Choose a boiler installer who is Gas Safe registered for boiler work, surveys your home before giving a price, sizes the boiler from your heating and hot water needs, and cleans and protects the system before the new boiler goes on the wall. They should also fit controls that meet the Boiler Plus rules, notify the job under the Building Regulations and register your manufacturer warranty, and if a quote leaves any of that out, keep looking.

Why the installer matters more than the boiler

A good boiler badly fitted will give you more trouble than an average boiler fitted well. Many early failures on newer boilers trace back to the installation: a dirty system that was never cleaned, a condensate pipe run where it freezes, a gas pipe too small for the new boiler, or a combi chosen for a house with two bathrooms and a family of five. Picking the right boiler installation company is the single biggest decision you make, and the eight checks below cover everything that matters.

1. Gas Safe registration for the right work

Under the Gas Safety (Installation and Use) Regulations 1998, only a Gas Safe registered engineer may install, service or repair a gas boiler. Every registered engineer carries a Gas Safe ID card with their photo, licence number and expiry date on the front. The back lists the categories of gas work they are qualified for, so check it covers boilers and not only, for example, cookers.

You can check a business or an individual engineer on the Gas Safe Register website before you book. Ask to see the card when the engineer arrives. It takes a few seconds and any genuine engineer will expect it.

2. A survey before the price

A proper quote starts with someone looking at your home. The survey should cover:

• where the current boiler, flue and cylinder are, and whether the new boiler can go in the same place
• the gas pipe size and run from the meter, because a new boiler can need a larger supply than the old one had
• where the condensate pipe will run, ideally inside to a waste pipe so it cannot freeze
• your mains water pressure and flow rate if a combi is being considered
• how many bathrooms you have, how many people live there and how you use hot water
• the condition of the radiators and pipework, and signs of sludge

Some installers now give an online price first, which is fine as a starting point, as long as a survey confirms it before any work is booked.

3. The right boiler type and size

Bigger is not better. An oversized boiler switches on and off in short bursts because your home cannot use its output, which wastes gas and wears parts. A good installer sizes the heating side from your home’s heat loss and the hot water side from how much you use at once.

Boiler type	Best suited to	What it needs	Watch out for
Combi	Flats and homes with one bathroom and modest hot water use	Good mains pressure and flow	Struggles when two showers run at once
System	Homes with two or more bathrooms	A hot water cylinder, no loft tanks	Needs space for the cylinder
Regular (heat only)	Older homes with loft tanks, or weak mains pressure	Cylinder plus feed and expansion tank	Takes the most space

If you are unsure which suits you, our guide to the best combi boilers explains when a combi is and is not the right choice.

4. Cleaning and protecting the system

New boilers have narrow waterways that clog quickly with the sludge and magnetite found in older systems. Building Regulations guidance expects the system to be cleaned and treated with inhibitor when a boiler is replaced, and manufacturers generally make it a condition of their warranty.

Depending on the state of the system, that means a chemical clean and flush or a full power flush. Either way, the installer should add inhibitor and fit a magnetic system filter on the return pipe to catch debris from then on. Ask which method they plan to use and why.

5. Controls that meet Boiler Plus

In England, the Boiler Plus standard has applied since 6 April 2018. A new gas boiler must have an ErP efficiency of at least 92% and be fitted with time and temperature controls. A combi boiler must also come with one extra energy saving measure from this list:

• weather compensation
• load compensation
• a smart thermostat with automation and optimisation
• flue gas heat recovery

Ask exactly which controls are included in the price. If you want app control, a smart thermostat can often satisfy the combi requirement at the same time.

6. Building Regulations and the Benchmark checklist

Replacing a boiler is notifiable building work. A Gas Safe registered installer can self-certify it, which means they notify the local authority through the Gas Safe scheme rather than you applying to building control. The Building Regulations require the notification to be made, and the compliance certificate provided to you, within 30 days of the work being completed. Keep that certificate, because a buyer’s solicitor will ask for it when you sell.

The installer should also fill in the Benchmark commissioning checklist at the back of the boiler manual. It records the settings, gas rate and flue readings on the day, and it is how installers meet the commissioning requirements in Part L of the Building Regulations. A blank Benchmark page is a warning sign.

7. Guarantees and warranty registration

There are two separate guarantees to ask about:

• The manufacturer warranty covers the boiler itself. Its length depends on the brand, the model and sometimes the installer’s status with that manufacturer. It usually has to be registered within a set time and kept valid with an annual service.
• The labour guarantee covers the installer’s own workmanship.

Ask who registers the warranty and when you will get confirmation. It should be the installer’s job, not yours.

8. What the package should include

Use this checklist when comparing quotes. If an item is missing, ask whether it is included or extra:

• the boiler, flue and any flue extensions
• controls that meet Boiler Plus
• system clean, inhibitor and a magnetic filter
• any gas pipe upgrade the survey found necessary
• condensate pipe routed and protected
• removal and disposal of the old boiler
• commissioning, the Benchmark checklist and Building Regulations notification
• warranty registration
• the first annual service, or at least a reminder when it is due

Red flags to walk away from

• no Gas Safe ID card, or a card that does not cover boilers
• a firm price given over the phone with no survey or photos
• no mention of cleaning the system
• a boiler size that simply matches the old one without explanation
• pressure to sign on the day
• vague answers about who registers the warranty

How we price it

Installations are quoted as a fixed price after a free survey, so the price you agree is the price you pay. You can get your price online in a couple of minutes with our boiler quote tool, and our other rates are on our prices page.

We are Gas Safe registered (number 956889), an Ideal Max accredited installer and a Vaillant myREWARDS installer, which means manufacturer guarantees of up to 12 years on selected Ideal boilers and up to 10 years on selected Vaillant boilers. Our new boiler packages include a magnetic system filter, the first year’s service and removal of the old boiler, and our work carries a 12 month labour guarantee.

Frequently asked questions

How long does a boiler installation take?

A like-for-like swap in the same position is usually done in a day. Changing from a regular or system boiler to a combi, or moving the boiler to a different room, typically takes two days or more because of the extra pipework and removal of tanks or a cylinder.

Should I replace my boiler before it breaks down?

If it is old, unreliable and parts are getting hard to find, planning a replacement lets you choose the timing rather than being forced into it in winter. Our guide on how long a boiler lasts covers the signs, and the repair or replace guide helps you weigh it up honestly.

How do I check if a boiler installer is Gas Safe registered?

Ask for their Gas Safe ID card and check the licence number on the Gas Safe Register website, or ask for the business registration number and look that up. Check the back of the card lists boiler work among their qualifications.

Do I need to be at home during the installation?

Someone needs to be there at the start to let the engineers in and at the end for the handover, when the engineer shows you the controls and hands over the paperwork. You will have no heating or hot water for most of the day.

Does a new boiler need servicing every year?

Yes. Most manufacturer warranties require an annual service by a Gas Safe registered engineer, and a missed service can void the warranty. Keep the service records with the boiler manual.

Boiler installation in Hertfordshire, Bedfordshire and Cambridgeshire

Our own Gas Safe engineers survey, supply and fit new boilers across Hertfordshire, Bedfordshire and Cambridgeshire from our base in Stevenage, with the system cleaned, the paperwork done and the warranty registered for you. See our boiler installation page for more, or call 01462 506374. The line is answered 24 hours a day, 7 days a week.