In recent times, energy efficiency has been more paramount than before. Not only does this trend help you reduce your energy bills, but it also significantly helps to conserve the environment. How? Energy efficient boilers, for instance, consume less power and have lower CO2 emissions, reducing both the impact of global warming and your monthly bills.

The exclusive condensing boiler technology has reached new heights in terms of energy efficiency. Today, boilers are lighter, quieter, smaller, and even include next-gen features such as Smart Learning thermostats and Weather Compensation. With these distinct technological advancements, you can now save a lot of the resources you would otherwise spend on energy bills. Boiler manufacturers are creating highly efficient products and as such, if you are looking to invest in a boiler, now is the ideal time!

One of the most popular boiler brands is, of course, the Worcester Bosch brand. Their products have won over the hearts of clients from across the globe and even won various awards for their high quality and efficiency. Here are the top 5 most efficient Worcester boilers.

Worcester Bosch Greenstar 24i

The Greenstar 24i is a unique combination boiler that boasts a reasonable 24kW output rendering it a perfect fit for small to medium properties. With this fantastic invention, you enjoy:

• A large yet comfortable and easy to use boiler control plan

• Several user-friendly controls

• Highly efficient pump

• Instant hot water

• 5-year guarantee

• Heating and hot water rating

Worcester 25i Boiler

This is a direct replacement of the remarkably popular Worcester 24i Junior boiler. The Worcester 25i Greenstar is a combi boiler designed to suit small properties. It can service one bathroom and three bedrooms comfortably. Despite its similarity to the former, it comes with a new magnetic flap that opens to reveal an outstandingly new layout. With a new digital display, this boiler is also compatible with the assortment of Worcester Comfort controls and the Wave.

What’s more, you can be confident of its efficiency as this product fully complies with the new ERP Directives as well as guaranteeing similar performance to that of the 25Si Compact.


• SEDBUK A-rated (over 90% efficiency levels)

• Compact dimensions

• ERP compliance

• Hot water and central heating temperature control

• Increased efficiency in standby mode (3.5 watts)

• Wall mounting frame that enables you to conceal pipework from public view

• Inbuilt CondenseSure Siphon

• Vertical pre-piping kit

• Multi-directional flue options

• Lowest CO2 and NOx emission levels

Worcester Greenstar 25Si Combi Gas Boiler

Next on the list is the Worcester Greenstar 25Si, which boasts a central 24kW heating output. It is a perfect central and hot water heating solution with the ability to service smaller properties extending to a single bedroom and three bathrooms.

What is perhaps its most remarkable feature besides its outstanding efficiency rate is its size. Its compact dimensions make this the smallest Worcester combi boiler ever! What’s more, the Greenstar 25Si offers you exceptional performance levels and reliability, as with all Worcester products.

Boasting a SEDBUK A-Rating, this boiler can quickly achieve a remarkable efficiency rate of well above 90%. This way you can significantly reduce your energy bill.


• SEDBUK A-Rated (90.5% efficient)

• Compact dimensions

• Jig and 7 pre-plumb connections that allow quick installation

• Inbuilt LCD for fault diagnosis and current operation status

• 5-year warranty

• Lightweight (32.9kg)

• EMS-BUS compatibility

Worcester Greenstar 12Ri Compact Regular Boiler

If you are looking for an efficient regular boiler with the capacity to effectively service your hot water and low heating demands, then the Greenstar 12Ri boiler is your best choice. Nonetheless, regular boilers offer central heating only so you need to install a hot water cylinder within the system to facilitate hot water provision.

It is built using a unique condensing technology which can effectively reduce your hot water and heating bills by between 15 and 20% annually; and if you are changing up from a much older G-rated boiler, the efficiency levels get even better at 30%. Imagine that!


• Over 90% efficient (SEDBUK A-Rating)

• Light – 22.6Kg

• Reversible return and flow pipes

• Flexible installation courtesy of compact dimensions

• Warranty: 5 years

Worcester Greenstar 15i System Boiler

It would be an injustice to complete this list without including yet another amazing product – the Greenstar 15i boiler. This boiler is ideal for small properties like bungalows and flats.

It offers A-rated efficiency, compact dimensions, and low-lift weight allowing you to effectually save a lump sum on your annual heating expenses while still delivering great reliability, even under the coldest conditions. Its high efficiency can reduce your annual heating bills by between 15 and 20% annually, with an even higher figure if you are replacing the traditional G-rated boilers.


• 700mm h x 330mm d x 400mm w

• Pump and integrated expansion vessel

• SEDBUKA A-rated (90.1% efficient)

• A low-lift weight of 25kg

• Compact dimensions allowing flexible installation

• 5-year warranty


All these five Worcester boilers are high-performance appliances which would effectively help you save a significant amount of the money that you spend on your annual energy costs. They are a worthwhile investment. Nonetheless, just like with all other decisions, it all comes down to your individual preference when picking out the best one for you.