Worcester Bosch Greenstar CDi Compact Combi Boiler Cost with Installation

The Greenstar CDi Compact is Worcester Bosch’s most compact gas combi, built for properties where available installation space is tight. At 280mm deep and 690mm tall, it is one of the shallowest combis Worcester Bosch produces.

All three output sizes share the same footprint, LPG versions are available across the range, and each model carries a 7-year standard warranty – extendable to 8 years with a Greenstar System Filter, or 10 years with a filter and a Worcester Bosch Accredited installer.

See more of the Worcester Bosch Greenstar CDi Compact combi specifications below:

Worcester Bosch Greenstar CDi Compact Combi Product Table
	Available outputs	28kW	32kW	36kW
	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	7 years
	Max output (kW)	28	32	36
	Flow rate (l/min)	11.4	13.1	14.7
	Mounting	Wall-mounted
	Dimensions (mm)	690 x 390 x 280
	Typical price (incl. VAT)	£1,200	£1,350	£1,450
	Typical installation cost (incl. VAT)	£1,200
	Total cost	£2,400 – £2,650

*Terms and conditions apply.

Worcester Bosch Greenstar CDi Compact Combi overview

The Worcester Bosch Greenstar CDi Compact is a gas combi boiler built for homes where installation space is tight. At 280mm deep, it is one of the slimmest combis Worcester Bosch produces, and all three output sizes share the same footprint, making it a practical choice for cupboard installations.

Despite its compact casing, it delivers solid hot water performance across the range, carries a 7-year standard warranty extendable to 10 years, and is available in LPG across all three outputs – a combination that few rivals at this size can match.

Worcester Bosch Greenstar CDi Compact Combi Range
Model output size	House size	Bathrooms	Radiators
28kW	Flats 1 to 2 bedrooms	1	Up to 10
32kW	Small to medium homes, 3 bedrooms	1 & ensuite	Up to 15
36kW	Medium homes, 3–4 bedrooms	2	Up to 20

Getting the output right matters as much as the boiler itself. The 28kW model delivers 10.0 l/min, which is well-suited to a flat or small home with a single bathroom and moderate hot water demand. Step up to the 32kW and you get 11.9 l/min, enough to handle a three-bedroom home with a bathroom and ensuite without issue. The 36kW reaches 12.9 l/min and is the right choice if two bathrooms are in regular use – though if both are likely to run simultaneously at peak times, a system boiler with a cylinder is the more reliable option.

Key benefits at a glance

• ErP A-rated efficiency (94% efficient)
• Compact cupboard-fit design (just 280mm deep)
• Available in LPG across all three outputs
• PreHeat function for faster hot water delivery
• Front-access servicing so it does not need to be removed from the wall
• Compatible with Worcester Bosch Wave and EasyControl smart controls
• Hydrogen ready
• 7-year standard warranty, 10 years with Accredited installer and System Filter*

Worcester Bosch Greenstar CDi Compact Combi technical specifications

Despite its compact casing, the CDi Compact packs in most of what you would expect from a mid-range Worcester Bosch combi. 

The WB7 aluminium heat exchanger does most of the work, supported by a PreHeat function that reduces wait times at the tap and an ECO mode designed to cut energy use when demand is low. 

Output and efficiency ratings

All three CDi Compact models carry 94% central heating efficiency, ErP A-rated across the range. As condensing boilers, they recover heat from exhaust gases that older non-condensing boilers expelled – which is why homeowners switching from older installations often see reductions in their gas bills within the first few months.

The 94% efficiency figure is consistent across all three output sizes, so choosing a higher-output model does not affect running costs per unit of energy – the difference is purely in hot water delivery capacity.

For homeowners who want to increase efficiency further, adding a Worcester Bosch Wave controller with weather and load compensation upgrades the ErP classification to A+, adjusting the flow temperature based on outdoor conditions rather than running at full output regardless of the weather.

Dimensions 

All three models share dimensions: 690mm tall, 390mm wide, and 280mm deep.

That 280mm depth is the CDi Compact’s defining feature – at this measurement, it fits inside a standard kitchen unit with room to spare, where many rival combis at similar outputs cannot.

The consistent footprint across the 28kW, 32kW, and 36kW models also means pipework can be planned around the same mounting position regardless of which output is chosen, which simplifies installation if you are upgrading within the range.

Components included

The CDi Compact is built around Worcester Bosch’s WB7 aluminium heat exchanger, manufactured using an advanced casting process. Worcester Bosch backs it with a separate 10-year component guarantee, useful cover on the single most critical component in the system.

The PreHeat function keeps a small volume of water pre-heated in the heat exchanger, ready for the next hot water draw. This reduces the time between turning a tap on and receiving hot water, which is a noticeable improvement over boilers with no pre-heat capability.

ECO mode works alongside PreHeat by reducing standby energy use and limiting how long the boiler pre-heats between draws. In practice, this can lengthen the wait time at the tap, which is a source of the negative feedback covered in the reviews section. Disabling ECO mode and running PreHeat as standard is a common resolution, and for most households the energy difference is negligible.

The boiler uses siphonic condensate disposal, with an optional CondenseSure upgrade for installations where the condensate pipe runs through an exposed or unheated space. This is worth raising at the survey stage if your pipe route is external as frozen condensate is one of the more common causes of winter breakdowns across all combi boilers, and CondenseSure is a straightforward preventive measure.

The CDi Compact is also solar compatible and works with the Worcester Bosch Wave and EasyControl thermostats, as well as third-party controls including Hive, Nest, and Tado.

💡TopTip: Adding a Wave with weather and load compensation upgrades the ErP energy class to A+.

Prices and installation costs

The CDi Compact sits in the mid-range of the Worcester Bosch combi lineup – more than entry-level alternatives from Baxi or Glow-worm, but less than the newer Greenstar 8000+.

A standard horizontal side-wall flue is included in our prices – which is a standard part of boiler installation, with the flue directing harmful gases outside. A horizontal flue adds around £100-£150; a vertical roof flue can exceed £500.

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

Worcester Bosch Greenstar CDi Compact Combi Costs
Output size	Unit cost (incl. flue)	Total (incl. installation)
28kW	£1,200	£2,400
32kW	£1,350	£2,550
36kW	£1,450	£2,600

Warranty and support

The CDi Compact’s 7-year standard warranty is one of the stronger baselines in the compact combi class. It is activated by registration within 30 days of installation. 

Fitting a Greenstar System Filter extends the cover to 8 years; fitting a filter and using a Worcester Bosch Accredited installer extends it to 10 years. 

Annual servicing by a Gas Safe registered engineer is a condition of the extended warranty. The WB7 heat exchanger carries a separate 10-year component guarantee.

Worcester Bosch’s own engineer network handles warranty call-outs nationally. The brand consistently receives strong feedback on response times and the use of genuine parts during repairs.

Installation information

A standard like-for-like combi swap typically costs around £1,200 and can be completed in a day. 

The CDi Compact’s pre-plumbing jig means pipework can be run before the boiler arrives, and the front-access design means most servicing and repair work can be carried out without removing the boiler from the wall, which keeps ongoing maintenance costs lower.

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 fitting a Greenstar System Filter also upgrades the standard warranty from 7 to 8 years.

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 the Greenstar System Filter.

Finding a Gas Safe registered engineer

All gas boiler installations must be carried out by a Gas Safe registered engineer. For the 10-year warranty, the installer must hold Worcester Bosch Accredited status.

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

Reviews and ratings

Worcester Bosch holds a 4.6 out of 5 rating on Trustpilot UK, based on over 50,000 reviews. The CDi Compact draws consistent positive feedback: efficiency gains over older boilers; quiet operation; and warranty confidence.

Positive reviews

The 10-year warranty is the most frequently cited reason for choosing the CDi Compact. Owners tend to mention it at the point of purchase and again when the boiler has been running without issue for a year or two, as both a selling point and a source of ongoing reassurance.

Quiet operation is praised consistently, with reviewers who have replaced older Worcester models being struck by the difference, and several mentioning that the bedroom or kitchen location which ruled out their previous boiler was straightforwardly fine with the CDi Compact.

Efficiency improvements after switching from older non-condensing boilers are regularly noted, with reviewers reporting visible reductions in gas bills within the first few months. One reviewer switching like-for-like on output reports roughly 15% lower consumption over the year, though results vary by property and usage.

The compact footprint earns specific praise from homeowners constrained by existing flue positions or worktop heights, with several reusing the original wall penetration and avoiding additional installation work as a result.

Negative reviews

ECO mode performance is the main recurring complaint. Several owners report a long wait for water to reach a usable temperature at the tap, with the supply going hot then cold before settling. One reviewer disabled ECO mode entirely and runs pre-heat as standard, finding it both more practical and less wasteful.

Frustration over warranty terms cropped up in a handful of reviews. A couple of owners discovered after a fault developed that their cover was five rather than ten years – in both cases the failure came shortly after the five-year mark. 

Just Remember: The ten-year cover requires an Accredited installer, a Greenstar System Filter, annual servicing, and registration within 30 days; buyers who do not meet all four conditions at installation will receive shorter cover than they may expect.

A small number of reviews mention pressure loss, with owners finding the filling mechanism fiddly to locate and use. One review describes persistent pipe-transmitted noise that extended correspondence with Worcester Bosch failed to resolve.

How the Worcester Bosch Greenstar CDi Compact Combi compares

Worcester Bosch Greenstar CDi Compact Combi Comparison Table
Model	Worcester Bosch Greenstar CDi Compact combi	Worcester Bosch Greenstar 4000 Combi	Viessmann Vitodens 050-W Combi
Typical unit price	£1,350	£1,200	£1,150
Heat exchanger	Aluminium	Aluminium	Stainless steel
Standard warranty	7 Years	7 Years	7 Years
Max warranty	10 Years	10 Years	10 Years
Built-in WiFi	No	Yes	Yes
App control	Bosch EasyControl	Bosch EasyControl	ViCare
Cupboard fit	Yes	Yes	Yes
Max output/bathrooms	36kW 2 bathrooms	30kW 1 & ensuite bathrooms	35kW 1-2 bathrooms

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

Final thoughts – is the Worcester Bosch Greenstar CDi Compact combi right for you?

The CDi Compact occupies a well-defined niche in the Worcester Bosch range: it is the choice for homeowners who want the Worcester Bosch warranty and installer network, in a unit whose 280mm depth fits tight installations. The consistent Trustpilot feedback on quiet operation and efficiency gains over older boilers makes a strong case for the model on its own terms.

Where the CDi Compact falls slightly short of newer rivals is on connectivity. Neither built-in WiFi nor app control comes as standard, and homeowners who want smart control need to budget for a Wave or EasyControl on top of the boiler price. Competitors at a similar price point, including the Viessmann Vitodens 050-W, include this as standard.

The Worcester Bosch Greenstar 4000 is the most natural choice for most homes – it adds built-in WiFi and Bosch EasyControl as standard, and at £1,200 for the unit it comes in £150 cheaper, though it tops out at 30kW.

The Viessmann Vitodens 050-W undercuts the CDi Compact on price at £1,150, matches it on warranty length, adds built-in WiFi and ViCare app control as standard, and uses a stainless steel heat exchanger rather than aluminium, making it the stronger specification on paper at a lower unit cost. The CDi Compact’s answer to both is the 280mm depth; if that doesn’t apply to your property, the 4000 and the Vitodens 050-W are both worth a close look.

The heat exchanger is aluminium rather than stainless steel – a point that matters more in properties with older, poorly maintained heating systems, where water quality can be harder on internal components. Fitting a Greenstar System Filter (which is also required for the extended warranty) helps protect the boiler from such damage over time, and the separate 10-year component guarantee on the WB7 exchanger reflects Worcester Bosch’s confidence in the part.

For a one-bathroom flat or two-to-three-bedroom home where space is constrained, the 28kW or 32kW CDi Compact is a well-supported, efficiently performing choice with a warranty structure that rewards homeowners who use Accredited installers and keep up with annual servicing. For homes with two bathrooms in regular joint use, the 36kW model is worth considering or a system boiler and cylinder, and a Gas Safe engineer is the right person to make that call.

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