Combi replacements, system boilers, back boiler conversions and gravity-to-combi conversions across Greenwich — SE3, SE7, SE9, SE10 and SE18. Find directory-listed Gas Safe registered heating engineers below.
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What a boiler installation actually involves
A boiler installation involves assessment, commissioning and regulatory documentation — not just replacing the appliance. In older properties — including Greenwich’s Victorian and Edwardian terrace stock where pipe runs are non-standard and system configurations may not have been assessed in decades — surveys are particularly important because pipework layouts and historic alterations may affect installation complexity.
Greenwich Council confirms that only Gas Safe-registered people can fit, alter or remove gas appliances or pipework.¹
A proper installation covers:
Registration with Building Control and issue of the Gas Safe Building Regulations Compliance Certificate. Removal and safe disposal of the existing boiler. Full assessment of system requirements, including radiator output, flow rates, flue positioning and appropriate boiler sizing.
Specification of the correct boiler output in kilowatts for your property. Supply and fitting of the new boiler and, where appropriate, a magnetic system filter and scale-reduction measures suitable for hard water areas. A system clean may be recommended before installation, particularly on older systems or where required by manufacturer warranty conditions.
Commissioning, testing and completion of the Benchmark checklist. Building Regulations Part L requires minimum energy efficiency controls for new boiler installations. Depending on the system design, this may include measures such as weather compensation, load compensation or smart heating controls.
The compliance documentation matters: when you sell your property, your solicitor will ask for the Building Regulations Compliance Certificate — the documentation generated following notification of the installation through the Gas Safe competent person scheme. Any installer who doesn’t mention Building Regulations notification and certification unprompted is not someone you want fitting a boiler — the documentation is legally required and they should be raising it before you ask.
When Greenwich homeowners replace their boiler
Age-related failure is the most common category. A boiler over 15 years old that has broken down, been condemned at its last service, or is beyond economic repair.
This is particularly common in Plumstead and Eltham where significant amounts of pre-2000 housing stock still runs on original or early-replacement units. Many installers report increased emergency replacement demand during autumn and early winter — planning a replacement ahead of the colder months can avoid emergency-install pricing and limited availability.
Efficiency-driven upgrade is the second category — homeowners moving from G-rated or F-rated boilers to modern A-rated units. Modern high-efficiency boilers may reduce fuel consumption compared with older non-condensing models.
One clarification worth making: the government’s Boiler Upgrade Scheme does not fund gas boiler replacements. The scheme currently covers air source, ground source and water source heat pumps (up to £7,500), air-to-air heat pumps (£2,500 residential), and biomass boilers (£5,000, for properties off the gas grid).⁴ The government also launched the Clean Heat Market Mechanism in April 2025, which requires boiler manufacturers to match a rising proportion of their boiler sales with heat pump installations — a scheme that may influence boiler pricing as manufacturers adjust to their obligations.⁵ In many Greenwich Victorian terraces, heat pump installation can require additional insulation upgrades, emitter upgrades or external-unit space, which may increase installation complexity and cost compared with a like-for-like gas boiler replacement.
System conversion is the most complex category. Greenwich has a significant number of properties in Blackheath, Charlton and Kidbrooke still running on back boilers, gravity-fed hot water cylinders or outdated system configurations — these conversions involve additional pipework and labour that benefit from a detailed itemised breakdown.
Back boiler removal, gravity-to-combi conversion and cylinder removal all involve additional pipework and labour that a lump-sum quote will bury. Always ask for a line-by-line breakdown on a conversion job.
Why boiler choice matters more in Greenwich
Greenwich’s hard water profile affects which boiler and which accessories make sense for your home, and is worth discussing with your installer at the survey stage.
Thames Water says most water supplied across London and the South East is hard.² In hard water areas, magnetic system filters on the central heating return and scale-reduction measures on the cold water inlet can help reduce sludge and limescale-related wear within the heating system.
Many manufacturers — including Worcester Bosch, Vaillant and Ideal — recommend magnetic system filters as part of modern installation practice, and some warranty conditions may reference system protection requirements. Failure to follow manufacturer installation and commissioning requirements may affect warranty eligibility. Installers may recommend different models depending on water conditions and system configuration.
What to expect from a boiler installation
The survey — before installation day.** The installer visits, assesses your current system, checks radiator output and sizing, confirms flue position, and specifies the correct boiler output. In a Victorian terrace in Woolwich or Charlton where pipe runs and system configurations are frequently non-standard, a survey-based quote helps avoid revisions once installation begins.
Installation day. Old boiler out. System cleaned where appropriate — either a power flush or a chemical flush with magna-cleanse. New boiler, system filter and scale-reduction measures fitted where suitable.
System filled, commissioned and tested. Radiator balancing helps a condensing boiler operate more efficiently across the heating system, particularly in older properties where original pipe runs may have varied flow characteristics.
On completion. You receive the manufacturer’s warranty documentation, a completed Benchmark commissioning checklist, and the Gas Safe Building Regulations Compliance Certificate. If any of these documents are missing, homeowners should request them before signing off the installation. Missing compliance documentation can create delays or additional enquiries during property sale transactions.
💡 Pro tip: Before your installer arrives, check whether your radiators have been balanced and bled recently. Cold spots may indicate sludge in the system — and fitting a new boiler without flushing first can push that sludge through the new heat exchanger. Ask your installer about a power flush or magna-cleanse if they have not already raised it. Many installers recommend a system clean before fitting a new boiler, particularly on older heating systems.
Typical costs for boiler installation in Greenwich
What boiler installation costs in Greenwich — 2026
Greenwich and SE London pricing sits at the higher end of national ranges. Typical 2026 figures:
| Service | Typical London range 2026 |
|---|---|
| Like-for-like combi replacement | £2,800–£4,500 supply and fit |
| System boiler installation | £3,000–£4,800 supply and fit |
| Back boiler or gravity system conversion | £3,200–£5,000+ |
| Magnetic system filter (fitted) | £150–£250 |
| Power flush or magna-cleanse | £300–£500 |
Typical straightforward combi replacement in Greenwich: £2,800–£3,500 all-in including filter, commissioning and Gas Safe registration.
If a quote comes in significantly below these ranges, ask what has been included or excluded. Customers should request a full itemised breakdown before agreeing any installation work.
Frequently asked questions — Boiler Installation Greenwich
Depends on your property and hot water demand. Combis heat water on demand — no cylinder needed, ideal for smaller homes and flats with one bathroom. System boilers work with a hot water cylinder and suit larger properties or homes with multiple bathrooms where simultaneous demand is high.
If you are in a larger Eltham semi or a converted Woolwich terrace with multiple bathrooms, the combi versus system question matters significantly — get it assessed properly before anything is ordered.
A straightforward like-for-like combi replacement typically takes one full day. A system conversion — removing a back boiler, relocating pipework, or changing from a gravity-fed system — typically runs to two days.
Any installer quoting a timeline before seeing the property is guessing. Confirmed timelines come after the survey — especially in older terrace properties where pipework layouts and conversion scope can’t be assessed remotely.
Warranty periods vary by manufacturer, model and installation conditions, with many major brands offering multi-year warranties when installed and registered correctly. The warranty is only valid if installed by a Gas Safe registered engineer, commissioned correctly, and — in many cases — fitted with a magnetic system filter.
Check what the warranty requires before agreeing a boiler model, and ensure your installer registers the unit on your behalf on completion.
No. The Boiler Upgrade Scheme does not fund gas boiler replacements.⁴ The scheme currently covers heat pumps (£7,500 for air source, ground source and water source; £2,500 for air-to-air, residential only), and biomass boilers (£5,000, for off-grid properties). Gas boiler installations are not within scope.
In many Greenwich Victorian terraces, heat pump installation can require additional insulation upgrades, emitter upgrades or external-unit space, which may increase installation complexity and cost compared with a like-for-like gas boiler replacement. Your installer can advise on what is realistic for your specific property.
Older systems may benefit from cleaning or flushing before a new boiler is fitted, particularly where sludge, cold spots or circulation problems are present. Sludge and magnetite built up in old pipework can circulate through the new boiler, reducing efficiency and potentially affecting manufacturer warranty conditions.
Cleaning the system before installation may help reduce sludge-related issues affecting the new boiler. Many installers recommend a system clean before fitting a new boiler, particularly on older heating systems.
Areas We Cover
Boiler installation engineers on this directory cover the full Greenwich borough. Find local help below:
- Boiler Installation North Greenwich
- Boiler Installation Charlton
- Boiler Installation Woolwich
- Boiler Installation Eltham
- Boiler Installation Blackheath
- Boiler Installation Kidbrooke
- Boiler Installation Abbey Wood
- Boiler Installation Thamesmead
- Boiler Installation Plumstead
- Boiler Installation Shooters Hill
Related guides
A new boiler is a significant decision. In a Plumstead terrace or a Kidbrooke semi, a suitable installer assesses the property requirements, installs the system correctly, and provides the required documentation — including the Gas Safe Building Regulations Compliance Certificate and the Benchmark commissioning checklist. Work guarantees available where offered — confirm with your installer.
Contact verified heating engineers in Greenwich ↑
Sources & further reading
Last reviewed: May 2026 by Adiel Khan — SFEDI-accredited business advisor 20+ years experience (South East Enterprise Ltd) and operator of VerifiedPlumbers. [LinkedIn ↗]
This page is reviewed against guidance published by ¹ Royal Borough of Greenwich — Repairing a problem when we cannot help https://www.royalgreenwich.gov.uk/housing/request-repair/repairing-problem-when-we-cannot-help
² Thames Water — Hard water https://www.thameswater.co.uk/help/water-and-waste-help/water-quality/hard-water
³ Gas Safe Register — Find or check a Gas Safe registered engineer https://www.gassaferegister.co.uk/find-an-engineer-or-check-the-register/
⁴ GOV.UK — Apply for the Boiler Upgrade Scheme: What you can get https://www.gov.uk/apply-boiler-upgrade-scheme/what-you-can-get
⁵ GOV.UK — Clean Heat Market Mechanism https://www.gov.uk/government/consultations/clean-heat-market-mechanism-revisions-ahead-of-scheme-year-2-20262027