What your installer should include in a quote
Check your installer has named the boiler's efficiency, the controls and the notification route.
See what to check →When you need a new boiler
You probably don't replace a boiler very often. It may be years since you last did it, or this may be the first time.
You want it done well. You also want to pay a fair price for it. For most of us, it's hard to tell what a fair price is, because we don't do this kind of work ourselves. When the work is done, you'll want the paperwork too. You may need it one day if you sell your home.
We wrote this site to help. We explain what your installer has to do, and what you can talk through with them before you agree.
How efficient does the new boiler have to be?
Under Approved Document L, a gas boiler replacing one in an existing home needs to reach at least 92% efficiency, the same number used under the ErP rules. Ask your installer to write that efficiency figure into the quote next to the boiler model. We explain how to read that number against the one on your quote in our guide to efficiency figures.
What should your installer put in the quote?
When your installer puts the quote in writing, you can see what you're agreeing to before anyone starts work. That includes the boiler going in, and how your installer plans to sign the job off. Ask for it in writing. We go through what your installer should include in a quote, line by line, in our guide to boiler installation quotes.
What paperwork should you get afterwards?
Once your installer finishes the job, they have 30 days to give you a copy of the compliance certificate and tell building control the work is done. Ask your installer when to expect that certificate, and chase it if it hasn't arrived. We explain who sends what, and what to do if nothing turns up, in our guide to notification and paperwork.
Ask your installer to register the boiler with its manufacturer too. With one manufacturer, Ideal Heating, you register it within 30 days of installation to get the full warranty.
Three things to look at first
If you have a quote in front of you, these three points will tell you most of what you need to know.
Where the flue can go
A gas boiler's flue has a position your installer works out from the manufacturer's instructions and Approved Document J.
Read about flue position →The certificate you should get
Within 30 days of finishing, your installer should give you a copy of the compliance certificate and tell building control.
Find out who notifies whom →Which rules apply to your boiler right now
Right now, the 2021 edition of Approved Document L governs a gas or oil boiler replacement, with its 2023 amendments folded in. The next edition takes effect on 24 March 2027, so unless your job sits right on that date, the installer quoting your work should be pricing and specifying against the rules as they stand today.
Does the date change anything on your quote?
For most people getting a boiler replaced this year or next, no. The new edition only starts to matter if your installation is notified to building control close to that March 2027 date, or if work is delayed well past when it was first agreed.
If your installer notifies the job to building control before 24 March 2027 and the work itself starts before 24 March 2028, it stays under the rules that apply now, even after the newer edition is in force (Circular 01/2026). If timing like that applies to your job, ask your installer which edition they are working to and when they notified building control.
What should you check on a boiler quote?
Before you sign a quote, go through it with your installer and check these five things. A clear answer to each one tells you what kind of job you're agreeing to.
Is your installer Gas Safe registered?
Ask to see your installer's Gas Safe registration card, or check the register yourself at gassaferegister.co.uk before you agree to anything. You can read on the card which types of gas work your installer is registered to do.
Has your installer included an efficiency figure of at least 92%?
For a gas boiler, ask your installer to write down that number and check it's at least 92%. That's the minimum for a gas boiler in Approved Document L. We explain how to read that number in our guide to efficiency figures.
Has your installer named the controls?
Ask your installer to name the thermostat, the programmer and the thermostatic radiator valves they're fitting, and where each one is going. You can ask for the make and model of each one in writing.
Will your installer clean and protect the system before fitting the new boiler?
Ask whether they'll flush the existing pipework and radiators before fitting the new boiler, and whether they'll add an inhibitor afterwards to protect it.
When will you get your certificate?
Ask your installer when they'll send your certificate, and check you receive it within 30 days of the job finishing. We explain who sends it and what to ask for if it doesn't arrive in our guide to who notifies building control. We've put the full list in our quote checklist. You can hold it up against the quote in front of you.