We fit both combi and system boilers across North, West and Central London, and the right choice depends far more on your home than on the boiler itself: how many bathrooms you have, how many people shower in the morning, your mains water pressure, and whether you have room for a hot water cylinder.
⚙️ How Each One Works
- Combi (combination) boiler: one box on the wall does both jobs. Turn on a hot tap and the boiler fires and heats mains water as it passes through. No tanks, no cylinder.
- System boiler: heats the radiators and a hot water cylinder, usually in an airing cupboard. Hot water is stored ready to use, so several taps can run at once.
- Regular (heat-only) boiler: like a system boiler, but with cold water tanks in the loft as well. Common in older houses — and the usual starting point for a conversion.
⚖️ At a Glance
| Combi | System | |
|---|---|---|
| Hot water | On demand, never runs out | Stored in a cylinder, can run out |
| Two showers at once | Flow drops | Yes |
| Space | Boiler only | Boiler + cylinder cupboard |
| Depends on mains pressure | Yes | Less so (unvented cylinders still need good mains) |
| Backup if boiler fails | None | Immersion heater for hot water |
| Install cost (FE) | Swap from £1,900 | From £2,500 with cylinder |
🏡 Which Suits Your Home?
| Your home | Usually best | Why |
|---|---|---|
| Studio, 1–2 bed flat | Combi | Saves space, one bathroom |
| 3-bed house, 1 bathroom | Combi | Handles one shower at a time well |
| 3-bed with en-suite | Either | A larger combi can work if mains flow is good |
| 4+ bed, 2 or more bathrooms | System | Two showers at once without the flow dropping |
| Weak mains pressure or flow | System (or keep existing) | A combi can only deliver what the mains supplies |
| Rented flat / HMO room lets | Combi | Simple, compact, fewer parts to maintain |
💷 What It Costs in London (2026)
| Job | FE Maintenance | Typical London range |
|---|---|---|
| Combi swap (old combi out, new combi in) | from £1,900 | £2,000 – £3,600 |
| New system boiler with hot water cylinder | from £2,500 | £2,800 – £6,000 |
| Conversion: tanks and cylinder to a combi | from £3,500 | Top of the range — more pipework and making good |
Our prices are the total — no VAT added. The typical ranges come from published 2026 London price guides. What moves the price:
- The boiler you choose and its output (sized to your radiators and hot water needs).
- Moving the boiler to a new position, or a new flue route.
- Gas pipe size — a new boiler often needs a larger gas supply pipe than the old one.
- Cleaning the system first if there’s sludge — see radiators cold at the bottom.
- Conversions — removing loft tanks and the cylinder, capping pipes and making good.
We give you a free quote on the phone, then a fixed price before any work starts. New boilers come with up to a 10-year warranty. Full breakdown: boiler replacement cost in London.
🔄 Thinking of Converting to a Combi?
Swapping an old tank-and-cylinder system for a combi frees up the airing cupboard and the loft, and you get mains-pressure hot water. It’s worth it in most flats and smaller houses. Think twice if:
- you have two or more bathrooms used at the same time;
- your mains flow is weak (common in some older London streets and upper-floor flats);
- you rely on the immersion heater as a backup;
- you’re planning solar panels or a heat pump later — both work best with a cylinder.
⚖️ The Rules
- Only a Gas Safe registered engineer can install a gas boiler. Check the engineer’s ID card.
- A new boiler is notifiable building work. Your Gas Safe installer registers it, and you receive a Building Regulations compliance certificate by post.
- New gas boilers must be condensing boilers, fitted with suitable controls.
- Register the boiler with the manufacturer to activate its warranty, and keep up the annual service — most warranties depend on it.
- Landlords: after a new boiler, you still need the annual gas safety certificate.
🏆 New Boilers from FE Maintenance
- Gas Safe registered and fully insured — every engineer works directly for FE Maintenance, no subcontractors
- Combi swap from £1,900, system boiler with cylinder from £2,500, conversion from £3,500
- Up to 10-year warranty on new boilers
- Free quote on the phone, then a fixed price before we start; prices are the total, no VAT added
- Boiler service from £80 to keep it running and the warranty valid
- Free online client portal — your certificates stored in one place, with reminders before renewals. See how it works
We cover North, West and Central London. See our gas and boiler services or ask for a quote.
Typical ranges are based on published 2026 London price guides; FE prices are starting prices and depend on the boiler and the property. General information for homes in England, as of October 2026.
Frequently Asked Questions
Get a Free Boiler Quote
Gas Safe registered engineers across North, West and Central London. Combi swap from £1,900, system boiler with cylinder from £2,500, up to 10-year warranty — free quote on the phone.
info@femaintenance.com · 171 Crescent Road, Barnet EN4 9RN