Baxi 600 System 2 Boiler Cost with Installation

The Baxi 600 System 2 is the mid-range system boiler in Baxi’s lineup – the sweet spot between the budget-focused 400 series and the premium 800, which comes in at a higher price with a 10-year warranty.

What makes the 600 System 2 stand out in its class is what’s under the casing: a stainless steel heat exchanger, brass hydraulics, and built-in pipe concealment, all at a price that won’t leave you wincing. Add a 7-year standard warranty with any Gas Safe engineer and LPG compatibility without a conversion kit, and this is a serious contender for medium-sized homes that need a cylinder-fed hot water solution.

Discover more of the Baxi 600 System 2 specifications below:

Baxi 600 System 2 Product Table
		615 (15kW)	618 (18kW)	624 (24kW)
	Available outputs	15kW	18kW	24kW
	Type	System	System	System
	Fuel	Gas / LPG	Gas / LPG	Gas / LPG
	Condensing	Yes	Yes	Yes
	Efficiency rating (%)	93	93	93
	ErP	A	A	A
	LPG compatible	Yes (no kit)	Yes (no kit)	Yes (no kit)
	Standard guarantee	7 years*
	Max output (kW)	15	18	24
	DHW flow rate	Determined by cylinder
	Mounting	Wall-mounted
	Dimensions (mm)	700 x 395 x 285
	Weight	28.1-29.5kg
	Typical price (incl. flue)	£1,200	£1,250	£1,350
	Typical installation cost (incl. VAT)	£1,500
	Total cost	£2,700	£2,750	£2,850

*Terms and conditions apply.

Baxi 600 System 2 overview

A system boiler works differently from a combi: rather than heating water on demand directly from the mains, it heats water and sends it to a separate hot water cylinder for storage. The upside is volume, a cylinder gives you a ready supply of hot water that multiple bathrooms can draw on at the same time, without the flow rate ceiling that limits any combi at peak times. It’s the natural choice for three or four-bedroom homes where the morning rush means two showers running at once.

The 600 System 2 comes in three outputs: 15kW for smaller homes with a cylinder already in place, 18kW for the typical three-bedroom family home, and 24kW for larger properties with higher heat loss. All three share the same compact 285mm-deep casing and include the built-in pipe concealment bracket that keeps the install looking clean in a cupboard.

The boiler is compatible with Baxi’s own cylinder range (including the Direct and Indirect Cylinder) and the Megaflo Eco range – useful if you’re specifying the full system from one manufacturer. If you’re doing a like-for-like system boiler replacement, expect the job to take a day. Converting from a combi with no existing cylinder? Budget for more time and a new cylinder on top.

Baxi 600 System 2 Range
Model	Suitable for	Radiators	Notes
615 (15kW)	Small homes, 1-2 bedrooms	Up to 10	Best for smaller properties with an existing cylinder
618 (18kW)	Medium homes, 3 bedrooms	Up to 15	The most commonly fitted model
624 (24kW)	Larger homes, 3-4 bedrooms	Up to 20	For properties with higher heat demand

Output selection for a system boiler is based on your property’s heat loss – not the number of bathrooms. The cylinder handles hot water capacity; the boiler handles the heating circuit. Your Gas Safe engineer will run a heat loss calculation at survey stage. For most three-bedroom homes, the 618 is the right starting point.

Key benefits at a glance

• ErP A-rated efficiency (93% efficient)
• Stainless steel heat exchanger – better corrosion resistance than aluminium
• Brass hydraulics block throughout
• 7-year standard warranty with any Gas Safe engineer – no premium installer tier required
• LPG compatible via software conversion – no kit, no extra cost
• Built-in pipe concealment bracket for a clean cupboard installation
• Front-access servicing – no need to remove the boiler from the wall
• Backlit LCD display with simple twist controls
• OpenTherm compatible – pairs with Baxi uSense 2
• Fully modulating burner
• Pre-heated condensate trap – reduces risk of frozen pipes in winter
• External analogue pressure gauge for easy self-top up
• Frost protection built in
• Central top flue with extensive options up to 20m
• Hydrogen blend ready (up to 20%)

Baxi 600 System 2 technical specifications

For those who want to know what’s actually going on under the casing, the 600 System 2 has a couple of features that punch above its price point.

The stainless steel heat exchanger is the headline – at this price, most rival system boilers use aluminium, which is fine in normal conditions but less forgiving in hard water areas where limescale and corrosion accelerate wear.

The brass hydraulics block is the other one worth knowing about: brass manages temperature cycling and corrosion better than the plastic or composite hydraulics you’ll find in cheaper boilers.

Output and efficiency ratings

All three models run at 93% efficiency, ErP A-rated. As condensing boilers, they recover heat from exhaust gases that older non-condensing boilers would simply push out through the flue – which is why homeowners replacing a pre-2005 installation often see a meaningful drop in gas bills within the first few months. The 93% figure is consistent across all three outputs, so going up from a 618 to a 624 doesn’t cost you anything in running efficiency – it just gives you more capacity for the heating circuit.

The fully modulating burner is the 600 System 2’s everyday superpower. Rather than firing at full output and then cutting off when the thermostat is satisfied, it turns itself down to match what the system actually needs. Less cycling, more even heat distribution, and less wear on components over time.

Paired with an OpenTherm thermostat like the Baxi uSense 2, the modulation gets smarter still – the thermostat and boiler communicate directly, so the boiler always knows exactly how hard to work.

Dimensions

All three outputs share the same footprint: 700mm tall, 395mm wide, and 285mm deep. At 29.5kg it is light enough for two engineers to position in a cupboard without difficulty. The 285mm depth fits a standard kitchen cupboard, and the built-in pipe concealment bracket routes connections behind the boiler body.

What’s under the casing

The stainless steel heat exchanger sits at the core of the system. Stainless steel is more resistant to the condensate that forms during the condensing process, and it handles limescale build-up better than aluminium in hard water areas.

The brass hydraulics block connects the heat exchanger to the central heating circuit. Brass is denser and more corrosion-resistant than the plastic or composite alternatives, and it handles the repeated thermal expansion and contraction of daily use without degrading as quickly.

The pre-heated condensate trap is a practical cold-weather feature. Standard condensate traps can freeze during prolonged cold spells, causing the boiler to lock out at precisely the moment you need it most. Baxi pre-heats the trap before condensate enters it, significantly reducing that risk on exposed or unheated pipe routes.

The external analogue pressure gauge sits outside the casing, so you can check system pressure at a glance without opening any panels. Paired with the filling link, it makes topping up the system straightforward enough to do yourself – cutting out the engineer call-out that a pressure drop would otherwise require.

The backlit LCD display shows operating status, temperatures, and fault codes in plain text. Smart control is available via the optional Baxi uSense 2 WiFi thermostat (remote scheduling and energy tracking via the My Baxi app) or the Baxi AmbiZen thermostat. The boiler is also OpenTherm compatible with Nest, tado, and Honeywell for full weather and load compensation.

Prices and installation costs

The Baxi 600 System 2 costs approximately £1,200 for the 15kW, £1,250 for the 18kW, and £1,350 for the 24kW – all including a standard horizontal side-wall flue. If you need a vertical roof flue instead, budget an additional £300-£500. For LPG properties, the conversion is software-only – no kit, no extra parts, saving £40-£60 compared to boilers that need a physical conversion kit.

Using a mid-range installation figure of £1,500:

Baxi 600 System 2 Costs
Output size	Unit cost (incl. flue)	Total (incl. installation)
615 (15kW)	£1,200	£2,700
618 (18kW)	£1,250	£2,750
624 (24kW)	£1,350	£2,850

💡Tip: These prices assume a like-for-like system boiler replacement with an existing cylinder in place. Need a new cylinder? A new unvented cylinder adds £500-£1,000 plus fitting. Converting from a combi with no existing cylinder can add up to £2,000 to the total project cost – see our system boiler cost guide at for a full breakdown.

These prices are indicative, based on our research and actual boiler prices submitted to WhatPrice by homeowners. Get quotes from at least three Gas Safe registered installers, or use the WhatPrice Boiler Cost Calculator for a guide price.

Warranty and support

The warranty is seven years, parts and labour, with any Gas Safe engineer. No Baxi Assure tier needed – just register the boiler within 30 days of installation and service it annually. That’s one of the most accessible warranty structures at this price point.

Annual servicing by a Gas Safe engineer is the main condition to keep the warranty active. Miss a service and you risk invalidating the cover, so it’s worth setting a reminder or taking out a service plan at installation.

💡 WhatPrice Insight: The Baxi 600 System 2 sits a level below the 800 System, which carries a 10-year warranty as standard. If you’re planning to stay in the property for over 7 years, the 800 System is worth pricing up alongside – the step up in warranty length is meaningful on a component you expect to run for a decade or more.

Installation information

A like-for-like system boiler replacement on existing pipework is a one-day job. The 600 System 2’s compact dimensions and front-access design make it one of the more straightforward installs in this class.

If you’re fitting a new cylinder at the same time, expect one to two days and confirm your installer holds a G3 unvented hot water qualification alongside their Gas Safe registration.

What to expect on installation day

Do you need a system flush or filter?

UK Building Regulations require a magnetic filter on any new boiler installation. A magnetic filter captures iron oxide and metallic debris before it reaches the heat exchanger – particularly worth getting right with a stainless steel exchanger you want to last. Budget £80-£120 for a quality filter from Fernox, Adey, or Baxi’s own range.

A powerflush of existing pipework isn’t legally required, but on any system over ten years old we’d strongly recommend it. Connecting a new boiler to a system full of sludge is a bit like fitting new brake pads on a car with contaminated fluid – it undermines the investment from day one. Budget £350-£800 depending on the number of radiators.

Finding a Gas Safe registered engineer

All gas boiler installations must be carried out by a Gas Safe registered engineer. For a new unvented cylinder, your installer also needs a G3 qualification – worth confirming at the quoting stage rather than on installation day. Use the WhatPrice quote service to be matched with vetted, Gas Safe registered installers in your area.

Reviews and ratings

Baxi holds a 4.6 out of 5 rating on Trustpilot UK, based on over 76,000 reviews. System boiler-specific feedback is broader than model-specific, but the themes are consistent.

Positive reviews

Engineer quality is the standout positive. Owners consistently describe Baxi engineers as prompt and thorough, with faults diagnosed and resolved on the first visit in the majority of accounts. An 800 System owner replacing an older Ideal boiler reports faster heat-up times, quieter operation, and lower running costs within two years. An experienced installer singles out the 600 Series specifically as among the best-value system boilers on the market, noting the stainless steel heat exchanger and build quality as particular strengths.

Negative reviews

Noise comes up more than once. A 624 System owner describes the boiler as considerably louder than its predecessor – loud enough to disturb sleep on the other side of the house – with a Baxi engineer confirming the noise level was normal for the model. Worth considering if the installation position is close to a bedroom.

Warranty enforcement is the other recurring frustration. Claims are rejected on technical grounds when conditions aren’t met – one owner had a fan failure declined because the annual service was a couple of months overdue, despite four years of warranty remaining. The 30-day registration window and annual servicing requirement are enforced strictly, not as formalities. Confirm the warranty conditions in writing from your installer before the job starts.

How the Baxi 600 System 2 compares

Baxi 600 System 2 Comparison Table
Model	Baxi 600 System 2	Baxi 800 System	Worcester Bosch Greenstar 4000 System
Typical unit price (18kW)	£1,250	£1,100	£1,100
Heat exchanger	Stainless steel	Stainless steel	Aluminium
Standard warranty	7 years	10 years	5 years
Max warranty	7 years	10 years	10 years
Built-in WiFi	No	No	Yes
App control	uSense 2 (optional)	uSense 2 (optional)	EasyControl (built-in)
LPG compatible	Yes (no kit)	Yes (no kit)	Yes
Max output	24kW	24kW	24kW

For personalised guidance on choosing the right boiler, we recommend speaking with a Gas Safe registered engineer.

Final thoughts – is the Baxi 600 System 2 right for you?

The 600 System 2 earns its place as the best-value stainless steel system boiler in the Baxi range. At £1,250 for the 618 with a 7-year warranty, brass hydraulics, and LPG-ready from the factory, it sits at a similar price to the Worcester Bosch Greenstar 4000 System and still brings a better heat exchanger material to the table.

The honest conversation to have before buying is about the 800 System. The 800 costs around £250 more for the comparable output and extends the warranty to 10 years. Over a 10-15 year ownership period, that extra three years of cover has real value. If you’re planning to stay in the property for more than seven years, price both. If the budget is the deciding factor or the timeline is shorter, the 600 System 2 is the right call.

Against the Worcester Bosch Greenstar 4000 System, the 600 System 2 is £250 cheaper and brings a stainless steel heat exchanger against Worcester’s aluminium. Worcester counters with built-in WiFi, a 1:10 modulation ratio, and one of the most extensive Accredited installer networks in the UK. If smart connectivity from day one matters to you, Worcester is the stronger specification. If you want the better heat exchanger material and a longer standard warranty at a lower price, Baxi wins that comparison.

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