Fixed prices · Gas Safe registered
Boiler Installation & Replacement in South London
When a boiler reaches the end of its life, the right replacement is the one sized for your home - not the one a salesperson wants to shift. As a Gas Safe registered engineer, InstaGasWorks installs high-efficiency combi and system boilers across South London, each one sized properly for your rooms, radiators and hot water demand.
Every new boiler starts with a free survey and a written fixed quote. A straightforward combi-for-combi swap starts from £2,500, and that price already includes a powerflush of the system, a magnetic filter, a limescale reducer, one heating control free, and a 10-year manufacturer warranty that is extended by a further 2 years when fitted by InstaGasWorks - 12 years in total. Most quotes leave those off and bill for them later. Converting an older conventional system is quoted after the survey, because pipework and flue routes vary house to house.
Boiler Installation prices
Boiler installation (combi swap)
From £2,500
Like-for-like replacement of an existing combi. Includes:
- One heating control included FREE
- 2 extra years' warranty FREE when fitted by InstaGasWorks - 12 years in total
- 10-year manufacturer warranty as standard
- Powerflush of the heating system
- Magnetic filter supplied and fitted
- Limescale reducer fitted
- Old boiler removed and disposed of
- Free survey and written quote first
System conversion
Free survey & quote
Replacing an older conventional or back-boiler setup:
- Free home survey first
- Boiler sized properly for your home
- New pipework and flue routes as needed
- Old system removed and disposed of
- Written fixed quote before anything is booked
Controls & thermostats
£150
Install and upgrade heating controls and thermostats. One control is included free with a new boiler installation - this price is for controls fitted on their own, or for additional controls.
Radiator installation
From £150 per radiator
- New radiator fitted
- Valves fitted
- System bled
- Tested and balanced
Every installation is confirmed with a written quote before anything is booked - the price you sign is the price you pay.
Before & after
Before
AfterWhich boiler is right for your home?
Combi boilers
Heat water on demand with no tanks or cylinders - the right answer for most flats and terraced homes, and the installation InstaGasWorks fits most often.
System boilers
Pair with a hot water cylinder to feed multiple bathrooms at once. The better choice for larger family homes where two showers can run at the same time.
Conventional replacements
Older homes with loft tanks and gravity-fed pressure can usually be converted to mains-pressure hot water - you'll get an honest answer on whether it's worth it.
Before & after: cylinder upgrade
A tired vented cylinder and its tangle of old pipework, swapped for a modern unvented cylinder and clean copper - mains-pressure hot water at every tap.
Before
AfterHow a new boiler happens
Step 1
Free survey
Your engineer visits, checks your current system, pipework and flue route, and talks through what you actually need - including whether a repair still makes more sense.
Step 2
Written fixed quote
You get a clear itemised price in writing. No pressure, no follow-up sales calls - take your time comparing it.
Step 3
Installation day
Most combi-for-combi swaps are finished in a single day. Your old boiler is removed and disposed of, and the system is checked end to end before your engineer leaves.
Step 4
Handover & paperwork
The installation is registered, and your engineer walks you through the controls. Annual servicing from £120 keeps the manufacturer warranty valid.
Boiler Installation questions, answered
How much does a new boiler cost?
A straightforward combi-for-combi swap starts from £2,500. That includes a powerflush of the system, a magnetic filter, a limescale reducer, one heating control free, removal of the old boiler, and a 10-year manufacturer warranty, extended by 2 further years when InstaGasWorks fits it - 12 years in total. Converting an older conventional system costs more depending on pipework and flue routes, so your home is surveyed free of charge and you get a written quote before anything is booked.
How long does a boiler installation take?
Most like-for-like combi swaps are completed in a single day. Conversions from a conventional system with tanks and a cylinder usually take longer because pipework has to be re-run - your written quote will say exactly how long the job takes.
Which boiler brands do you install?
All the major brands - Vaillant, Worcester Bosch, Ideal, Baxi and more. At the survey, InstaGasWorks recommends the model that fits your home and budget rather than pushing a single brand.
Do you remove the old boiler?
Yes - removal and disposal of your old boiler is included in every installation quote, along with making good the pipework where the old unit came out.
Will my new boiler have a warranty?
Yes, your boiler comes with its manufacturer warranty, and an annual service - from £120 with InstaGasWorks - is what keeps that warranty valid year to year.
More questions? Read the full FAQ or call for advice over the phone.
Related services: Boiler Repair · Powerflush
Available across: Battersea · Putney · Balham · Tooting · Wandsworth · Clapham · Streatham · Wimbledon · Colliers Wood · Morden · Dulwich · Croydon · Thornton Heath · Norbury · Sutton · Mitcham · Carshalton · Wallington · All areas covered
Same-day availability
Speak to a Gas Safe engineer today
Fixed prices agreed before any work starts — book online with the card above, or talk it through first.