A new boiler is one of the bigger bills most homeowners face, and the quotes can vary wildly for what looks like the same job. This guide sets out what a replacement typically costs across Bexley, Sidcup, Welling and Erith, and explains why two neighbours on the same road can pay very different amounts.
For a straightforward like-for-like combi swap in a Bexley home, most people pay somewhere between £2,000 and £3,200 fully fitted. That covers a mid-range boiler, a magnetic filter, a system flush, new flue and fittings, Gas Safe commissioning and the Building Regulations notification. A premium brand with a longer manufacturer warranty pushes the figure towards £3,500 or more.
System and heat-only boilers tend to cost a little less for the appliance but the surrounding work often adds up, particularly if the cylinder or expansion vessel needs replacing at the same time. Converting from a conventional system to a combi is a bigger job again, usually £3,500 to £5,000, because the cylinder and tanks come out, pipework is rerouted and the mains water supply has to be checked for pressure and flow.
The boiler itself is often less than half the total. Labour is the bulk of the rest, and labour is driven by how awkward the install is. A boiler in a kitchen with the flue straight through the wall and the gas run already the right size is a half-day job for two people. One tucked in a loft, an airing cupboard on the top floor, or a bedroom with the flue needing to reach a specific clearance from windows takes longer and needs more materials.
Older housing stock around Bexleyheath, Sidcup and Barnehurst regularly throws up a 15mm gas supply that no longer meets current requirements for a modern combi, so the gas run needs upgrading to 22mm. Sludge in old radiators means a proper power flush rather than a quick cleanse, which can add £300 to £600 but protects the warranty. Vertical flues through a pitched roof, condensate pumps where there is no drain nearby, and plume kits to keep steam away from a neighbour's window are all common extras in terraced and semi-detached homes.
Bigger is not better with a combi. A 24kW to 30kW unit suits most two and three bedroom homes with one bathroom. If you have two bathrooms and want decent shower pressure in both at once, a 35kW combi or a system boiler with an unvented cylinder is the more honest answer, and the price should reflect that.
Ask any installer to explain the sizing rather than just matching whatever is on the wall now. Many older boilers in the area were oversized, and replacing like for like wastes gas every winter. A heat loss calculation takes twenty minutes and stops you paying for output you will never use.
Insist on a written, itemised quote. It should name the boiler model, list what is included, and state whether a magnetic filter, flush, thermostat and Building Regulations registration are in the price. A quote that just says 'new boiler £1,800' almost always has something missing, and it tends to appear on the final invoice.
Check the Gas Safe register for the engineer who will actually turn up, not just the company. Ask what manufacturer warranty comes with the boiler and whether the installer is accredited to offer the extended version. Finally, ask how they intend to leave the old system: capped, removed, or left for you to deal with.
A simple combi swap is usually done in a day. Conversions, relocations or jobs needing a power flush and new gas run typically take two to three days.
Often yes. A ten year manufacturer warranty on a mid-range boiler can be worth several hundred pounds over its life, provided you keep up with annual servicing so it stays valid.
Government schemes such as ECO4 are aimed at low income households with inefficient heating and are worth checking if you receive certain benefits. For most homeowners, finance through the installer or a manufacturer is the more realistic route.
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