You should normally have your boiler serviced once a year — every 12 months — by a Gas Safe registered engineer, following your appliance manufacturer’s own servicing requirements. For homeowners, an annual service isn’t a legal requirement, but it’s strongly recommended, and manufacturers commonly make it a condition of the guarantee. For landlords it’s slightly different: the law (the Gas Safety (Installation and Use) Regulations 1998) requires an annual Gas Safety Check, known as a CP12, on gas appliances — that’s a safety inspection rather than a full service, though many landlords sensibly arrange both together. Servicing yearly keeps your boiler running efficiently and gives a qualified engineer a routine chance to spot wear and developing faults early. We’re Gas Safe registered (657972) and service boilers in homes across West and North West London — you can book an annual boiler service any time.
It’s one of the most common questions we’re asked on the doorstep, usually somewhere around October when the heating goes back on. The short answer is simple — once a year — but the why, and what counts as a “service” versus a legal safety check, trips a lot of people up. Here’s the clear version.
How often should you service your boiler?
Service your boiler once every 12 months. That’s the advice from boiler manufacturers and Gas Safe registered engineers alike, and it applies whether your boiler is brand new or ten years old. A new boiler usually needs its first service within 12 months of installation for the guarantee to hold, though the exact requirement is your manufacturer’s; an older boiler doesn’t need servicing more often than annually unless it’s showing a fault, in which case you want a repair, not a service.
Is a boiler service a legal requirement?
It depends on who you are. For homeowners, no — there’s no legal duty to service your boiler, though it’s strongly recommended. For landlords, yes in effect — the law requires an annual Gas Safety Check (a CP12) on gas appliances, which is separate from a service. It pays to be precise here, because “service” and “legal check” are not the same thing.
For homeowners
There’s no law that says a homeowner must service their boiler. It’s your choice. That said, skipping it is a false economy: an unserviced boiler is less efficient, more likely to break down, and may fall outside its manufacturer’s guarantee conditions, so a failed part you might otherwise have claimed for becomes a bill you pay yourself. Check the exact terms for your model.
For landlords
Landlords have a clear legal duty. Under the Gas Safety (Installation and Use) Regulations 1998, you must arrange an annual Gas Safety Check on every gas appliance and flue in the property, carried out by a Gas Safe registered engineer, and provide the tenant with the record (a CP12, or Landlord Gas Safety Record). The HSE sets out the landlord’s responsibilities in full, including keeping records for at least two years. Importantly, this safety check is not the same as a full service — it confirms appliances are safe, while a service is deeper maintenance. Many landlords have us do both in one visit. If you let property in our area, see our Landlord Gas Safety Certificates page.
Why does an annual service matter?
A yearly service earns its place several times over. It keeps your boiler burning efficiently, so you’re not quietly wasting gas. It’s a routine safety check that can pick up a developing fault — including anything that could lead to a carbon monoxide risk — before it becomes dangerous. And it’s the point at which wear gets spotted and flagged, which gives you the chance to deal with a part on your terms rather than during a cold snap, when engineers are busiest and waits are longest.
No service can promise a boiler won’t break down. What it does is replace guesswork with a documented annual look at the appliance, by someone qualified to judge what they’re seeing.
The Energy Saving Trust makes the same point: a regularly serviced boiler runs more efficiently and safely, and a well-maintained condensing boiler holds its efficiency far better than a neglected one. That difference is small week to week, but it shows up on your gas bill across a whole winter — the service quietly pays for a chunk of itself.
Does servicing keep my guarantee valid?
It can be a condition of it, but the terms decide. Manufacturers commonly require servicing in line with their own instructions, usually documented annually, for a guarantee to stay valid — and the guarantee length itself varies widely by brand, model and installer scheme. Miss a year and you may find a claim refused on a part that would otherwise have been covered. Check the exact current terms in your own boiler’s guarantee documents rather than relying on a general rule. We keep a digital service record for every boiler we look after, so your history is there in black and white, and on new installs we register the guarantee for you so it’s sorted from day one.
One detail catches new-boiler owners out: manufacturers often want that first service done within 12 months of the installation date, rather than at some looser point in the boiler’s first year — leave it too late and the guarantee can lapse on a boiler that’s barely been used. Again, the exact requirement is in your own paperwork. If we fitted yours, we log the install date and remind you when it’s due, so the cover holds when you actually need it.
What happens during a boiler service?
A service is carried out to the specific appliance manufacturer’s instructions, so the exact checklist varies by make and model rather than following one universal routine. Broadly, a Gas Safe engineer confirms the boiler is operating safely and efficiently: inspecting the main components and controls, checking gas pressure and flow, testing the flue for safe emissions, looking for leaks or corrosion, and confirming system pressure is correct. We’ll clean what the manufacturer’s schedule calls for, flag anything starting to wear, and leave you with a clear record of the boiler’s health, plus honest advice on anything worth keeping an eye on. No upselling, ever.
If you want to know exactly what’s included at each level, we set our two packages out plainly in standard vs full boiler service.
What about sludge and system water?
Worth understanding, because it’s often misunderstood. Sludge is the black magnetite that builds up as a sealed heating system slowly corrodes from the inside, and it’s an important cause of circulation and component problems: it can jam a circulating pump or diverter valve and restrict the heat exchanger. The defences against it are a correctly dosed corrosion inhibitor and a magnetic filter on the heating circuit.
What’s important to be clear about is exactly where the line sits, because it’s often drawn in the wrong place. We check the system water and the magnetic filter on both of our service types — a filter loading up quickly tells you something a visual inspection never will. What a standard appliance service doesn’t automatically include is testing or topping up the corrosion inhibitor: a service follows the boiler manufacturer’s schedule, and inhibitor work sits outside it. If what we find points that way — repeated breakdowns, cold spots, a heavily loaded filter — we’ll say so and explain what testing involves, rather than assuming.
Limescale is a different problem again, on the fresh-hot-water side rather than the sealed heating circuit, and it’s worth keeping the two apart. That’s a bigger topic for homes across Ealing, Chiswick and the rest of West London — we cover it in hard water and your boiler.
When’s the best time to book a boiler service?
Late summer or early autumn — ideally September or October, before you rely on the heating every day. Two reasons. First, if the service turns up a fault, you’d far rather find it on a mild September morning than during the first cold snap, when you’ve no heating and every engineer is flat out. Second, that January rush means longer waits, so booking ahead gets you a slot that suits you. A boiler serviced in the autumn heads into winter as reliable as it can be — which is the whole point of doing it.
How much does a boiler service cost?
Across the UK, a one-off gas boiler service typically costs £80–£120, averaging about £100, in 2026 (national market figures for budgeting, per Checkatrade’s March 2026 cost data, with London tending to sit toward the upper end). These are general market figures, not a quote — for our price and to book in, see our boiler servicing page, or ask us about a care plan that spreads the cost and keeps you on track each year.
Frequently asked questions
How often should you service your boiler?
Normally once a year, every 12 months, by a Gas Safe registered engineer, following your appliance manufacturer’s own servicing requirements. It’s recommended for homeowners and commonly a condition of the guarantee. New boilers usually need their first service within 12 months of the installation date.
Is a boiler service a legal requirement, and how does it differ from a CP12?
Not for homeowners. Landlords must arrange an annual Gas Safety Check under the Gas Safety (Installation and Use) Regulations 1998, recorded on a CP12: a legal safety inspection of the gas appliances and flues they provide. A service is different — deeper maintenance to the manufacturer’s instructions, commonly a condition of the guarantee. Landlords often book both together.
Does servicing keep my boiler guarantee valid?
It’s commonly a condition of it, but the exact terms decide. Manufacturers generally require servicing in line with their own instructions, documented, for the guarantee to hold. Check your own boiler’s guarantee documents. We keep a digital service record for every boiler we maintain, so the history is easy to prove.
How long does a boiler service take?
In our own experience across West London, a standard service on a boiler in good condition is typically a 30-to-60-minute appointment. It varies by make and model, because the work follows that manufacturer’s schedule. Allow longer if the engineer finds a fault worth investigating, or a part that needs attention.
How much does a boiler service cost?
A one-off gas boiler service typically costs £80–£120 across the UK in 2026, averaging about £100 (Checkatrade, March 2026), with London tending to sit toward the upper end. These are national market figures for budgeting, not a quote — see our boiler servicing page for our price.
When is the best time of year to service my boiler?
Late summer or early autumn, ideally September or October, before you depend on the heating daily. Any fault turns up while the weather’s still mild, and you avoid the January rush when waits are longest. A boiler serviced in autumn heads into winter as reliable as it can be.
Does a new boiler need a service in its first year?
Usually yes. Manufacturers commonly require the first service within 12 months of the installation date for the guarantee to hold, so even a nearly-new boiler needs booking in. Check your own paperwork for the exact requirement. If we fitted yours, we log the install date and remind you.
Book your annual boiler service in West London
Due a service, or not sure when your boiler was last looked at? It takes 60 seconds to get booked in.
- WhatsApp us — Book in 60 seconds
- Call 020 8051 2124 — our line is answered 24/7 and we’ll get your details to an engineer
- Book online: boiler servicing
We’re Gas Safe registered (657972) and keep boilers healthy across West and North West London — from Ealing and Chiswick to Kilburn, Queen’s Park and beyond. Heating that just works, no drama.
About the author Adam Said is a Gas Safe registered domestic gas engineer (657972) at The Happy Heating Co, servicing, installing and repairing boilers in homes across West and North West London. This guide reflects what we see on real jobs every week.
Related reading
- Boiler servicing in West London
- Landlord Gas Safety Certificates (CP12)
- Boiler repairs
- How much does a new boiler cost in West London?
- Hard water in West London: what limescale does to your boiler
- Areas we cover
Cost figures are typical UK market averages from Checkatrade’s March 2026 boiler service cost data, for budgeting only — not a quote. Servicing guidance reflects Energy Saving Trust advice; landlord duties are set out in the Gas Safety (Installation and Use) Regulations 1998, enforced by the HSE. Guarantee conditions vary by manufacturer, model and installer scheme; check the exact current terms for your own boiler.
