British Gas quoted my neighbour £3,400 last month to swap his Worcester 28i for a Worcester 4000 in the same location. I did the same job, same boiler, four days later for £2,650. He didn't think the British Gas engineer was a crook — he thought the British Gas engineer was, well, British Gas. And he was right.
This is a guide to the real, 2026 cost of a new combi boiler installation in Wembley, drawn from six recent jobs I've done across HA9, HA0 and NW10. I'll show you the headline price, what's actually in the price, and what makes one quote 80% more than another for the same appliance.
The three tiers most Wembley homes fall into
These are all-in prices. They include the boiler, supply, fit, like-for-like flue, system flush, magnetic filter, chemical inhibitor, commissioning with a flue gas analyser, building-control notification, and warranty registration. They do not assume any heroic plumbing — just a sensible like-for-like swap in the same location.
Six real installs · 2026 prices
Install 1 · 1-bed flat, Wembley Park HA9 · £1,895
Replacing a 14-year-old Worcester 28i Junior that finally gave up. Same location (kitchen wall), same flue (rear, through external wall), same gas pipe size (15mm — adequate for 25kW). Worcester Greenstar 2000 25kW, 7-year warranty registered with Worcester. One day on site, finished by 4pm. Customer paid the £30 deposit, balance on completion.
Install 2 · 2-bed terrace, Sudbury HA0 · £2,150
Like-for-like Vaillant ecoTEC Pro 28 for Vaillant ecoTEC Plus 832. Existing 22mm gas pipe (good), but the flue had to be extended by 600mm to clear a new bedroom extension built next door. £250 extra for flue extension and additional bracketing. 10-year warranty.
Install 3 · 3-bed semi, Kingsbury NW9 · £2,650
The full Monty. Replacing a 22-year-old Potterton back boiler behind a gas fire with a kitchen-wall combi. Relocation work: new gas pipe from meter to kitchen (8m of 22mm), new flue through external wall, condensate run to drain, electrical spur, plus capping off the old back-boiler and removing the gas fire. Worcester 4000 30kW, 10-year warranty. Two days on site.
Install 4 · 4-bed Edwardian, Harrow HA1 · £3,250
Existing Vaillant ecoTEC swapped for a Worcester 8000 Life 35kW (customer wanted the 12-year warranty and the quieter operation). Long horizontal flue (4.2m, requiring an additional support kit), gas pipe upgrade to 28mm from meter to first reduction, new system filter and condensate-trap relocation. 12-year warranty.
Install 5 · 1-bed flat, Park Royal NW10 · £1,895
Identical to Install 1 — Worcester Greenstar 2000, 25kW, like-for-like in the same kitchen cupboard. No surprises.
Install 6 · 2-bed Wembley HA9 · £2,250
Worcester 4000 25kW. Like-for-like position. Customer also wanted a Hive Mini thermostat fitted (£185 supplied and configured), bringing the total to £2,435. Without the thermostat: £2,250.
Asbestos removal (rare, but found in Wembley 1930s terraces in airing cupboards and around old back-boiler flues — £400–£900 to a licensed remover); gas-meter upgrades (rare; only if your meter is over 6m³/hr and you're going to a 35kW+ boiler); structural building work around the flue route. I'll always price these as separate line items if you need them, so you can decide.
Why one quote is £1,895 and another is £3,400 for the same boiler
The difference is almost never the appliance. It's three things, in this order:
1. Overheads
British Gas pay engineers PAYE, have a national fleet, run TV adverts, and carry head-office salaries. Hometree, BOXT, Heatable et al. take a margin between the customer and the engineer that actually does the work. A local Gas Safe sole trader has a van, a phone and an annual Gas Safe registration. The same boiler, same hours of work, same warranty — different cost structure behind it.
2. What's silently excluded
The headline price on a national-chain quote often excludes things that protect your warranty. The classic three:
- Magnetic system filter. Worcester, Vaillant and Ideal all require one for the 10-year warranty. A MagnaClean Pro2 is £85 retail and £150 fitted — and yet some quotes "include the boiler only".
- Chemical inhibitor (Sentinel X100 or equivalent). Required by the manufacturer. £25 of chemical, £40 fitted. Skipping it voids the warranty if you ever claim.
- Full system flush. Worcester's 10-year warranty is conditional on a power flush or a chemical clean documented in the install record. "Power flushing extra" on a quote means they're hoping you'll skip it and lose the warranty quietly.
3. The flue route
The single most-priced variable across my six installs above. A like-for-like rear flue is free in any quote. A new horizontal flue is £150–£350. A vertical flue through the roof is £450–£700. A relocation from an old back boiler to a kitchen wall (Install 3 above) is £700–£1,200 of extra labour, pipework and flue parts. Get this priced specifically before you compare quotes.
Want a real, itemised quote?
Send me a photo of your current boiler and a rough sketch of where the flue exits the building. I'll come back with a fixed itemised quote within 24 hours — no upsells.
Which boiler should I actually choose?
Three honest rules of thumb after 1,200+ installs and repairs in Wembley:
- For most 1- and 2-bed flats: Worcester Greenstar 2000 25kW. The cheapest reliable combi on the market. The 7-year warranty is fine in practice — they almost never fail in those seven years.
- For most 2- and 3-bed houses: Worcester 4000 or Vaillant ecoTEC Plus. Quieter, better hot-water flow, 10-year warranty. The sweet spot.
- For 4-bed houses or two-bathroom homes: Worcester 8000 Life or Viessmann Vitodens. If you have any chance of running two showers at once, you need the heat exchanger to keep up.
What I almost never fit:
- Worcester 8000 in a small flat. It's a beautiful boiler. It's also wildly oversized for a 1-bed and will short-cycle (turn on and off rapidly) which kills the heat exchanger.
- Cheap Chinese-rebranded "value" boilers. The £1,200 supply-and-fit deals you see on Gumtree. Parts dry up after 4 years, no manufacturer warranty in practice, can't sell the house easily.
- Combi when a system boiler would be better. Two-bathroom homes with low mains pressure often need a system boiler with an unvented cylinder, not a 40kW combi. I'll tell you before I take the job.
Right-sizing: kW matters more than brand
Oversizing is the most common installer error in Wembley. A 35kW boiler in a 1-bed flat will short-cycle, condense more (which means more condensate dripping to drain), make more noise, cost more to buy, and won't last as long. Bigger isn't better — it's just more expensive at every step.
What to ask before you sign
Three questions that filter out 80% of dodgy quotes:
- "Can I see this written down with the boiler model, warranty length, and what's included and excluded?" A real installer will email you a one-page itemised quote within an hour. A dodgy one will say "I'll email it" and never send it.
- "Is the system flush included? And the magnetic filter? And the inhibitor?" All three should be included on any quote over £1,800. If any are missing, you're losing your warranty.
- "What happens if you find a problem during install — say the gas pipe needs upgrading?" The honest answer: "I'll show you the issue, give you a fixed price for it, and you decide. Never start unauthorised work." The dodgy answer: "It'll come out in the wash."
Frequently asked questions
How much does a new combi boiler cost in Wembley in 2026? +
For a typical Wembley 2-bed property, a Worcester Bosch Greenstar 2000 starts at around £1,895 fully fitted with a 10-year manufacturer warranty. A mid-range Vaillant ecoTEC Plus or Worcester 4000 sits at £2,250–£2,650. A premium Worcester 8000 Life or Viessmann Vitodens is £3,100–£3,650. The largest variable is the flue route, not the appliance.
Why is one quote £1,895 and another £3,400 for the same boiler? +
Three reasons: national-chain overheads, silently-excluded items (filter, inhibitor, flush) that void the warranty, and unpriced flue work. Always get the parts list itemised.
What is included in the £1,895 install price? +
Supply and fit of a Worcester Bosch Greenstar 2000 25kW, like-for-like flue, magnetic filter, inhibitor, full flush, commissioning, warranty registration, building notification, and 12-month workmanship guarantee. Excludes asbestos removal, gas-meter upgrades and long flue extensions.
How long does a combi boiler installation take? +
One full working day (8am–5pm) for a like-for-like swap. Two days for a relocation (e.g. back boiler to kitchen wall). Heat and hot water are back on by the end of day one in every install I do.
Which combi boiler is best for a Wembley flat? +
For most 1- and 2-bed Wembley flats, a Worcester Bosch Greenstar 2000 25kW. For 3-bed houses, step up to a Worcester 4000 30kW or Vaillant ecoTEC Plus. For 4-bed houses, a Worcester 8000 or Viessmann Vitodens. Never oversize.
Do you offer 0% finance on boiler installations? +
I don't sell finance directly — it adds 15–20% to the price for the brokerage margin. If you need to spread the cost, your bank's standard personal loan rate is almost always cheaper than the "0% interest" deals from big installers (which roll the interest into the headline price).
Written by Jamil — Gas Safe registered engineer (Reg. 930067), based in Wembley HA9. Prices accurate as of May 2026; check the latest figures by phone. Last updated 5 May 2026.