households in the UK use natural gas, i.e. mains gas. However, some isolated buildings are not connected to the gas network, and will therefore require gas to be delivered in LPG (liquid petroleum gas) bottles. This fact might influence the type of boiler you can use.

We'd suggest the following boilers for you


You’ll now be given various options based on the facts and figures you’ve given us.

Why we ask

These are the combi boilers that will cope best, considering the information you’ve given us. Although you’ll be given some basic information at this stage (the duration of the warranty, its efficiency rating and what the unit looks like), we’d urge you to look deeper into the specifications before you make your choice. Ideally, this guide will give you a ball-park idea of the kind of boiler you’ll need and how much it will cost, but you should ask a professional installer to confirm your choice, as they’ll know if you’ve chosen the most appropriate one.

Controls and Accessories


Finally, you’ll be offered a range of controls and accessories. These options will depend on the boiler you’ve chosen, but typically they’ll let you choose between different types of timer, manual connection thermostat and mobile-connected devices. You can select more than one accessory here.

Why we ask

The control is a crucial part of your central heating system, and will instruct the boiler to fire up to get your home warm. At its simplest, it’s just a thermostat that detects room temperature and turns on and off if it’s colder or hotter than your chosen setting.

Modern systems are connected to the internet via your Wi-Fi, and you can turn the heating on and off wherever you are – handy if you’re about to set off for home from work on a wintry day, but don’t want the heating to be on all day long.

Ultimately, it’s your choice. The simpler solutions cost less, but the modern ones give you more flexibility.

Please get in touch if you need help

If you need advice choosing your combi boiler, please get in touch – we’ll be glad to help.

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