What a boiler service is for
A boiler service is a yearly check and clean by a Gas Safe registered engineer. It confirms the boiler is burning gas safely, catches worn parts before they fail, and keeps your manufacturer warranty valid. A typical service costs £80 to £120 and takes about an hour, checked October 2026.
It is the cheapest repair you will ever pay for. Most of the breakdowns engineers see in the first cold week of winter are on boilers that have not been looked at for two or three years.
What the engineer checks
Exact steps vary by make and model, because the engineer works from the manufacturer’s service instructions. A proper service usually includes:
- A visual check of the boiler, its casing seals, flue and pipework for damage, corrosion or signs of leaks.
- A flue gas analysis, using an analyser in the flue to measure how cleanly the boiler is burning and confirm carbon monoxide levels are safe.
- Checking the gas pressure and the rate the boiler burns gas against the manufacturer’s figures.
- Opening the casing, where the manual calls for it, to inspect and clean the burner, heat exchanger, electrodes and fan.
- Cleaning the condensate trap, which collects the acidic water a condensing boiler produces.
- Checking the system pressure and the expansion vessel charge.
- Testing the safety devices, controls and thermostat.
- Cleaning the magnetic system filter if one is fitted.
At the end you should get a written service record, and the engineer should fill in the service history in the back of your boiler manual or the manufacturer’s online log.
If the engineer is in and out in 15 minutes and never takes a flue gas reading, you have not had a service. Ask what was checked and what readings they recorded.
Why your warranty needs it
Most new boilers come with a manufacturer warranty of several years, and almost all of them carry the same condition: the boiler must be serviced every year by a Gas Safe registered engineer, with the service recorded. Miss a year and the manufacturer can refuse a free repair, even on a fault that has nothing to do with servicing.
Keep every service record together with the original installation paperwork. If you sell the house, a full service history also helps the buyer.
A service is not a landlord gas safety certificate
These two get confused all the time, and they do different jobs.
| Compare | Annual boiler service | Landlord gas safety record (CP12) |
|---|---|---|
| Who needs it | Any homeowner, and required by most warranties | Landlords, by law, every 12 months |
| What it covers | The boiler: cleaning, adjustment and safety checks | Every gas appliance, flue and the pipework in the rented home |
| What you get | A service record for your warranty | A gas safety record the tenant must be given a copy of |
| Who can do it | A Gas Safe registered engineer | A Gas Safe registered engineer |
A gas safety check confirms appliances are safe to use. It does not clean or maintain the boiler, so it will not satisfy a warranty on its own. Landlords usually ask for both on the same visit, which saves a second call-out. For the full legal duties, see the landlord gas safety guidance on gov.uk.
What a service costs
| Job | Typical price | Typical visit |
|---|---|---|
| Annual gas boiler service | £80 to £120 | about 1 hour |
| Diagnostic visit if a fault is found | £80 to £120 | about 1 hour |
Prices are typical national figures, checked October 2026. If the service turns up a worn part, the engineer should stop and give you a price before fitting anything. See boiler repair cost for typical part prices.
When to book
Book in late spring or summer if you can. Engineers have more free slots, and anything the service finds can be fixed before you need the heating. Set the date from your last service rather than from the calendar, so your warranty window never slips.
If your boiler is already showing a fault, a service is not the answer. Book a repair visit instead, and see our guides on a boiler losing pressure or a boiler not firing up for the safe checks to do first.
Who does the service
City Boiler connects you with independent local engineers who are Gas Safe registered. Before anyone opens your boiler, it takes two minutes to check they are Gas Safe registered and qualified for gas boilers. More on repairs and costs is on the boiler repair page.
Common questions
How much does a boiler service cost?
A standard annual gas boiler service typically costs £80 to £120, checked October 2026. Some engineers charge a little more if the boiler is hard to reach or needs a condensate trap or filter cleaned out.
How often should a boiler be serviced?
Once a year. Most manufacturers make an annual service by a Gas Safe registered engineer a condition of the warranty, so check your warranty terms for the exact window.
Is a boiler service the same as a gas safety certificate?
No. A landlord gas safety record (often called a CP12) is a legal safety check of every gas appliance in a rented home. A service is maintenance on the boiler itself. Landlords often book both on the same visit.
When is the best time to get a boiler serviced?
Late spring to early autumn, before the heating goes on full time. Engineers are less busy, and any fault the service finds can be fixed before you rely on the boiler through winter.
Does a service include repairs?
No. A service covers checks, cleaning and adjustments. If the engineer finds a worn part, they should tell you what it is and give you a price before replacing it.