Your step-by-step guide to boiler installation

From finding the right size and type of boiler for your home to having it installed on your wall, here’s everything you need to know about boiler installation.

Finding your perfect boiler

We know that installing a new boiler can be a big, and often stressful, decision. But it doesn’t need to be. With our handy boiler calculator all you need to do is answer a few questions about your home and heating system, and we’ll work out which is the best boiler for you. And we’ve also got a simple boiler installation guide right here to help you make sense of it all, so you’re prepared for boiler installation day.

Understanding the types of boilers

There are three basic types – the combi, the conventional and the system boiler. Before you arrange a boiler fitting, you want to make sure you’re getting the right one. Our dedicated guide to the types of boilers will help with that, giving you more information about each boiler type, how it works and if it’s right for your home.


Generally, when you get a new boiler installed, you’ll probably want to go for the same type as it makes installation easier. However, switching to a new, energy efficient boiler will outweigh the disruption if you do need to change boiler type.

What’s the best boiler size for you?

It’s always good to ask your gas engineer to get the best answer for this. But there are a few considerations when preparing for a new boiler fitting.

How much water do you use?

If you live in a large family home, you’re likely to use more water than a single occupant in a one-bedroom flat. Generally speaking, conventional boilers are better suited to meet higher water demands, and combi boilers are best for lower usage.

How much space do you have?

No space in the loft for a tank? Airing cupboards filled to the brim with towels? Then combi boilers are a good option as they don’t require a hot water cylinder.

Where do you want your new boiler installed?

For easy installation and minimal disruption to you, it’s best to get a new boiler installed in the same place as the old one. Most people tend to go for kitchens or cupboards, but you can place it in almost any room, as long as it has the correct pipework and the flue can be positioned correctly.

Can someone give you no-nonsense information?

You bet. Us! We’ll help you find a new boiler and give you a free quote on the best one for your home. While you’re there, you can also make an appointment to talk to one of our heating advisors. They’re here to give you any help and advice you need – just get in touch.

Finding a safe boiler installer

You’ve got your quote, you’ve identified which boiler you want to go for, now you just need a trusted engineer to install it. All our engineers are Gas Safe registered, and you should never use one who isn’t. We’ve created a comprehensive guide to finding a trusted gas engineer, which will give you all the information you need to choose wisely.

When’s the best time to get a new boiler installed?

When you need a new boiler, you need a new boiler. There’s not always a right time. But if you’re planning on replacing yours before it completely packs up, then we’d recommend doing it during the summer months. That way you’ll be less reliant on heating and hot water so the process should be relatively pain free. Imagine a boiler fitting in the cold winter months…

What happens during boiler installation

What good would a boiler installation guide be without letting you know what actually happens beforehand, on the day, and after a boiler fitting. Any good gas engineer (and ours are excellent by the way) will try to make the process as simple as possible. They’ll cover carpets, surfaces, bring the right materials with them and start working safely and efficiently, while adhering to all legislation. Doing the job right means they’ll leave no trace of their visit, except maybe a few biscuit crumbs if you decide to spoil them.

1. Before work begins

Your Gas Safe engineer will check a few things with you first. Such as how many radiators you have, your water pressure, the number of bathrooms in your home and the positioning of the current boiler and flue.

2. On the day

If it’s a straightforward swap — e.g. combi for combi — you should expect the engineer to be done and dusted within the day. It’s worth bearing in mind though that if it’s a much older boiler system or you’re changing boiler type, there may be complications which prolong the installation. You’ll need to be around to have a run-through of the new boiler controls once it’s fitted.

3. How much will it cost?

Boiler installations aren’t always cheap. They depend on whether it’s a basic like-for-like switch to a newer model, or a complete system change, with Powerflushes and additional pipework. Make sure you get a quote upfront to avoid any nasty surprises. And don’t forget, you can always get a free quote from us to help you begin your new boiler journey.

4. Getting the right documentation

To comply with Building Regulations and Gas Safe rules, all Gas Safe businesses need to notify the local authorities whenever they install a new gas appliance. And they should give you a Building Regulations Certificate, as well as a completed Benchmark Certificate, to prove compliance. Be sure to query this if it doesn’t happen.

5. What happens after installation?

Most reputable companies will offer you a guarantee on their services, and here at British Gas, we offer up to 12 years’ warranty on our installations. These terms may vary from business to business, so always check before agreeing to the work.

If you’re concerned about the safety of your new boiler installation, or think that your engineer has done a bad job, follow up with them right away. They’re obliged to put right any problems they’ve created, or reimburse you for the cost of hiring a new engineer. If you’ve hired a Gas Safe engineer, you really shouldn’t have to worry.

And that’s it in a nutshell! Hopefully you feel a bit more clued up on your boiler installation now, but if you still have any questions, our heating advisers are on hand to help. And, for more information around British Gas boiler services, visit us here.

Find your perfect boiler