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Worcester Bosch Greenstar 28CDi Compact Combi Boiler – Review

Founded in 1962, Worcester Bosch is a popular choice in the UK’s boiler market after almost five decades manufacturing energy goods. Worcester Bosch’s range of high quality and efficient combination boilers have become a household name on a national scale.

In this review, we’ll be taking a closer look at the Greenstar 28CDi Compact combi boiler, the perfect fit for a standard kitchen cupboard due to its small size and high outputs.

Will the Worcester Bosch Greenstar 28CDi Compact be suitable for my home?

The 28CDi offers a heating output of 24kW and a domestic hot water output of 28kW. If you’re worried about giving up space in your home for a new boiler, the 28CDi has been designed to fit into kitchen cupboards. The flow rate for this boiler is 11.4 litres per minute, which is suitable for homes with up to two bathrooms (with a shower installed) and up to 3 bedrooms.


Out of the box, you get the usual standard boiler controls installed on the control panel of the Worcester Bosch 28CDi Compact. The onboard controls include an on/off switch, temperature settings, and an LED for faults.

Rather than settling with standard boiler controls, Worcester Bosch offers a range of controls from programmable to smart thermostat. Both programmable and smart thermostats provide the option to schedule your heating and hot water, as well as temperature changes. If you’d prefer to change your home’s temperature without scheduling, a mechanical room thermostat is also an option, although you may risk wasting energy and the temperature settings could be inaccurate. It’s essential to have full (and precise) control of your boiler, which is why we recommend the Greenstar Comfort thermostat if you want to venture down the programmable thermostat route. If a smart thermostat is on your list and you’d like to update your central heating system, Worcester Bosch’s smart thermostat, the Wave, allows you to control your heating and set schedules from your smartphone.

The Wave, a lot like the Nest, is a self-learning device, which alters your heating schedules based on your temperature settings and schedule. With the installation of a smart thermostat, you would see an improvement in your energy usage (in the form of lower bills) and enhanced energy efficiency. The extra level of control is a huge plus side to the Wave.


Coming in at 690x390x280mm, the 28CDi Compact is designed to fit perfectly within a standard kitchen cupboard, which is great if you’re running low on space. Combi boilers are mains-fed which eliminates the need for a loft-installed tank or hot water cylinder. We’ll be able to check if a combi boiler is suitable for your home and if you have sufficient mains water pressure.


Worcester Bosch offers a 5-year standard warranty with their range of Greenstar boilers. At Hometree, we offer a 5-year warranty with each boiler for your peace of mind. We also offer a 10-year warranty for an extra charge with our boiler installations.

Energy Efficiency

The Greenstar 28CDi Compact lives up to it’s “green” name with a high ErP rating of 92% (an A grade). With a highly efficiently boiler, you can expect to make a saving on your energy bills and increased performance out of the box. Reducing your carbon footprint and combatting energy prices is also necessary with a new boiler.

The ErP Directive actively tests all energy products to ensure that they are performing to the highest standard before they appear on the market. If a product fails to meet the criteria set by the ErP, the manufacturer would need to take the necessary steps to update the product and bring it up to a satisfactory rating. You can read more about the ErP Directive here.


The Greenstar 28CDi Compact is a high-performance boiler with high efficiency and the perfect fit for small to mid-sized homes (1 to 3 bedrooms and up to 2 bathrooms). The Greenstar boiler range has won the Which? Best Buy award for 7 years in a row, which goes to show that the Greenstar CDi range is a popular choice among customers. Breakdowns are highly unlikely with Worcester boilers, and you would see a saving on your energy bills from the moment your boiler is on the wall.

 Worcester Bosch Greenstar 28CDi Compact
ErP rating (energy efficiency)A (92%)
Size (HxWxD in mm)690x390x280
Heating output (kW)24
How water output (kW)28
Flow rate (litres/min)11.4
Standard warranty (years)5 (extended warranties available)
Other available sizes (kW)32, 36

Which? boiler review

The consumer group Which? review each boiler on the market to find the most (and least) reliable boilers according to a survey completed by thousands of boiler owners. In each review, Which? supply a brand score percentage and star ratings for each category. Take a look at the Worcester Bosch Greenstar 28CDi Compact ratings below:

Which? Score 
Efficiency rating★★★★★
Brand reliability★★★★★
Brand customer score★★★★★
Ease of repair★★☆☆☆
Ease of service★★★☆☆
Availability of parts and spares★★★★★
Build quality★★★★★
Engineer recommendation★★★★★
Brand score86%

Boiler manual

Worcester Bosch Greenstar 28CDi Compact combi boiler manual

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