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Last updated: 3rd April, 2024


Worcester Bosch Greenstar CDi Compact Combi Review

Worcester Bosch Greenstar CDi Compact Combi Review

One of the most popular compact combi boilers on the market, here we take an in depth look at the main talking points and key features of the Worcester Bosch Greenstar CDi compact.

Worcester Bosch Boilers

As one of the world's leading names in heating innovation, Worcester Bosch, founded in 1962, is synonymous with customer satisfaction.

Blending high end technology with assured traditional engineering, has made the brand one of Europe's most trusted boiler manufacturers.

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Worcester Bosch Greenstar CDi Compact

At iHeat, we stock a wide range of Worcester boilers. However, today we're going to be talking about the popular Greenstar CDi compact model. One of the best compact boilers on the market.

The Worcester Bosch Greenstar CDi Compact has been created to follow the form of the extremely popular original Greenstar branch of the Worcester Bosch range.

Combining the latest in heating design and energy efficient application, the Greenstar hallmark represents a modern icon of the boiler industry.

The versatile Greenstar CDi compact comes in three available kW outputs and flow rates:

kW (kilowatt) Output Size

Flow Rate - l/min (litres per minute)


11.4 l/min


13.1 l/min


14.7 l/min

Greenstar CDi Compact Spec

Efficiency rating


Energy efficiency class

A rated


Wall mounted




680mm (Height) x 390 (Width) x 280mm (Depth)

Get an instant free quote and fixed price on the Greenstar CDi compact range today here at iHeat.

Greenstar CDi Compact Review

Greenstar CDi Compact Key Features

Energy Efficiency

The Greenstar CDi compact has an A rated ErP score with a 93% efficiency rating. An energy efficient new boiler can significantly reduce an owner’s energy bills, with an A rated boiler considerably helping homeowners save money compared to an old boiler or antiquated system.

Built In Frost Protection

Cold weather complications account for a huge number of boiler unreliability or breakdown issues, this often results in service or repair fees.

The Greenstar CDi compact releases condensed flue gases via a CondenseSure siphon, in cyclical bursts to reduce blockages stemming from a frozen condensate pipe.

Compact Size

The smallest model in the CDi range, the sleek design of the compact means it can be easily wall mounted or fit into a standard kitchen cupboard.

The CDi compact is ideally suited to heat small properties but does have the power outage and flow rate in its 36kW capacity to sufficiently heat a medium sized home.

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Combi Boiler

Benefits Of Combi Boilers

Combi boilers are a popular choice for a number of reasons. Unlike conventional boilers, combi (combination) boilers link a home’s central heating system and water heating; no separate hot water tank is needed which is cleaner as it avoids potential rust or debris build up.

This allows a compact boiler which could fit into a standard kitchen cupboard or be wall mounted, to thoroughly heat a home without stealing lots of space.

Combi systems are also easier to service or for boiler replacement due to their popularity, meaning greater availability.

CDi Compact A Rated

Aluminium Heat Exchanger

The CDi compact comes as standard, as do all Worcester Bosch boilers, with an aluminium heat exchanger.

Although initially efficient, aluminium is far more susceptible to corrosion compared to stainless steel heat exchangers. Heat exchangers can become faulty over time, but this is a relatively simple fix.

Smart Thermostat

The Greenstar CDi compact is fully compatible with smart thermostats like the Worcester Bosch easy control system.

This means thanks to the brainy bunch who manufactured your new boiler, it can be easily controlled at the touch of a button for rapid regulation and optimisation.

Worcester Bosch Greenstar CDi Compact Price

The price of the Greenstar CDi compact varies on the output you require, the higher the kW output, the more the initial boiler unit cost.

iHeat offers prices ranging from £2190-£2690 on the CDi compact range, this includes free next day installation by a Gas Safe registered engineer.

Should You Buy A New Worcester Bosch Greenstar CDi Compact Boiler?

Overall the CDi compact is a great choice for a new central heating and hot water system.

A lightweight unit, that is both space saving and highly efficient, making it a perfect fusion of design and application for small or medium sized properties.

Providing a substantial heat output for this size boiler, the CDi compact combi definitely provides a healthy cost value from a trusted UK brand. 

Get an instant free quote and fixed price on the Greenstar CDi compact range today here at iHeat

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iHeat New Boiler Costs

Boilers can be a daunting purchase for many people as they’re an appliance with a lot of responsibility, providing heat for you and your family is something you want to get right. Boilers aren’t exactly a quickly disposable item either, potentially lasting you a decade.

Effectively, new boiler cost can be split into two segments: the first is the actual boiler itself (unit price), and the second is the cost of the boiler being installed (set up) in your property by an expert engineer. 

Here at iHeat, we want to remove all of this undue stress and make the decision making process of upgrading to a new central heating system, as easy as possible.

Boiler costs can vary depending on a number of factors including their brand, model, fuel, output, warranty, labour and installation type. Typically a new boiler will cost between £1,845 and £3,500, below is a list of average boiler installations offered by iHeat (guide only).

Installation Type

Price (inc VAT)

Combi to combi swap


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System to combi conversion


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New boiler install


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Back boiler to a combi


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System to system


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Frequently Asked Questions

How Efficient is the Greenstar CDi Compact?

The Worcester Greenstar CDi Compact is known for its high efficiency, boasting an ErP (Energy related Products Directive) rating of 'A' for both heating and hot water. These boilers are designed to operate efficiently, helping to reduce energy consumption and lower heating bills. Their high-efficiency rating is a result of advanced engineering, including features like condensing technology that recovers heat that would otherwise be lost.

What Size is the Worcester CDi Compact?

The Worcester Greenstar CDi Compact series includes boilers that are designed to be space-saving and easily fit into standard kitchen cupboards. Although exact dimensions can vary by specific model within the series, a typical size for these compact boilers is around 690mm (height) x 390mm (width) x 280mm (depth). This makes them an ideal choice for homes with limited space.

What is a CDi Boiler?

A CDi (Compact Disc Interface) boiler, in the context of Worcester Bosch's product line, refers to their range of high-end combi boilers known for compact design and high efficiency. The CDi range is designed to provide both heating and hot water directly from the boiler without the need for additional water tanks or cylinders, making them a popular choice for homes where space is at a premium. They are known for their performance, reliability, and advanced features like programmable controls.

How Do I Reset My Worcester Greenstar SI & CDi Compact Boiler?

To reset a Worcester Greenstar SI or CDi Compact boiler, you typically need to press the reset button on the boiler's control panel. This button is often marked with a circular arrow symbol. Press and hold the reset button for about 2 seconds, and then release. The boiler will attempt to restart. If the boiler does not reset or continues to display a fault, refer to the user manual for troubleshooting or contact a professional engineer.

Why Does My Worcester Boiler Keep Firing Up When Heating is Off?

If your Worcester boiler fires up when the heating is off, it could be due to several reasons. One common cause is the pre-heat function, which keeps a small amount of water hot for instant hot water availability. Other potential reasons include issues with the thermostat, external controls sending incorrect signals, or a need for recalibration or servicing to address a fault within the boiler's operation.

What Happens if I Miss My Boiler Service?

Missing your annual boiler service can lead to several problems, including reduced efficiency and increased energy costs, as minor issues can develop into more significant problems if left unaddressed. Additionally, neglecting regular servicing may invalidate your boiler's warranty, leaving you without coverage for any subsequent faults or breakdowns. To ensure your boiler remains in optimal condition, it's advisable to stick to the recommended servicing schedule.

Stephen Day profile photo
Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.