Viessmann Vitodens 100-W Combi Boiler Cost with Installation

If you’ve been eyeing the Vitodens 050-W, the 100-W is where Viessmann really demonstrates what premium modulation technology can do. You’re getting the same strong stainless steel Inox-Radial heat exchanger, built-in WiFi for app control, but with a game-changing 10:1 modulation ratio (versus the 050-W’s 1:8) that lets the boiler run quietly at very low outputs. 

See further specifications for the Viessmann Vitodens 100-W combi below:

Viessmann Vitodens 100-W Combi Product Table
	Available outputs	26kW	30kW	35kW
	Type	Combi	Combi	Combi
	Fuel	Gas	Gas	Gas
	Condensing	Yes	Yes	Yes
	Efficiency rating (%)	94	94	94
	ErP	A	A	A
	LPG compatible	Yes	Yes	Yes
	Standard guarantee	5-to-7 years*
	Max output (kW)	26	30	35
	Flow rate (l/min)	10.5	12.2	14.3
	Mounting	Wall-mounted
	Dimensions (mm)	700 x 400 x 360
	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.

Viessmann Vitodens 100-W combi overview

The Viessmann Vitodens 100-W is exceptionally well-built and impressively quiet, making it an ideal heating solution for homeowners who value long-term reliability.

As an all-in-one combi boiler, it delivers both central heating and hot water directly from the mains, so you can say goodbye to bulky hot water cylinders or cold water tanks in the loft. At just 700mm high, it’s designed to tuck away neatly inside a standard kitchen cupboard without any modifications needed.

Viessmann Vitodens 100-W Combi Range
Model output size	House size	Bathrooms	Radiators
26kW	Flats, small homes 1 to 3 bedrooms	1	Up to 10
30kW	Small-medium homes 3 to 4 bedrooms	1-2	Up to 15
35kW	Medium homes3 to 5 bedrooms	2	Up to 20

With hot water flow rates ranging from 10.5 to 14.3 litres per minute, the Viessmann Vitodens 100-W combi is well-suited to homes with one to two bathrooms. The 26kW handles single-bathroom homes comfortably, whilst the 30kW and 35kW models can manage two bathrooms – though you might notice a slight pressure drop if both showers are running simultaneously.

Bigger isn’t always better when it comes to boiler output. The kW rating should match your actual hot water needs. An oversized boiler will cycle on and off more frequently in a smaller home, which wastes gas and creates unnecessary wear on internal components. An undersized model, on the other hand, will struggle to deliver adequate hot water when demand peaks.

Key benefits at a glance

• ErP A-rated efficiency (94%)
• 10:1 modulation ratio
• Built-in Wi-Fi with ViCare app control
• Stainless steel Inox-Radial heat exchanger with separate 10-year warranty
• MatriX-Plus burner with Lambda Pro combustion control
• Compact, cupboard-friendly design (700mm high)
• Excellent hot water flow rates (up to 14.3 l/min)
• Quiet operation
• LCD touchscreen with built-in frost protection
• OpenTherm compatible 
• LPG compatible (software conversion, no kit required)
• Hydrogen-ready (20% blend)
• 5-to-7-year standard warranty, extendable to 10-12 years*

Viessmann Vitodens 100-W combi technical specifications

For those who like to know exactly what’s happening under the casing, this is where the Vitodens 100-W really demonstrates why Viessmann has such a strong reputation in the heating industry. It isn’t just about looking sleek in your kitchen cupboard; it’s about what’s happening inside to keep your bills low, your showers hot, and your heating system running smoothly for the next decade.

The standout feature here is the combination of the Inox-Radial stainless steel heat exchanger and the 10:1 modulation ratio. Whilst the 050-W already uses stainless steel (putting it ahead of many aluminium-based competitors), the 100-W adds significantly more intelligent power management. You’re getting a boiler that can genuinely think for itself and adjust output smoothly without constant on-off cycling.

Here are the key technical specs for each model in the range:

Output and efficiency ratings

The Viessmann Vitodens 100-W combi is available in 26 kW, 30 kW and 35 kW output sizes, offering flexibility for a wide range of property types. All models are ErP A-rated, operating at around 94% efficiency. This is a meaningful improvement over older non-condensing boilers that typically achieve just 60-70% efficiency, translating to roughly £200-250 in energy savings per year for an average household compared to a 15-year-old boiler.

Across the range, the Vitodens 100-W benefits from a 10:1 modulation ratio – this is where it differentiates itself from budget and mid-range alternatives. The modulation ratio means the boiler can reduce its output to just 2.6kW (on the 26kW model) when demand is low. For instance, during mild autumns when you need heating but not much of it, the boiler can run continuously at very low output rather than cycling on and off repeatedly.

Most budget boilers can’t modulate below 15-20% of maximum output, forcing them to switch on and off every few minutes. That constant cycling is less efficient, creates more wear on components over time, and is considerably noisier. The practical result of the 100-W’s wider modulation is smoother, quieter operation – you don’t hear the boiler firing up and shutting down repeatedly. It just runs continuously at low output, which is both more pleasant to live with and more economical over a 10-year lifespan.

Dimensions 

The Vitodens 100-W is designed to be compact and unobtrusive. All models in the range share the same dimensions: measuring 700 mm high, 400 mm wide, and 360 mm deep. Whilst this is slightly deeper than the 050-W (which is 300mm), it still fits comfortably into standard kitchen cupboards with adequate room for pipework connections.

Components included

With the Viessmann Vitodens 100-W combi, we believe the standout feature is its built-in Wi-Fi connectivity as standard. Unlike many boilers that require you to purchase an additional smart thermostat costing £120-150, the 100-W connects directly to Viessmann’s ViCare app, allowing you to adjust heating schedules and monitor energy usage remotely using your phone or tablet. 

At the heart of the boiler is Viessmann’s stainless steel Inox-Radial heat exchanger, a component the brand is particularly well known for across their entire range. What makes the 100-W special is that this heat exchanger comes with its own dedicated 10-year warranty, separate from the boiler’s main warranty.

Stainless steel offers strong resistance to corrosion and temperature, which is especially important in hard-water areas where limescale buildup can significantly reduce the lifespan of aluminium heat exchangers found in other combi boilers. Voted our best combi boiler for longevity with its stainless steel heat exchanger, it’s clear the Vitodens 100-W stands out for its component build quality.  

The MatriX-Plus burner with Lambda Pro combustion control is how Viessmann maintains peak efficiency across varying conditions. This system automatically adjusts based on actual demand. In practice, this helps keep heating consistent and efficient, even as usage changes throughout the day, and contributes to the noticeably quieter operation compared to budget alternatives.

For added reassurance, the 100-W includes built-in frost protection, which monitors temperature and fires up the boiler if conditions drop dangerously low. This is particularly useful for installations in garages, lofts, or properties that sit empty during winter months. It’s not a feature you might need often, but when cold temperatures hit it can prevent frozen pipes and the expensive damage that comes with them.

The boiler is fully OpenTherm compatible, which means it works properly with smart thermostats like Nest, Hive, and Tado. This allows the thermostat and boiler to communicate intelligently about modulation, allowing the boiler to run at lower outputs rather than just switching on and off. 

It’s also hydrogen-ready for up to 20% hydrogen blend, providing some future-proofing as the UK gas grid potentially transitions.

Prices and installation costs

The typical unit price for the Viessmann Viodens 100-W combi is: £1,300 for the 26kW model; £1,400 for the 30kW model; and £1,500 for the 35kW.

This price usually includes the boiler unit and a standard horizontal flue. The flue is a critical component that safely directs combustion gases outside your home; whilst a standard side-wall flue costs roughly £100, a vertical roof flue can exceed £500 due to the increased complexity of the installation and roofing work required.

Ultimately the standard installation cost is around £1,200, which is the price we’ve used in our cost breakdown below:

Viessmann Vitodens 100-W Combi Costs
Output size	Unit cost (incl. flue)	Total (incl. installation)
26kW	£1,300	£2,500
30kW	£1,400	£2,600
35kW	£1,500	£2,700

These prices are only indicative, based on our research. To get an accurate price based on your needs, you should request quotes from at least 3 Gas Safe registered installers. They can advise you on the best boiler type for your home and give you tailored estimates to compare. 

Warranty and support

The warranty is one of the strongest selling points for the Viessmann Vitodens 100-W, providing a level of protection that exceeds many competitors in this price bracket. The boiler typically comes with a 5-to-7-year standard parts and labour warranty as long as it is registered within 30 days of installation. However, what sets the 100-W apart is the potential to extend this to 10-12 years.

The extended warranty is unlocked when the unit is fitted by a Viessmann Trained Installer and registered through the official portal. The exact warranty length depends on your installer’s accreditation level, but the key point is that you can access this extended protection without paying additional fees, unlike some manufacturers who charge hundreds more for similar coverage.

A huge plus is the separate, 10-year guarantee on the Inox-Radial stainless steel heat exchanger which comes as standard across the more premium models in the Vitodens range. A warranty on the most critical component provides peace of mind, especially in hard water areas where heat exchanger failure is more common. To keep this protection active, you must ensure the boiler receives an annual service by a Gas Safe registered engineer and that the Benchmark commissioning checklist is completed at the time of installation.

Installation information

The installation cost for a Viessmann Vitodens 100-W is typically around £1,200. However, it’s important to remember that no two homes are the same, and your final price will depend on a few key factors. If you’re doing a straightforward swap in the same location with minimal pipework changes, costs stay on the lower end. If your engineer needs to relocate the boiler, upgrade old pipework to meet current Gas Safe standards, or navigate a tricky flue position through a roof, the labour time and the price will naturally increase.

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 fit a magnetic filter when installing a new boiler. A system flush isn’t legally required, but it’s strongly recommended if you’re replacing an older boiler, and many manufacturers (including Viessmann) make it a condition of their extended warranty.

A flush removes “sludge” (iron oxide and other debris) that has built up over the years in your radiators and pipework. To keep your new Vitodens 100-W running smoothly and protect that valuable 10-year heat exchanger warranty, your installer must also fit an in-line magnetic filter. This device catches any future debris before it can reach your boiler’s internal components.

As standard, a system flush will cost between £350 and £800, whilst a magnetic filter can cost anywhere from £65 to £300 depending on the model. Some installers include these costs in their overall quote, whilst others list them separately, so be sure to clarify this when comparing quotes.

Finding a Gas Safe registered engineer

All installers must be Gas Safe registered by law, but choosing an engineer with specific Viessmann training is the best way to ensure your 30-day registration window is handled correctly, your extended warranty is fully protected, and the boiler is set up to run at optimal efficiency.

You can also use the WhatPrice quote service to be matched with vetted, Gas Safe registered installers in your area who have experience with Viessmann products. 

Reviews and ratings

Viessmann holds a rating of 4.4 out of 5 stars on Trustpilot in the UK. Their score reflects a very high level of consistent quality across their product range.

We’ve collated reviews specifically relating to the Viessmann Vitodens 100-W combi, and the feedback reveals a few consistent themes that emerge after homeowners have lived with the boiler for a year or two. Here’s what you can realistically expect:

Positive reviews

Quiet operation is the most frequently mentioned benefit. Reviewers consistently note the boiler is barely audible during operation, even when installed in kitchen cupboards. The difference compared to older boilers is particularly striking, with radiators heating up noticeably faster than previous models.

The 12-year warranty provides genuine reassurance. Multiple reviews highlight this as a key reason for choosing the 100-W over competitors with shorter standard warranty periods.

Long-term reliability features prominently. Several reviewers report having their previous 100-W for five plus years without issues, with some units lasting 12 years before replacement. This track record gives confidence to buyers choosing the same model again when upgrading.

Build quality and the 10:1 modulation ratio are mentioned by reviewers who researched before purchasing, citing these as deciding factors alongside the stainless steel heat exchanger.

Users also praise Viessmann engineers highly for quick and efficient responses when problems do arise with their boilers, 

Negative reviews

The most significant issue concerns installation quality rather than the boiler itself. Multiple reviews report problems traced back to poor installation work, including noisy operation and reliability issues that disappeared once installation faults were corrected. In one case, an installer had accidentally drilled through pipework during floorboard replacement, causing issues that initially appeared to be boiler faults.

Some reviewers note that engineer availability during peak winter can take several days in some regions, though service quality is excellent when they arrive.

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

How the Viessmann Vitodens 100-W combi compares

To help you see where your money is going, here is how the 100-W stacks up against its two most relevant competitors: the Viessmann Vitodens 050-W (the entry-level option from the same manufacturer) and the Alpha E-Tec Plus NX (a popular mid-range alternative).

Below is a comparison to help highlight how the Viessmann Vitodens 100-W compares:

Viessmann Vitodens 100-W combi Comparison Table
Model	Viessmann Vitodens 100-W combi	Viessmann Vitodens 050-W Combi	Alpha E-Tec Plus NX Combi
Typical unit price	£1,400	£1,150	£1,070
Heat exchanger	Stainless steel	Stainless steel	Stainless steel
Standard warranty	5-7 years	7 years	10 Years
Max warranty	10-12 years	10 years	13 years
Built-in WiFi	Yes	Yes	Optional extra
App control	ViCare	ViCare	Alpha Connect
Cupboard fit?	Yes (700mm high)	Yes (700mm high)	Yes (712mm high)
Max output/bathrooms	35kW 2 bathrooms	35kW 2 bathrooms	38kW 2-3 bathrooms

Final thoughts – is the Viessmann Vitodens 100-W combi right for you?

The Vitodens 100-W represents a genuine step up from entry-level alternatives, with engineering features that help maximise its lifespan. If you’re weighing up whether to spend £250-350 more than the 050-W, it’s worth understanding what that price actually buys you.

Unlike many rivals that use aluminium heat exchangers or charge extra for smart controls, the 100-W includes the stainless steel Inox-Radial heat exchanger and built-in WiFi as standard. The stainless steel construction is particularly valuable in hard water areas. The separate 10-year heat exchanger warranty provides reassurance that the most critical component is protected.

The 10:1 modulation ratio differentiates the 100-W from cheaper alternatives. It translates into noticeably quieter operation, smoother heating, and less component wear. The boiler can reduce output to just 10% of maximum capacity, running continuously at low power rather than cycling on and off repeatedly. Over a decade, this smoother operation means fewer stress cycles and marginally lower running costs.

Against the 050-W, you’re paying £250-280 more for improved modulation (10:1 vs 1:8) and extended warranties. Compared with the Alpha E-Tec Plus NX, the Viessmann costs £300-360 more but offers significantly better modulation technology. The Alpha provides better value on standard warranty length (starting at 10- years) and purchase price and also comes with a stainless steel heat exchanger, but doesn’t have the advanced modulation that makes the 100-W a great day-to-day performer.

The 100-W suits medium-sized homes (3-4 bedrooms) with one to two bathrooms where occupants value quiet operation and appreciate the reassurance of that separate 10-year heat exchanger warranty. It’s less suitable for properties with three or more heavily-used bathrooms (where a system boiler would be more appropriate), or for homeowners where budget is the absolute priority and upfront cost matters more than long-term performance.

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