Best Combi Boiler in the UK: Expert Picks 2025

Worcester Bosch Greenstar Heatslave II comes in three outputs: 12/18kW, 18/25kW and 25/32kW. This makes it the best combi boiler for a 3 bed house and even larger properties that aren't connected to the gas grid. It allows for a flow rate of up to 22 litres per minute, which suits properties with multiple bathrooms. 

These Worcester Bosch boilers are equipped with the next-generation Heatronic 4i digital control unit. It allows homeowners to set the preferred home temperature to prevent overheating and save on energy bills. Its Eco Hot Water mode takes the energy consumption reduction even further by heating the water in 10-12 seconds after you open the tap. 

Yet it's worth noting that some combi boiler reviews pointed out that this boiler produces "almost boiling" hot water, even after setting the hot water temperature to a minimum setting. Also, installing this boiler requires preparing a base for the oil tank, digging a trench for the oil pipe and additional pipework, which might add to your combi boiler installation total. 

This is why consulting with a professional boiler installer is crucial when sifting through the available combi boiler options. They can recommend the best combi boiler option for your particular situation as well as inform on the required pipework and projected installation cost. 

We can help you obtain up to 3 quotes from reputable installers near you without spending hours on research. Simply answer a few questions about your home, and we'll take it from there.

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When searching for an affordable boiler, you should never sacrifice quality. Modern combi boiler manufacturers invest heavily in research and technology to improve longevity, energy efficiency, and boiler reliability. Intergas Eco RF is the best-rated combi boiler when it comes to reliability. 

Intergas developed a unique bi-thermic (two-in-one) heat exchanger design for its boilers. This design simplifies the heat exchanger system by eliminating the need for failure-prone components such as diverter valves, auto air vents, and secondary hot water exchangers.

Eco RF features 12 components and 4 moving parts (compared to 20-30 individual components and 12-15 moving parts in average combi boilers), reducing the risk of wear and tear. The model's Wilo pumps half the boiler's electricity consumption, and its vacuum panel insulation reduces heat and energy losses.

This boiler series comes with a wide output range, with the 36 model being the biggest. Thus, if you're looking for the best boiler for a large 5-bedroom house, Intergas Eco RF 30 and 36 solutions can easily cater to your heating needs. 

Homeowners who search for the lowest, and often seen as the best price for combi boilers, should understand that focusing only on the initial cost isn't the most economical choice in the long run. 

High efficiency ratings, stainless steel heat exchangers, modulating burners, and weather or load compensation features make affordable boilers cheaper to run in the long term.

The compact design of Baxi boilers of this range eliminates the need to modify existing space, being able to fit in a 290mm deep cupboard. Built-in pipes behind the facility allow pipework to be hidden within the boiler casing, making them the best 24kW combi boiler option for spaces where aesthetics is key.  

Also, it caters to a wider range of properties as it can be manually converted between natural gas and LPG without requiring a conversion kit. 

Its Easy-Fill permanent filling ink and external analogue pressure gauge enable users to top up system pressure themselves. Brass hydraulics and a stainless steel heat exchanger extend the boiler's lifespan. 

On top of that, when paired with Baxi's uSense 2 smart thermostat, this model allows for significant savings on heating bills as it optimises energy usage. 

Other brands such as Vokera, Worcester Bosch, Navien, Alpha, and Ideal boilers are constantly regarded as the best combi boilers under £1,000 in the UK. 

To find the best combi boiler on the market at an affordable price, it's advisable to consult a certified installer. However, such a professional is typically booked months in advance, especially with the heating season around the corner. A busy homeowner like you doesn't have time for a long waiting list!

Thankfully, WhatCost can provide a shortcut. Complete our 30-second form, and within 48 hours, we'll connect you with up to 3 boiler professionals in your area. Compare their quotes and choose the one that fits your budget.

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Worcester Bosch is a long-time household name known for top-of-the-line quality, innovation, and versatility. Any boiler guide you look at will almost certainly mention this brand, and ours is no exception.

Worcester Bosch Greenstar 8000+ Style and Greenstar 4000 are regarded as their flagship models, offering the following features:

Viessman is another customer favourite, gaining recognition for its efficient, sustainable, and quiet boilers. Its ESyCool green cool energy solution received the IKU Award, showcasing its commitment to sustainability. 

Viessmann Vitodens 100-W and Vitodens 200-W solutions are the company's best-selling combination boilers, catering to both smaller and larger homes. Here's how they stand out:

Ideal Heating is an award-winning British boiler manufacturer recognised for its affordable yet high-quality boiler solutions, offering great value for money. 

Ideal Logic+ Combi² and Ideal Logic Max Combi² boilers are the brand's flagship models, sharing the following outstanding specs:

Vaillant has gained its reputation as a standard setter by introducing the first-ever high-efficiency boiler. Its boilers are recognised for their quiet operation, having been awarded the Quiet Mark accreditation by the UK Noise Abatement Society.

Vaillant's ecoTEC Plus and ecoTEC Exclusive with Green IQ are considered the company's best combination boilers. Apart from the 94% energy efficiency capabilities, their unique features include:

Baxi is another British boiler manufacturer known for its reliability and sustainability. Currently, Baxi owns other commercial heating brands, including Remeha, Potterton Commercial, Andrews Water Heaters, and Heatrae Sadia. Earlier in this guide, the latter was mentioned as the best electric combi boiler. 

Baxi 800 Combi 2, Baxi 600 Combi 2, and Baxi Platinum Compact Combi are recommended for homeowners on a budget. Their features include:

Deciding which is the best combi boiler on the market is never the same due to how heating preferences and water demands vary greatly from home to home. Therefore, as a homeowner, you should carefully consider your home's size, hot water usage patterns, energy efficiency goals, long-term running expenses, and your budget, of course. 

Top brands like Worcester Bosch, Viessmann, Ideal, Baxi, Intergas, and Vaillant all cater to different heating needs and offer excellent combi boilers with varying advantages. 

In this guide, we tried to provide you with all the information you need to make an informed decision. However, there might be other suitable combi boiler options that were not mentioned in our list. In any case, consulting a professional installer and comparing available quotes is absolutely necessary before investing in a boiler. 

An experienced boiler engineer can assess your home, recommend the best possible boiler option, and calculate the installation costs for you. This is the best way to protect you from unnecessary expenses and wasting hours on boiler comparison trying to find the best fit on your own.

With WhatCost, you can effortlessly get up to 3 quotes from reputable installers near you to kick-start your heating project in no time. Simply complete our short form below, and within 48 hours, we'll connect you with professionals from our vetted installer list.

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