Which best boilers combi condensing?

What is a combi boiler?

Combination boiler or combi boilers are the most commonly used type of boilers which are very famous in UK for a reason. Unlike the system and conventional boilers which requires a hot storage cylinder, the combination boiler comes as an all in one unit which produces hot water for taps and central heating. Not only this, it saves a great space in your homes and its installation is easy and faster comparative to any other boiler.

It usually takes the water from the main supply and provides stronger water pressure. It delivers plenty of hot water. Thus, no longer waits for the tank to refill again and again.

Modern high efficiency unit boilers are the stainless steel condensing boilers with its built-in heat exchanger to provide hot water to a home or a building. During the cold season, usage of combi boiler increases as it provides hot water for heating the surfaces. Therefore, in hot summer days, combi boiler works as per the domestic hot water requirement.

The two main reasons behind the combi boilers great and powerful efficiency is that, these units have high operating efficiency and low internal water volume. This means when in summer days you don’t need space heating you are only paying for the heat of hot water which is domestically required.

What is a condensing boiler?

Majority of new generation combi boilers are condensing boilers. Earlier in the non- condensing boilers, Flue Gas Heat System was not installed. In past any boiler which works, produces flue gases and heat and the produced gas and heat gets wasted in these non-condensing boilers.

A Flue Gas Heat System captures the heat from these flue gases and recycles it to preheat the new cold water as it enters to the boiler from mains. Therefore, this saves lot of energy as the boiler doesn’t need to work again and again to heat the water.

Condensing boilers have become a common alternative to non-condensing boilers in boilers marketplace. Condensing boilers work with high-temperature systems, still more efficient than any other boiler. Condensing boiler efficiency multiplies when used with lower water temperature.

Now you might be thinking which best boilers combi condensing?

Here are top three best combi condensing boilers with all their specifications and features.

Worcester Bosch Greenstar 25i

This is one of the best-selling combi boiler from one of the leading brand Worcester Bosch. This brand has become a household name for their continuous manufacturing of up-to-date boilers.


This Greenstar 25i Boiler manufactured by Worcester Bosch has a high ErP(Energy related product) with the rating of 93% efficiency rate. It is the perfect successor for 24i junior. These wall mounted boilers are designed for the apartments or flats having 1 or 2 bedrooms with 1 bathroom. Although it looks very similar to the other combi boilers of Worcester Bosch but its new magnetic flap opens to reveal the brand new layout. This unit includes increased outputs, higher hot water flow rates, a user friendly control panel and a larger condensate siphon that eliminates the risk of condensate freezing.

This new model has been designed to make installation and commissioning easier and quicker than before. Whereas the unique wall mounting feature enables the installer quick pre-plumb all the seven pipe connections without the boiler being on the wall.

The 25i feature retains the fantastic features of 24i with the added benefits and features. This boiler can fit into a standard kitchen cupboard so that it couldn’t take much of space. Central heating flow and hot water can be adjusted using simple control knobs and the clear information can display. 


User friendly control – There is an immense variety of controls to choose from, range from mechanical to smart options. You will surely expect the control panel once you have opened the flap on the Greenstar 25i. The most amazing thing about the control of this unit is that you can manage your heating and hot water from your smartphone app, isn’t it amazing?

Eliminates condensate freezing – This unit has been tested under stimulated under extreme weather condition and proved its effectiveness in preventing frozen condensate at -15 degree Celsius for a sustained period of 48 hours.

Efficient – the Worcester Greenstar Bosch 25i lives up to its name as a “green” boiler. With the highest ErP(Energy related Product) of 93% this is high performance boiler. Also you will save money on those monthly energy bills.

Warranty – Worcester bosch offers standard warranty of 5 years free of cost to every user.

Weather compensation option – The Greenstar 25i comes up with a weather compensation sensor that has been built to outlast all weather conditions and mark an addition to the efficiency level of the product that has already touched the grounds.


Boiler depth – 330 mm

Boiler height – 710mm

Boiler width – 440mm

Display type – LCD

Power output – 25kW

Fuel type – Natural Gas

Warranty – 5 years

Flow rate – 12.3


In conclusion, the Worcester Bosch Greenstar 25i combi boiler is the perfect choice for a flat having 1-2 bedrooms and 1 bathroom. With one of the highest efficiency this boiler stands out with its high performance.

The Greenstar boiler has won the prestigious Which? Best Buy award for 7 continuous years which simply signifies the quality of the company’s product. With lots of benefits and improvement this Greenstar 25i is the successor for Greenstar 24i model.

Greenstar Highflow 440CDi Floor Standing Combi boiler

The Greenstar Highflow 440CDi Floor standing boiler is the new and exclusive range of Worcester and has been developed for larger two bathroom properties.


The Worcester Greenstar Highflow 440CDi floor standing combi boiler has been designed for the properties with large number of radiators and high demand for instant hot water. The higher outputs of this unit make it suitable for larger properties with multiple bathrooms.

This Greenstar combination gas boiler is SEDBUK band A rated gas boiler and also offers range of unique features that allow easier and quicker installation of the boiler. Also the operating features of wall-mounted combis can be used for mechanical, digital, wireless and new-generation intelligent controls. The Worcester combi boiler now comes with a unique 4.5 meters condensate pump that is fitted as standard.

Now you can control the both hot water and heating temperature as it offers 180l domestic hot water at an average of 35 degrees C rise at flow rates up to 25l/min. Isn’t it great? This unit offers the widest choice of operating features with the ultimate user convenience, performance and fuel economy. This boiler is highly recommended by the Energy saving Trust as well.


Hot water performance – the Greenstar Highflow 440CDi combi boilers are well known for their industry leading hot water flow rates up to 25litres per minute. Without the need for a separated storage tank, this unit is able to deliver comparable flow rates to systems. As a result the tank can refill immediately and showers can be taken for longer period of time. Its separate plate heat exchanger and thermal store ensures the instant availability of hot water to its user.

Clean burning combustion – the Worcester WB5 heat exchanger has been designed and developed to optimize clean burning combustion over an extra area. Each heat exchanger has been tested so, as the gas inlet pressure is correct. The heat exchanger requires minimal servicing i.e. can work for a longtime. It can be cleaned in-situ with an inspection hatch, therefore saves time during the service.

Customized controls- a choice of optional controls is offered by the Greenstar Highflow 440CDi combi boiler to select the type of control which best suits its user requirements. The choice ranges from a simple-to-operate digital programmer, to sophisticated wireless programmer. Also, the  room thermostat and intelligent controls  includes Wave smart control as well.

Premium quality – every Greenstar Highflow CDi boiler is operationally tested before it leaves the factory as a part of Worcester’s quality performance.

Efficient – the Worcester combination boiler is very much efficient as it is SEDBUK BAND A rated boiler. Also it is fully ErP(Energy related product) compliant with 92% rate of efficiency.

Fluing Option – this combination boiler has a full range of condensfit flue options in both 60/100 mm and 80/125mm diameters and includes a plume defector as standard. This versatile flue system can be moved horizontally as well as vertically. Also this multi-directional fluing allows the boiler to be sited in a wider variety of places. 


Boiler height – 850mm

Boiler depth – 600mm

Boiler width – 600mm

Boiler weight – 66.0kg

Warranty – 5 years

Flow rate – 20l/min

Power output – 29kW

Fuel used – Natural Gas


This Greenstar Highflow 440CDi has been manufactured from one of leading boilers company Worcester which has always stood up to the expectations of its customers with user friendly features and variety of additions. This Greenstar combi boiler is the best choice for the people who have 2-3 bedrooms and 2 bathroom house.

With its unique features and free-standing model it is one of the most recommended boiler for semi-detached houses. Even, Energy Savings Trust also recommends this boiler which means you will be doing your part to save the environment with the purchase of this free-standing combi boiler.

Vaillant ecoTEC 835 combination boiler

Attaractive in design and quiet in operation, this boiler delivers superb performance using Vaillant AquaComfort system. This Vaillant ecoTEC combination boiler is suitable for large properties.


The Vaillant ecoTEC 835 combination boiler is a choice for all the large properties due to the increased flow rate and output. The Vaillant is Europe’s second largest boiler manufacture. It offers high quality and polished energy products.

Requiring no hot water cylinder and water tank in the loft, this combination boiler by Vaillant provides you almost instant hot water supply to your taps and can fit into any corner of your house with limited space. Vaillant combi boilers are highly efficient and deliver a top SEDBUK Band ‘A’ rated fuel efficiency and powerful DHW performance. It offers premim components for outstanding performance, quality and the best heating to your homes. This boiler has an ERP rating A, also it comes with frost protection, keeping it protected from wintery days.

It’s innovative new flame lit detection system will help you to monitor the low combustion and noise with optimized burner settings. Also it comes with assured comfort that there is a back-up mode so in case of a fault with the combustion boiler, it will able to revert to the last known operating system.


User-friendly controls – alike every other combi boiler, this boiler also has the control panel behind the flap which allows you to do the normal switch on/off. Whereas the digital display will remind you of any fault so that it could be easy for the engineers to diagnose what’s the fault in the boiler. Controlling and regulating hot water temperature will be on your tips as you can manage the settings through your smart phones because of smart and techy thermostats.

Efficient- the ecoTEC plus 838 combi boiler is a ‘A’ rated brand with an ErP(Energy related Product) of 89.3%. With its superb performance, it will reduce the amount of energy wasted and thus reduces the carbon footprint. The outstanding performance will surely help you in saving your energy bills.

New flame lit detection system – the burner is automatically monitored to ensure the minimal combustion and noise and have a back-up so in the fault, combustion boiler will get back to the previous options. This is all done by the innovative new flame lit detection system.

Reliable – this boiler is reliable as it comes with frost protection, keeping it protected from cold days. This boiler has high level of technology that are made to keep a check within every 30 seconds to make sure that there is low combustion and eliminate the for the users to check and maintain the carbon dioxide level as well.

Warranty – this Vaillant ecoTEC plus boiler provides you 5 year standard warranty which can be extended up to 7 years if you install it frm Vaillant Advance installer.


Boiler height – 720mm

Boiler depth – 372mm

Boiler width – 440mm

Boiler weight – 38kg

Warranty – 5 years

Flow rate – 14.3l/min

Power output – 35kW

Fuel used – Natural Gas


The Vaillant ecoTEC 835 is an excellent choice if you are searching for bigger properties. This range is highly efficient and reliable ehich helps in reducing the carbon prints. Th ecoTEC plus boiler has been awarded Quiet Mark status for low noise and output.

Whereas its astonishing design will surely make you purchase it for your place.

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