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Worcester Bosch Greenstar 30Si Compact Combi Boiler – Review

Worcester Bosch’s combi boilers have become a popular name amongst UK households. Founded in 1962, Worcester Bosch has been at the top of their game now for almost five decades manufacturing boilers, as well as other energy goods.

Today we’ll be reviewing the Greenstar 30Si Compact combi boiler – a more compact alternative to the popular Worcester Bosch 30i. If you’d prefer to have your combination boiler fitted in a standard-sized kitchen cupboard, then this boiler is the best choice for you.

Will the Worcester Bosch Greenstar 30Si Compact be suitable for my home?

The Greenstar 30Si boasts a heating output of 24kW and a hot water output of 30kW. The 30Si is also an ideal fit for small to medium-sized homes with one bathroom, as well as being great for tight spaces if you’d like to fit the boiler in a utility or kitchen cupboard. The flow rate works at around 12.3 litres per minute, which is suitable for your kitchen/bathroom taps and one to two bathrooms with a shower or bath installed in one of them.


The 30Si Compact offers the same standard combi boiler controls that you’d expect with most other boilers available on today’s market. With an on/off switch, temperature settings, and an LED for faults; you’re pretty much set regarding onboard controls out of the box.

Worcester Bosch also offers programmable and smart thermostat options, which will give you better control of your boiler rather than manually changing the onboard settings. If programmable or smart thermostats aren’t your cup of tea, you may want to go for a mechanical room thermostat to set temperatures. Although, please be aware that you won’t be able to accurately change your home’s temperature settings, which means you’ll risk wasting energy unnecessarily. To ensure full control of your combination boiler, we recommend the Greenstar Comfort thermostat, a programmable thermostat which allows you to set temperatures and schedule your heating and hot water with ease. Alternatively, if you’d prefer to modernise your central heating system, Worcester Bosch’s entry into the smart thermostat market, the Wave, will enable you to control your heating from your smartphone or tablet.

The Wave, a lot like the Nest, is a self-learning device, which alters your heating schedules based on your temperature settings and schedule. If you decide to install a smart thermostat, you’ll see an improvement in your energy usage (lower energy bills) and better energy efficiency. The extra control over your central heating is a huge plus side to the Wave.


Coming in at 690x390x280mm, the 30Si is an excellent fit for kitchen cupboards if you’re tight for space. Since combi boilers use mains fed water, you’ll benefit from the lack of tank or hot water cylinder. It’s important to check if your property is suitable for a combi boiler as sufficient mains pressure is a requirement for a combination boiler to be installed. We will able to test this for you.


Worcester Bosch offers a standard 5-year standard warranty with each of their Greenstar boilers, although this can changed to a further 5 years if a Worcester Accredited Installer performs the installation. With Hometree, you could benefit from extra peace of mind with a 5-year warranty with each of our boilers that can be extended to 10 years.

Energy Efficiency

The Greenstar 30Si is a “green” boiler. The 30Si boasts an energy efficiency rating, also known as ErP, of 94% (an A Grade), so you can expect to start to save money on your energy bills while also reducing your carbon footprint. It’s essential to have a high-rated boiler installed in your home fight rising energy prices and reduce costs.

The ErP Directive ensures that all energy products are tested for performance and efficiency before they appear on the market. Each product will need to pass specific criteria to reach the highest level of efficiency. If the ErP isn’t happy with a product, the manufacturer will 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 30Si Compact certainly packs a punch for its smaller size. It’s an ideal fit for small to mid-sized properties, which includes homes with two bathrooms bathroom and up to 3 bedrooms. With high-efficiency levels and excellent performance, it isn’t a surprise that the Greenstar boiler range has won the Which? Best Buy award for 7 years running, which is a great sign of quality from the Worcester Bosch brand. You can be assured that breakdowns are highly unlikely and you will see a saving on your energy bills from the moment your boiler is up and running.

 Worcester Bosch Greenstar 30Si Compact
ErP rating (energy efficiency)A (89.3%)
Size (HxWxD in mm)690x390x280
Heating output (kW)24
How water output (kW)30
Flow rate (litres/min)12.3
Standard warranty (years)5 (extended warranties available)
Other available sizes (kW)25

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 30Si 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 30Si Compact combi boiler manual

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