Baxi Duo-tec Compact Combi Boiler Cost with Installation

From Baxi’s established Duo-tec line, the compact combi is straightforward and – as the name suggests – designed for snug spaces. The 7-year parts and labour warranty applies as standard with any Gas Safe registered engineer, which makes it a practical choice for landlords and homeowners who want solid coverage without navigating additional qualification requirements. All three models share a 285mm depth and 700mm height, and LPG versions are available across the range without a conversion kit.

Discover more of the Baxi Duo-tec Compact combi specifications below:

Baxi Duo-tec Compact Combi Product Table
	Available outputs	25kW	30kW	36kW
	Type	Combi	Combi	Combi
	Fuel	Gas	Gas	Gas
	Condensing	Yes	Yes	Yes
	Efficiency rating (%)	92	92	92
	ErP	A	A	A
	LPG compatible	Yes	Yes	Yes
	Standard guarantee	7 years
	Max output (kW)	25	30	36
	Flow rate (l/min)	10.2	12.2	15.0
	Mounting	Wall-mounted
	Dimensions (mm)	700 x 390 x 285
	Typical price (incl. VAT)	£1,100	£1,250	£1,350
	Typical installation cost (incl. VAT)	£1,200
	Total cost	£2,300	£2,450	£2,550

*Terms and conditions apply.

Baxi Duo-tec Compact Combi overview

The Baxi Duo-tec Compact is designed for properties where a reliable, cupboard-fit combi is needed without paying for the latest technology. At 285mm deep and 700mm tall, it fits the majority of standard kitchen units, and as a combi boiler it delivers heating and hot water from the mains with no separate cylinder or cold water tank required.

The range covers three outputs: 25kW for smaller homes and flats, 30kW for the typical two to three bedroom home, and 36kW for larger properties. The 7-year parts and labour warranty does not require a Baxi Assure registered installer – only registration within 30 days of installation and annual servicing by a Gas Safe engineer.

Baxi Duo-tec Compact Combi Range
Model output size	House size	Bathrooms	Radiators
25kW	Flats, 1 to 2 bedrooms	1	Up to 10
30kW	Small to medium homes, 2-3 bedrooms	1 & ensuite	Up to 15
36kW	Medium homes, 3-4 bedrooms	2	Up to 20

It’s important to choose the right output for your hot water demand, otherwise the boiler can run inefficiently. The 25kW model delivers 10.2 l/min, adequate for a small home or flat with a single bathroom and moderate hot water demand. The 30kW reaches 12.2 l/min, which suits a family home with one bathroom and occasional ensuite use without difficulty. The 36kW tops out at 15.0 l/min and is the right choice if two bathrooms are in regular use.

Key benefits at a glance

• ErP A-rated efficiency (92% efficient)
• Compact cupboard-fit design
• Stainless steel heat exchanger
• Brass hydraulics 
• 7-year parts and labour warranty as standard*
• Lightweight at 30.3kg 
• Backlit LED display with simple twist controls
• Rigid filling link for straightforward pressure top-ups
• LPG compatible 
• OpenTherm compatible
• Compatible with Baxi uSense 2 smart thermostat
• Frost protection built in
• Hydrogen ready (certified for 20% blend)

Baxi Duo-tec Compact Combi technical specifications

The core components are a primary heat exchanger for central heating, a stainless steel plate heat exchanger for domestic hot water, brass hydraulics, a modulating burner that adjusts output to match demand, and an OpenTherm interface for smart thermostat compatibility. Controls are front-mounted and straightforward, featuring a backlit LED display.

Output and efficiency ratings

All three models have a 92% ErP A-rated efficiency. As condensing boilers, they recover heat from exhaust gases that older non-condensing boilers expelled.

The boiler is fully modulating, meaning it adjusts its output to match the heating demand rather than cycling on and off at full power. Paired with a compatible OpenTherm thermostat such as the Baxi uSense 2, this modulation can be tailored to your specific hot water demands, reducing energy waste and evening out temperature swings.

Dimensions

At 700mm tall, 390mm wide, and 285mm deep, the Duo-tec Compact fits the majority of standard kitchen cupboards. 

With a weight of 30.3kg, it is manageable for two engineers to lift into position in tight cupboard installations.

Components included

The Duo-tec Compact uses a dual heat exchanger, with the primary heat exchanger handling central heating. A separate stainless steel heat exchanger manages the domestic hot water.. Brass hydraulics are the final component, a more durable choice than the plastic hydraulic blocks found in lower-priced alternatives.

The rigid filling link allows homeowners to top up system pressure themselves without calling an engineer out. Combined with the front-mounted backlit LED display, which shows operating status and error codes clearly, this keeps maintenance straightforward.

Smart control is available via the optional Baxi uSense 2 WiFi thermostat, purchased separately at around £100-£150, which allows remote heating management through the My Baxi app. The boiler is also OpenTherm compatible, so it works with Nest, Tado, and Honeywell thermostats.

The Duo-tec Compact is LPG compatible without a conversion kit, and is certified for use with up to a 20% hydrogen blend, in line with the current direction of the UK gas grid.

Prices and installation costs

The Baxi Duo-tec Compact combi costs approximately £1,100 for the 25kW, £1,250 for the 30kW, and £1,350 for the 36kW. With installation costs of around £1,200, the total cost of the boiler and installation can cost anywhere between £2,300 and £2,550.

The Duo-tec Compact sits at the accessible end of the mid-range combi market. Our prices include a standard horizontal side-wall flue. A horizontal flue adds around £100-£150 to the cost; a vertical roof flue can exceed £500 due to the additional complexity involved.

Using a mid-range installation figure of approximately £1,200:

Baxi Duo-tec Compact Combi Costs
Output size	Unit cost (incl. flue)	Total (incl. installation)
25kW	£1,100	£2,300
30kW	£1,250	£2,450
36kW	£1,350	£2,550

These prices are indicative only, based on our research and actual boiler prices submitted to WhatPrice by homeowners. 

To get an accurate price based on your needs, request quotes from at least three Gas Safe registered installers. They can advise you on the best boiler type for your home and give you tailored estimates to compare. 

Alternatively, use the WhatPrice Boiler Cost Calculator to get a guide price for your installation.

Warranty and support

The Duo-tec Compact’s 7-year warranty is activated by registration within 30 days of installation. It does not require a premium installer tier – any Gas Safe registered engineer can carry out the installation and the full 7-year cover stands, provided the boiler is registered and serviced annually. Without documented proof of annual servicing, warranty claims may be rejected.

Extended warranty options beyond 7 years are available through Baxi Assure registered installers, though for most homeowners the standard 7-year cover provides adequate protection at this price point.

Installation information

A standard like-for-like combi swap typically costs around £1,200 and can be completed in a day. At 30.3kg dry lift weight, the Duo-tec Compact is manageable for two engineers to position in most cupboard installations without difficulty.

What to expect on installation day

Do you need a system flush or filter?

Under UK Building Regulations, fitting a magnetic filter is mandatory when installing a new boiler. A magnetic filter captures metallic debris and sludge before it can reach the boiler’s internal components – and unlike the Baxi 800 Combi 2, the Duo-tec Compact does not include one in the box, so this is an additional purchase to factor in at quoting stage.

A powerflush is a separate process that cleans existing pipework and radiators before the new boiler is connected. It is not mandatory, but is strongly recommended on systems over ten years old, as a new boiler connected to a dirty system will work harder than it should and may develop faults sooner.

Budget £350-£800 for a powerflush and around £100-£120 for a compatible magnetic filter.

💡 WhatPrice Insight: Unlike the Baxi 800 Combi 2, the Duo-tec Compact does not include an Adey MagnaClean Micro2 filter in the box. A compatible magnetic filter must be purchased and fitted separately – budget around £100-£120 – to satisfy the UK Building Regulations requirement and protect the heat exchangers over time.

Finding a Gas Safe registered engineer

All gas boiler installations must be carried out by a Gas Safe registered engineer. Baxi is one of the UK’s most widely serviced brands, so parts are readily available and the majority of Gas Safe engineers are already familiar with the Duo-tec. 

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. Duo-tec specific feedback has been collated and broken down below:

Positive reviews

Longevity is the most common thread in the Duo-tec reviews. Multiple owners report running the same boiler for ten plus years before a significant fault develops – and in several cases the first serious repair was still covered under warranty because the boiler had been serviced annually throughout. 

When repairs are needed, engineer experience draws praise, with owners regularly highlighting that Baxi engineers arrive with the relevant parts already stocked in the van and resolve faults in a single visit. Several reviewers mention the warranty being honoured without difficulty when the boiler had a full service history – including one owner whose central heating stopped working after three years, with the faulty components replaced at no cost.

Negative reviews

A small number of reviews describe difficulty getting a resolution when faults arose, with promised callbacks not materialising and email contact going unanswered. These tend to relate to complex or contested warranty situations rather than routine repairs, but they are worth noting for owners who may need to escalate a claim.

A small number of reviews mention reliability issues in the five-to-seven-year range. Annual servicing helps catch these early before they become breakdowns.

How the Baxi Duo-tec Compact Combi compares

Baxi Duo-tec Compact Combi Comparison Table
Model	Baxi Duo-tec Compact	Baxi Platinum Compact	Worcester Bosch Greenstar 4000
Typical unit price	£1,250	£1,450	£1,200
Heat exchanger	Stainless steel	Stainless steel	Aluminum
Standard warranty	7 years	10 years	7 years
Max warranty	10 years	10 years	10 years
Built-in WiFi	No	No	Yes
App control	Baxi uSense 2	Baxi uSense 2	Bosch EasyControl
Cupboard fit	Yes	Yes	Yes
Max output/bathrooms	36kW / 2 bathrooms	36kW / 2 bathrooms	36kW / 1 & ensuite bathrooms

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

Final thoughts – is the Baxi Duo-tec Compact combi right for you?

The Duo-tec Compact’s case is simple: a 7-year warranty accessible to any Gas Safe engineer, a price starting at around £1,100 for the 25kW including flue, and a design that engineers across the country know well. For like-for-like natural gas or LPG combi replacements where the priority is reliable cover at a competitive installed cost, it delivers.

The 92% efficiency sits two points below the Worcester Bosch Greenstar 4000 (94%), and the controls are more basic – no built-in WiFi, no touchscreen, no app as standard. For homeowners who want those features, the Worcester Greenstar 4000 is around £100 less for the comparable output and adds connectivity as standard. For those who do not, the Duo-tec Compact is the more practical choice.

Within the Baxi range itself, the Platinum Compact sits directly above the Duo-tec and is worth considering before committing. For around £200 more on the 30kW once the cost of a separately purchased filter is factored in, it adds an Adey MagnaClean Micro2 filter in the box and extends the standard warranty to 10 years. 

Against the Worcester Bosch Greenstar 4000, the Duo-tec Compact is around £50 more expensive on the comparable output but carries a longer standard warranty (7 years vs Worcester’s 5-year baseline before filter and Accredited installer upgrades are added), and gives up built-in WiFi and a slightly higher efficiency figure. The balance tips in Worcester’s favour for homeowners who want smart control from day one; in the Duo-tec’s favour for those prioritising warranty accessibility and ease of servicing.

FAQ