Central heating — London
Central heating installation and repairs in London
Gas Safe registered engineers installing, repairing, upgrading and servicing central heating systems across London — boilers, radiators, pipework, cylinders and smart controls. Free survey with a proper heat-loss assessment, fixed-price quotation, and same-week callouts. All 33 London boroughs covered.
£2,000–£9,500
Typical London central heating cost range, 2025
92%+
ErP efficiency rating required for new gas boilers (Boiler Plus)
8–14
Radiators in a typical 3-bed London terraced house
1–5 days
Installation time from boiler swap to full new system
The basics
What a central heating system is
A wet central heating system — the standard setup in the vast majority of London homes — circulates hot water from a boiler through a network of pipework to radiators in every room, before returning to the boiler to be reheated. The same boiler usually also provides hot water for taps and showers, either instantly (combi) or via a stored hot water cylinder (system and regular boilers).
A combi (combination) boiler heats water directly from the mains on demand, with no cylinder or cold water tank required — the most common choice in London flats and smaller houses because of its compact footprint. A system boiler works with a hot water cylinder, usually an unvented cylinder pressurised from the mains, and suits larger properties or homes with two or more bathrooms where several outlets may draw hot water at once. A regular, or heat-only, boiler is the oldest configuration, relying on a cold water storage tank in the loft and a feed-and-expansion tank alongside the cylinder — still found in older London properties that have not been upgraded.
Controls — a room thermostat, thermostatic radiator valves (TRVs) on individual radiators, and a programmer or smart thermostat controlling when the system runs — sit alongside the boiler, radiators and pipework as the fifth core component of the system. Since 2018, Boiler Plus requirements mean new gas boiler installations in England must meet a minimum efficiency standard and include at least one additional control measure, most commonly a smart thermostat.
Scope of work
What we cover
From a single faulty radiator to a full new system in a property converting off electric storage heaters, our Gas Safe registered engineers cover the complete range of central heating work across London.
New central heating installations
Complete new systems for properties being converted from electric or storage heaters, or replacing a system that has reached the end of its life — boiler, radiators, pipework, controls and, where needed, a hot water cylinder, all sized and installed as one coordinated job.
Boiler and system repairs
Diagnosis and repair of no-heat, no-hot-water, low-pressure, leaking and fault-code breakdowns on combi, system and regular boilers. Most repair callouts are completed same-day, with parts carried on the van for common faults.
Radiator upgrades and additions
Swapping undersized single-panel radiators for double-panel or double convector radiators, adding radiators to extensions and loft conversions, and re-balancing the system so every room heats evenly.
Smart controls and TRVs
Smart thermostats, zoned heating controls and thermostatic radiator valves (TRVs) fitted to every radiator, giving room-by-room control and meeting the Boiler Plus control requirement on new boiler installations.
Power flushing
A power flush forces high-velocity water and cleaning chemicals through the system to remove years of accumulated sludge and scale — common in London's hard water areas — restoring flow to cold radiators and protecting a new boiler's warranty.
Cylinder and immersion work
Supply and installation of unvented hot water cylinders for system boiler setups, cylinder replacements, and immersion heater repairs and replacements for properties that need backup or independent hot water heating.
System upgrades and conversions
Converting an old regular (heat-only) boiler and tank system to a combi or unvented system boiler, removing loft cold water tanks where no longer required, and upgrading pipework from imperial to modern 15mm and 22mm copper or push-fit.
Zoning and multi-zone heating
Splitting a property into independently controlled heating zones — typically upstairs and downstairs, or extension versus original house — using zone valves and additional thermostats, reducing wasted heating in unoccupied areas.
Does your system need attention?
Signs your central heating needs attention
London's hard water supply accelerates scale buildup in boilers, pipework and radiators compared with soft water areas of the UK. If you recognise any of the following, book a diagnostic callout before a minor issue becomes a full breakdown in cold weather.
Cold radiators, top or bottom
Cold patches indicate trapped air (top) or sludge and scale buildup (bottom). Left unaddressed, sludge accelerates pump wear and can void a boiler warranty.
Boiler short-cycling
A boiler that fires up, runs briefly, then switches off repeatedly is short-cycling — usually caused by low system pressure, a faulty thermostat, or an oversized boiler for the property, and wastes gas while wearing components faster.
Banging, gurgling or kettling noises
Kettling — a rumbling, kettle-like noise from the boiler heat exchanger — is a classic sign of limescale buildup in hard water areas like much of London, restricting water flow and reducing efficiency.
Uneven heat across rooms
Some rooms warm quickly while others stay cold, often caused by an unbalanced system, a failing pump, or radiators that were never correctly sized for the room during a previous installation.
Rising energy bills without more usage
A boiler losing efficiency, scale buildup reducing heat transfer, or a system running longer to reach set temperature all show up as creeping bills even when heating habits have not changed.
A system over 12–15 years old
Most gas boilers have a realistic service life of 10 to 15 years. Parts availability declines toward the end of this range, and older non-condensing boilers run at markedly lower efficiency than current ErP-rated models.
How it works
Our process, step by step
From free survey to signed-off certificate, here is the sequence we follow on every London central heating installation and major repair.
01
Free survey and heat-loss assessment
A Gas Safe registered engineer visits to assess the property room by room, checks existing pipework, gas supply, flue route and radiator sizing, and — for new systems — carries out a heat-loss calculation rather than guessing boiler size from the old unit.
02
Fixed-price written quotation
You receive an itemised fixed-price quote covering the boiler model and warranty, all radiators and controls, labour, and Building Regulations notification. No day-rate billing and no surprise extras once work starts.
03
System drain-down and strip-out
The existing system is drained and any parts being replaced — boiler, cylinder, radiators, pipework — are removed. Dust sheets and floor protection are used throughout occupied properties.
04
Installation — boiler, pipework and radiators
New pipework is run, radiators are fitted or repositioned, and the boiler is installed with a compliant flue route. Where a cylinder is part of the system, it is plumbed in alongside the necessary pressure and expansion vessels.
05
Commissioning, controls and power flush
The system is filled, inhibitor is added, and — on full new installations — a power flush or system flush is carried out before commissioning to remove installation debris. Controls, TRVs and any smart thermostat are set up and demonstrated.
06
Certification and Building Regulations notification
Gas work is notified through the Gas Safe scheme as required under Building Regulations Part J, and you receive a Benchmark Commissioning Checklist, warranty registration confirmation, and a Building Regulations compliance certificate.
2025 pricing
Central heating costs in London
The following are indicative price ranges for central heating work in London in 2025, inclusive of labour, standard parts, and Building Regulations notification through the Gas Safe scheme. Your fixed price depends on property size, pipework condition and access. All quotes are confirmed at survey — no day-rate billing.
| Job | Price range (2025) | Notes |
|---|---|---|
| Combi boiler replacement (like-for-like) | £2,000 – £3,200 | 1 day, existing pipework and flue route reused |
| Combi boiler + minor pipework changes | £2,800 – £4,200 | Repositioned boiler or upgraded flue run |
| System boiler + unvented cylinder | £5,500 – £9,000 | Larger properties, higher hot water demand |
| Full new central heating system | £4,500 – £9,500 | Boiler, all radiators, pipework and controls |
| Single radiator replacement | £220 – £450 | Per radiator, double-panel upgrade included |
| Power flush (whole system) | £350 – £650 | Depends on radiator count |
| Smart thermostat installation | £220 – £400 | Fitted and configured, Boiler Plus compliant |
| Annual boiler service | £80 – £120 | Single boiler, includes safety checks |
These ranges reflect the London market in 2025 and include commissioning and certification. They do not include structural work, decorating, or replastering beyond reasonable make-good around pipe routes. The survey will confirm your fixed price in writing.
Buyer's guide
Choosing the right heating engineer
Central heating work is a significant spend, and it is an area where homeowners commonly report being oversold — pushed toward a full system replacement when a targeted repair would do. Here is how to protect yourself before agreeing to any quote.
Get two or three written quotes
Never accept the first quote on a job of this size. Citizens Advice and Gas Safe Register both recommend comparing at least two to three written quotes, each itemising the boiler model, warranty length, radiators, and controls included.
Check the Gas Safe Register yourself
Any engineer or business working on gas boilers, gas pipework or flues in the UK must be Gas Safe registered by law. Check the engineer's registration number and photo ID card directly on gassaferegister.co.uk before work begins — do not rely on a card shown on-site alone.
Insist on a heat-loss calculation, not a guess
Correct boiler and radiator sizing should come from a room-by-room heat-loss calculation (or at minimum a proper radiator output check), not simply matching the kW rating of your old boiler. An oversized boiler short-cycles and wastes fuel; an undersized one never heats the property properly.
Question a recommended full system replacement
If an engineer's first response to a single fault or a few cold radiators is "replace the whole system," ask for the specific diagnostic reasoning. A cold radiator, a noisy boiler or reduced hot water pressure is very often resolved by a repair or a power flush rather than wholesale replacement.
Register the manufacturer warranty promptly
Most boiler manufacturers require online warranty registration within 30 days of installation, and some extended warranties (up to 10–12 years) are only available when the boiler is installed and registered by an accredited installer. Confirm who is responsible for registration before work starts.
Watch for red flags
Be cautious of cash-only pricing with no paperwork, pressure to sign on the day of a free "boiler check," quotes with no itemised breakdown, and refusal to provide a Gas Safe registration number in writing. A reputable engineer will always leave time for you to consider a quote.
Get started
Free survey for London central heating
We survey all London central heating enquiries free of charge, including a proper heat-loss assessment for new systems. A Gas Safe registered engineer visits, assesses the full scope, and provides a written fixed-price quotation within 24 hours. No commitment required.
Common questions
Central heating London: frequently asked
How much does a new central heating system cost in London?
A full new central heating system in a typical London property — combi boiler, radiators throughout, pipework and controls — ranges from £4,500 to £9,500 depending on property size and whether you are converting from an older system or replacing like-for-like. A straightforward combi boiler swap on existing pipework starts from around £2,000. A system boiler with an unvented hot water cylinder, more common in larger London houses with higher hot water demand, typically runs £5,500 to £9,000. Your fixed price depends on the number of radiators, pipework condition, and any flue routing or gas supply upgrade needed.
How long does it take to install central heating in a London property?
A combi boiler replacement on existing pipework usually takes 1 day. A full new central heating installation in a 3-bedroom London terraced house — new boiler, all radiators, pipework runs under floors and through walls, and controls — typically takes 3 to 5 working days. Larger properties or system boiler installations with a cylinder can take up to 6 days. We confirm an exact timescale at the survey once we have assessed access, floor construction and the number of radiators involved.
Combi, system or regular boiler — which is right for my London home?
A combi boiler heats water on demand with no cylinder or tank required, and suits most London flats and smaller houses with one bathroom. A system boiler uses an unvented hot water cylinder and is better suited to properties with two or more bathrooms where multiple hot water outlets may run simultaneously. A regular (heat-only) boiler retains a traditional cold water tank in the loft and feed-and-expansion tank, and is typically only recommended where an existing regular system is being retained or where mains pressure is too low for a combi or unvented cylinder. We size and recommend the right system at survey based on your property, hot water demand and existing pipework.
Do I need planning permission or Building Regulations approval for central heating work?
Installing or replacing a gas boiler is notifiable under Building Regulations Part J (combustion appliances) and must be carried out or notified by a Gas Safe registered engineer — no separate planning permission is needed for a standard like-for-like or upgraded installation in most London properties. Listed buildings and properties in conservation areas may have restrictions on external flue positions, so we check this at survey. On completion of gas work, we notify Building Regulations compliance through the Gas Safe scheme and you receive a Building Regulations compliance certificate.
Why are my radiators cold at the top or bottom?
Cold at the top of a radiator with warmth below almost always means trapped air, which is resolved by bleeding the radiator with a bleed key. Cold at the bottom with warmth above usually indicates sludge or debris that has settled in the base of the radiator, restricting flow — this is common in London properties with hard water, where scale builds up in pipework and radiators over years. A power flush clears this sludge from the whole system. If bleeding does not resolve a cold top, the issue may be a faulty thermostatic radiator valve (TRV) or an airlock elsewhere in the system, which we diagnose on a callout.
What is Boiler Plus and does it affect my installation?
Boiler Plus is the government standard (in force since April 2018) that sets minimum efficiency requirements for new gas boilers installed in England, requiring a minimum ErP (Energy related Products) efficiency rating and at least one additional heating control — commonly a smart thermostat, weather compensation, load compensation, or flue gas heat recovery. Every combi boiler installation we carry out in London includes a Boiler Plus-compliant control as standard, most commonly a smart thermostat, which also reduces running costs by giving more accurate control over when and how the system heats your home.
How often should my central heating system be serviced?
An annual boiler service is recommended by every UK boiler manufacturer and is typically a condition of maintaining your warranty. Beyond the boiler itself, a full system service every 1 to 2 years — checking pump operation, TRV function, cylinder (where fitted), and system pressure — helps catch developing faults such as early-stage scale buildup or a failing pump before they cause a breakdown in winter. London properties on hard water mains benefit from more frequent inhibitor and system water checks than properties in soft water areas.
Should I get more than one quote before replacing my whole heating system?
Yes. Getting two to three written quotes is standard advice from Citizens Advice and the Gas Safe Register for any heating installation, and is particularly important given how often London homeowners report being told they need a full system replacement when a repair, power flush, or partial upgrade would resolve the issue. A proper quote should follow a heat-loss calculation (or at minimum a room-by-room radiator sizing check), not a guess based on boiler size alone, and should itemise the boiler model, controls, warranty length and any additional parts such as a filter or new cylinder.