Baxi 800 Combi 2 Boiler Cost with Installation

This reliable, British-made combi boiler from Baxi offers a 10-year warranty as standard which is longer than most competitors provide without upgrades. 

The Baxi 800 Combi2’s ultra-compact design (just 285mm deep) fits into standard kitchen cupboards, and it’s notably lightweight at under 30kg. The Baxi 800 was voted as our best combi boiler for engineer feedback and comes in three output sizes: 24kW, 30kW, and 36kW. 

It includes an Adey MagnaClean Micro2 filter in the box, saving you £100-150 on installation extras, and features EasyFill permanent filling and an external pressure gauge for straightforward maintenance.

See further specifications for the Baxi 800 Combi 2 below:

Baxi 800 Combi 2 Product Table
	Available Outputs	24kW	30kW	36kW
	Type	Combi	Combi	Combi
	Fuel	Gas	Gas	Gas
	Condensing	Yes	Yes	Yes
	Efficiency rating (%)	93	93	93
	ErP	A	A	A
	LPG compatible	Yes	Yes	Yes
	Standard guarantee	10 years*
	Max output (kW)	24	30	36
	Flow rate (l/min)	10.2	12.2	15
	Mounting	Wall-mounted
	Dimensions (mm)	700 x 395 x 285
	Typical price (incl. VAT)	£1,300	£1,400	£1,500
	Typical installation cost (incl. VAT)	£800 – £1,400
	Total cost	£2,100 – £2,900

*Terms and conditions apply.

Baxi 800 Combi 2 overview

The Baxi 800 Combi 2 is Baxi’s top combi model. As a combination boiler, it handles both central heating and hot water on demand – no separate tanks required. At 700mm high and 285mm deep, it fits into a standard 290mm kitchen cupboard. The lightweight design (29.2kg) makes installation easier than heavier alternatives.

Baxi 800 Combi 2 Range
Model output size	House size	Bathrooms	Radiators
24kW	Flats, small homes 1 to 3 bedrooms	1	Up to 10
30kW	Small-medium homes 3 to 4 bedrooms	1-2	Up to 15
36kW	Medium homes 3 to 5 bedrooms	2	Up to 20

Flow rates range from 10.2 to 15 litres per minute. The 36kW model with its 15 l/min flow rate is notably powerful for a mid-range combi, suitable if you have two bathrooms in regular use.

Matching output to your actual usage is essential. An oversized boiler will cycle wastefully, whilst an undersized model struggles to meet demand during peak usage, resulting in lukewarm water when multiple taps are running.

The 36kW model’s 15 l/min flow rate is one of the strongest in this price bracket – worth considering if you need reliable hot water for two bathrooms.

Key benefits at a glance

• ErP A-rated efficiency (93%)
• Compatible with Baxi uSense smart thermostat
• Adey MagnaClean Micro2 filter included as standard
• Resistant brass hydraulics
• Stainless steel heat exchanger 
• Compact design (285mm deep)
• Quiet operation
• EasyFill permanent filling link
• Pre-heated condensate trap that prevents freezing
• External analogue pressure gauge
• OpenTherm compatible
• LPG compatible (no conversion kit required)
• Hydrogen-ready (certified for 20% blend)
• 10-year standard warranty*

Baxi 800 Combi 2 technical specifications

The standout component is the brass hydraulics block. Baxi uses brass rather than the plastic or aluminium found in budget boilers. Brass is more corrosion-resistant, handles temperature variations better, and has a longer service life.

Output and efficiency ratings

All three models operate at 93% efficiency, which is strong for mid-range boilers. This is a substantial improvement over older boilers that typically achieve just 70-75% efficiency. Over a year, that efficiency difference translates to roughly £150-200 in energy savings for an average home.

The 24kW suits smaller homes with one bathroom. The 30kW handles medium homes with a bathroom and ensuite. The 36kW is designed for larger properties where two bathrooms are regularly used simultaneously – and at 15 l/min flow rate, it maintains solid pressure even when both showers run at once.

Baxi doesn’t offer the wide modulation range of premium brands like Viessmann (which achieves 10:1 modulation), but the boiler is OpenTherm compatible. When paired with a compatible smart thermostat, it modulates output well by ramping down during mild weather rather than constantly switching on and off. This smoother operation means less wear on components and slightly lower running costs over time.

Dimensions 

The boiler measures 700mm high, 395mm wide, and 285mm deep. That 285mm depth is compact – it fits into a standard kitchen cupboard with adequate room for pipework. 

At 29.2kg, it’s light enough for two people to lift onto the mounting bracket without difficulty.

Components included

The Adey MagnaClean Micro2 filter comes included. This is a £100-150 component that protects your heating system by capturing metallic debris before it can damage the boiler. Most manufacturers require separate purchase of this filter but Baxi includes it as standard.

However, you must install and register the filter at the same time as the boiler, or your 10-year warranty drops to just 2 years.

The EasyFill permanent filling link is a practical feature as you can top up system pressure yourself without calling an engineer. Combined with the external analogue pressure gauge, this allows straightforward personal pressure management.

The pre-heated condensate trap is worth noting. It pre-heats condensate before it exits the boiler, which significantly reduces the risk of frozen pipes during winter; frozen condensate is one of the most common causes of boiler failure during cold weather.

Smart control compatibility is available via the optional Baxi uSense WiFi thermostat – though this isn’t built into the boiler as standard. The Baxi 800 Combi 2 is also compatible with OpenTherm and works with popular smart thermostats like Nest, allowing you to control and monitor your heating remotely.

The boiler is hydrogen-ready for 20% blend and can be manually converted between natural gas and LPG without purchasing a conversion kit. The conversion is handled through software, which saves £40-60 compared to boilers requiring physical conversion kits which is a big plus.

Prices and installation costs

Unit prices range from £1,200 to £1,400 depending on output, with installation typically costing around £1,200. These prices include a standard horizontal flue and the Adey MagnaClean Micro2 filter.

Vertical flues that exit through the roof add £300-400 to the cost due to additional labour and roofing work required.

Baxi 800 Combi 2 Costs
Output size	Unit cost (incl. flue)	Total (incl. installation)
24kW	£1,300	£2,500
30kW	£1,400	£2,600
36kW	£1,500	£2,700

Warranty and support

The Baxi 800 Combi 2 comes with a 10-year standard warranty on parts and labour. This is the maximum warranty period Baxi offers, and they provide it as standard on this model – demonstrating confidence in its durability.

The critical requirement: you must install and register the Adey MagnaClean Micro2 filter at the same time as the boiler. Without this, coverage drops to 2 years.

Annual servicing by a Gas Safe registered engineer is also required to maintain warranty coverage, and the Benchmark commissioning paperwork must be completed. Without documented proof of annual servicing, warranty claims will be rejected.

Baxi also offers a Platinum Package that extends warranty coverage to 12 years. This package requires installation by a Baxi Approved Installer and includes additional servicing benefits. However, for most homeowners, the standard 10-year warranty (which is already longer than most competitors offer as standard) provides adequate coverage. 

💡 WhatPrice Insight: Unlike some manufacturers where 10-year warranties require specially trained installers or additional purchases, Baxi’s 10-year warranty is available with any Gas Safe engineer, provided the Micro2 filter is registered correctly.

Installation information

Standard installation costs average around £1,200 for straightforward replacements. Costs increase for boiler relocations, pipework upgrades to meet current regulations, or complex flue routing.

What to expect on installation day

If additional work is required – such as upgrading pipework or relocating the boiler – your installer should explain this clearly beforehand, including any impact on cost or installation time.

Do you need a system flush or filter?

Yes – under UK Building Regulations, it is now a mandatory requirement to thoroughly clean and flush a central heating system before a new boiler is installed.

Luckily, the Adey MagnaClean Micro2 filter is included with the boiler, meeting the legal requirement for filter installation. You won’t need to purchase this separately, which equates to a £100-150 saving compared to boilers that don’t include filters as standard.

A system flush isn’t legally required but is recommended for older systems. Flushing costs £350-800 and removes accumulated rust and sludge that can reduce efficiency and potentially damage the new boiler if left in the system.

Finding a Gas Safe registered engineer

All gas boiler installations must be completed by Gas Safe registered engineers by law. Baxi is one of the UK’s most popular brands, so parts are widely available and most engineers have experience with these boilers.

Use the WhatPrice quote service to be matched with vetted, Gas Safe registered installers in your area. 

Reviews and ratings

Baxi maintains a 4.6 out of 5 star rating on Trustpilot UK – one of the highest scores among boiler manufacturers. That rating is based on thousands of reviews, which gives you a reasonable picture of what actually matters to homeowners once the boiler’s been running for a year or two.

The 800 Combi 2 specifically receives consistent feedback on a few core themes: warranty accessibility; the included filter; and compact installation.

Positive reviews

The 10-year standard warranty receives frequent praise. Homeowners appreciate getting a decade of coverage without paying extra or requiring specially trained installers.

The included Adey MagnaClean Micro2 filter is regularly highlighted as valuable – both for the cost saving and for the protection it provides to the heating system.

The compact dimensions (285mm deep) fit into spaces where deeper boilers won’t. The lightweight design makes installation quicker and easier.

The EasyFill permanent filling link is well-received – users value being able to top up system pressure themselves using the external gauge rather than paying for engineer call-outs.

The 36kW model’s 15 l/min flow rate receives praise from homeowners with two bathrooms. Users report that pressure remains adequate even during simultaneous shower usage.

Quiet operation is frequently mentioned – even when installed in kitchen cupboards, the boiler is barely audible during operation.

Negative reviews

The main complaint concerns response times from Baxi’s customer service during winter. Getting an engineer to attend can take 48 hours or more during peak breakdown season, which is frustrating when heating is unavailable.

The LCD display isn’t backlit, making it difficult to read in dark cupboards. Some users resort to using torches to check settings or error codes.

Whilst the boiler is OpenTherm compatible, it doesn’t achieve the wide modulation range of premium brands. It cycles on and off more frequently than models with 10:1 modulation, though this doesn’t significantly impact most users.

Some homeowners report pressure loss issues during the first year, requiring frequent use of the EasyFill link to top up. This is usually a system issue rather than a boiler fault, but users tend to attribute it to the boiler itself.

💡 Top Tip: Book your annual service well before winter. Otherwise you’ll be competing with emergency call-outs for available appointment slots.

How the Baxi 800 Combi 2 compares

The Baxi 800 sits in the mid-range market alongside the Worcester Bosch Greenstar 4000 and competes with Viessmann’s premium Vitodens 100-W. Each has different strengths – warranty length, modulation technology, included components, built-in smart features – and the right choice depends on what you actually prioritise.

Baxi 800 Combi 2 Comparison Table
Model	Baxi 800 Combi 2	Worcester Bosch Greenstar 4000 Combi	Viessmann Vitodens 100-W Combi
Typical unit price	£1,400	£1,200	£1,400
Heat exchanger	Stainless Steel	Aluminium	Stainless Steel
Standard warranty	10 Years	5 Years	5-7 Years
Max warranty	12 Years	10 Years	10-12 Years
Built-in WiFi	No (uSense optional)	Yes	Yes
Cupboard fit?	Yes	No (Slightly taller)	Yes

Final thoughts – is the Baxi 800 Combi 2 right for you?

The Baxi 800 Combi 2 is a strong choice in the mid-range market. You’re getting build quality, a 10-year warranty as standard, and the Adey MagnaClean Micro2 filter included which alone saves £100-150.

The 10-year warranty is easy and accessible. Unlike Viessmann where extended warranties require trained installers, Baxi provides the full ten years with any Gas Safe engineer (you just need to ensure the filter is registered correctly at installation).

The brass hydraulics are a strong selling point. Budget boilers use plastic components that deteriorate faster; Baxi’s brass construction can handle years of temperature cycling more reliably.

Compared to the Worcester Bosch Greenstar 4000, which costs slightly less, you’re receiving double the standard warranty coverage (10 years vs 5 years). Baxi also includes the magnetic filter that Worcester requires as a separate purchase. Worcester offers built-in WiFi and has a more extensive nationwide installer network, which are important factors to take into consideration, but Baxi provides better value on core specifications.

Against the Viessmann Vitodens 100-W, Baxi costs about the same but offers a longer standard warranty (10 years vs 5-7 years). Viessmann provides better modulation (10:1 ratio) and built-in WiFi, but for homeowners who are prioritising warranty protection, Baxi’s position is stronger.

The compact 285mm depth fits where deeper boilers can’t, whilst the 29.2kg weight makes installation quicker, potentially reducing labour costs.

The Baxi 800 Combi 2 boiler suits small to large homes where homeowners value long warranty protection and genuine value for money. The 36kW model’s 15 l/min flow rate in particular offers two-bathroom properties with regular simultaneous usage superior hot water delivery.

It’s less suitable for users who value built-in smart features (WiFi is an optional extra via uSense) or want maximum modulation range for the smoothest possible operation. Baxi’s engineer network, whilst extensive, isn’t quite as dense as Worcester Bosch’s in some regions.

For a well-engineered British boiler with proper warranty protection and valuable components included as standard, the 800 Combi 2 delivers.

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