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Witten by Bernard Morgan (Engineer) & Adam Apperley (Marketing). Published: October 27, 2023. Updated: February 1, 2024

A Simple Guide to Gas Boiler Installation

Introduction and Contents

In this guide we’re going to look at a number of factors surrounding gas boiler installation. This will include which type of boiler system is best for you, which boilers will suit you, who to get to install it and where, plus a load of frequently asked questions on the subject.

A bit of a cop-out, but it all depends on your own situation. Most homes in the UK either have a combi boiler or a system boiler. However, technically anything is possible with enough money. At Boilerhut we try to give you the best suited boiler and set-up for your home. We’ll obviously discuss everything with you to ensure that we fully understand the needs of your home or property to give you the best options.

Types Of Gas Boilers And Heating Systems

Before we get into what’s right for you we’ll assume you don’t know anything about boilers or heating systems, which means we shouldn’t miss anything, and you can skip bits you already know.

The main type of boilers in the UK are:

  • Combi Boilers

    combi boilerThe most popular type of boiler in the UK. They power your radiators and heat hot water on demand, so you don’t need a separate hot water storage tank. Combi boilers are compact and easy to install, and they are suitable for most homes.

  • Large Storage Combi Boilers

    Storage combi boilers are, well,  combi boilers with in-built hot water cylinders that can help provide a lot of hot water without the need for further cylinder installations.

  • System Boilers

    full system set upSystem boilers produce hot water which is diverted to radiators or your hot water cylinder or both. This system is not designed to produce instant hot water like a combi. These system boilers are more suitable for larger homes, especially with multiple bathrooms.

  • Regular boilers

    regular boilerRegular boilers, generally, have the same set-up as system boilers. The difference is that they’re not pressurised and are ‘open vent’ and gravity fill from a tank in the loft.

  • Air Source Heat Pumps

    This guide isn’t focusing on the air source heat pumps. We’ll have more information about them very shortly.

Combi boilers have become so popular in the last few years because, in general, they are simpler to install and maintain because everything is in the one box. They’re also highly efficient as you don’t end up with large amounts of hot water available at all times.

Fueling Your Heating

Let’s quickly consider fueling your heating system. Most properties in the UK have a mains gas connection. This means that the gas is delivered directly to your door, fantastic. Unfortunately, a lot of homes are not connected to the mains and so need an independent source of fuel.

These sources are normally electric, LPG or oil.

all fuels - gas oil lpg electricity

With oil a large double-skinned, or bunded, fuel tank which will sit somewhere in your garden and cost approximately £1,200 – £2,200 to install. You get these filled up by local suppliers. The industry is working on bio-oils and the boilers we provide are biofuel-ready.

LPG, or liquid petroleum gas, is supplied in either bottle form (think large BBQ gas bottles) or in bulk. If you want bulk deliveries you will need a large pressurised on your property. These could be buried underground if you don’t want them visible.

Most boilers can either do a combination of fuels (gas or LPG) and have specific models for oil.

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Running Costs

Boilers don’t run for free. We all know this. The advice we give here at Boilerhut is get the best system for you. It’s personal and depends on a number of factors…too many to go through even in an ‘ultimate guide’. But you will need to consider; number of bathrooms/hot taps and showers, how many radiators you have and your cold water flow rate.

With these considerations we will be able to talk you through a system that is right for you. One thing to remember is that you don’t want a boiler that is too powerful. It will cost you more money to run for no reason. If we advise you only need a 15kW boiler, a 30kW boiler isn’t going to do anything twice as quickly or as well. It will cost you more money to run to have the same output.

When considering costs, the best and most important thing to look at is efficiency. We work with Viessmann who produces a boiler that is 98% efficient! This means that for every £1 you put in, you get 98p of heating and hot water and only 2p is lost through heat-loss.

Plus, as Viessmann uses stainless steel heat exchangers the efficiency doesn’t reduce over time like with an aluminium exchanger, saving you money, for longer.

Sometimes it is 100% worth speaking to someone to go through this with you. So why not get a quote below and let us call you back for a quick and free, no-obligation quote.

Viessman’s Inox-Radial Stainless Steel Heat Exchanger

Below: One of the most important features in a Viessmann boiler is its patented heat exchanger.
Right/Below: Data showing stainless steel heat exchangers (blue) compared to aluminium (red).

viessmann's inox radial stainless steel heat exchanger

viessmann boilers stainless steel heat exchanger vs aluminium exchangers

Which boiler is best?

Viessmann Vitodens 100-W

Boiler: Viessmann Vitodens 100-W

As discussed, here at Boilerhut we’re premium installers of Viessmann boilers. We work closely with Viessmann. This allows us to offer up to 12 year warranties and use their own technicians to service their boilers every year to ensure it remains in warranty for the full term.

However, Viessmann aren’t the only boiler manufacturers we work with. We have close relationships with Alpha, Navien and multiple others. It all depends on your fuel-type and specific needs.

If you would like to read more about which boilers we think are the best, please read this guide on the best boilers >

In general if you have mains gas or LPG we will almost always suggest a Viessmann Vitodens boiler, the models are the 050-W, the 100-W, 111-W and the 200-W. With oil, we normally recommend Navien boilers. Although we’re not detailing this in this guide, any air source heat pumps we supply are either Alpha E-Tec Hybrid systems, or the Viessmann Vitocal range.

Ideas Of Cost

As a quick summary, The average combi boiler replacement cost is between £1,600 to £3,500. inc. VAT with Boilerhut.

Boilers can range from £850 to over £5,000 (for the biggest and best ones). Then you will need to add on labour and any additions like a system flush, magnet filter, hard-water filter, any new pipes that need to be added or upgraded due to install location and regulation upgrades (gas pipes need to be 22mm in diameter and some older properties have smaller pipes).

If you would like a more detailed breakdown of the costs involved read this article >

Other Additions To The System

There are other additions to the boiler set-up that you can look at as well:

  • Smart controllers, such as Tado or Nest,
  • New or replacement radiators in the property,
  • Will you need a new or replacement flue to meet building regulations?
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Where Should I Put The Boiler In My Property

The location of the boiler will come down to a few details about your home, plus where you would actually like it.

Considerations include:

  • Is there already a boiler in the property that you are replacing/upgrading?
  • Where are all your radiators’ pipes feeding to?
  • Where does the gas pipe come into the property and where is your gas meter?
  • Do you have a soil-pipe or access to the outside for the condensate pipe?
  • Although Viessmann boilers are very quiet, would you like it somewhere away from ‘normal’ living space (the garage, utility room etc)?
  • Where are your bathrooms in the property can also help decide your boiler location due to pipe work.

Who Should Maintain It

At Boilerhut we work closely with the manufacturers of the boilers we install. In the case of Viessmann, in order to maintain your 10 or 12 year warranty (model dependant), we can offer either an annual service, where we’ll contact you each year to remind you, take payment and book you in. Or we now offer a monthly plan which will give you the service plus access to an out of hours support line.

Obviously, you don’t have to use us for the annual servicing, but any boiler installed will need a manufacturer approved annual service to maintain the warranty.

We have had a couple of customers recently contact us 4 or 5 years after installation saying their boiler has stopped working. But because Viessmann haven’t been out to service it, the warranty may become void and liability will no longer fall to Boilerhut or Viessmann. We will do what we can to try and look after everyone, but the boilers must be looked after to maintain them well.

First Steps

Obviously there are a lot of things to think about when looking at installing a boiler into a new property, replacing one type with another, or replacing a broken-down boiler with a similar set-up.

The easiest way to get a quote from us is to start with the online quoting system. It will ask you a few questions to get an idea of what you need and then provide a fixed quote based on your answers. We’ll then contact you to ensure we have all the correct details for a full and final quote.

Start a no-obligation quote now >

Once we’re happy with the information we have, and you are happy with the quote, we can often install boilers within just a couple of days…sometimes within 24 hours – even on weekends.

If you have so many questions the quote engine doesn’t seem right for your setup call us on 029 2009 9898 and speak to one of our amazing sales engineers.

In terms of payment we can take most major credit cards (not AMEX) and we offer financing through a partner. We can either reserve the full amount on a card or take a deposit for the gas boiler installation. Full payment will be taken after the installation and once you have signed off on the installation.

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  • How quickly can you install the boiler?

    Once we’ve taken a deposit, reserved payment or your financing has been agreed we start looking at our installers schedules. The average time to install a boiler is less than a week with some boilers being fitted the same day.

  • Do you install boilers near me?

    We install all over the UK, excluding Northern Ireland at this stage. We have a network of great Gas-Safe engineers that are based all over England, Wales and Scotland.

  • Where are you based?

    Our head-office is just outside Cardiff. But we’re a true, UK-wide business.

  • Do you have a service plan?

    We can currently offer a service plan for any gas Viessmann boilers. We’re an authorised Viessmann partner which means we’re able to offer up to 12 year warranties (depending on model) as the plan guarantees Viessmann will service the boiler themselves.

  • Do I need to service though you?

    No, not at all. However, to keep the warranty valid for the 10 or 12 years you will need to ensure that the 12-point manufacturer service plan is followed. Boilerhut only uses Viessmann engineers, so they’re looking after their own units meaning they will do everything correctly.

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