Cosy home - Best combi boiler

5 Best Combi Boilers

So what is the best Combi Boiler in 2024? Keeping your home warm is no joke. If you choose the wrong boiler, it could lead to extra expenses fixing or even replacing it entirely. You want a heating system you can rely on – one that will last you a long time with minimal headache. This is where combi boilers come in. 

Smart meter - Best combi boiler
Smart meter – Best combi boiler

They take away a lot of hassle and ensure your home is cosy throughout the year. What is the best combi boiler out there right now? Fortunately, there are at least five highly dependable units to check out. The hard part is deciding which is the best fit for your home and budget. 


What is a combi boiler? 

As opposed to regular boilers that have separate components, a combi – or combination – unit contains both a water heater and central heating boiler. A basic boiler explanation is that you turn on the tap and the system draws water straight from the mains – no cylinders required. This often means that the pressure is much better than with regular systems. 

Combi boilers are very popular today because they’re smart and save up a lot of space. Basically, instead of having one or two ugly tanks sitting around the house, you get everything you need to heat and send water around the house in a single device. It’s connected to the main and features many handy controls to make the whole system much more manageable.  

In fact, the better the model the more you’ll be able to plan and calculate your expenditure over time. A combi boiler’s design makes this possible by including features like a smart meter, thermostat, timer or all these together. More than anything else, combination boilers are valued for bringing more convenience and control to homeowners. 

Their growing popularity are making cylinder systems a thing of the past for UK households. And providers are competing to provide the best deal possible. In other words, there’s no better time to consider investing in the best combi boiler on the market. 

Pros and cons of a combi boiler 

Take a look at exactly what you’d be gaining from a combination boiler – especially over other heating systems. Why not make a list of advantages to your home, as well as things you’d need before installing a combi boiler? For example, think about whether you have a good place for it, what alterations are necessary and how much it would all cost.  

Combi boiler advantages

  • Perfect for small properties 
  • Compact system 
  • No need for a cylinder, tank or as much pipework 
  • Takes up little room and gives you more living space, especially in the loft 
  • Faster water distribution and higher pressure due to sourcing water from the mains 
  • Reduced sludge build-up 
  • Safer drinking water because it comes straight from the mains and not a tank 
  • Cheaper and easier to install than other units due to its size and simpler system 
  • Easier to repair and find replacement parts 
  • Smart features can result in reduced heating bills 

Combi boiler disadvantages: 

  • Hot water is limited to one shower or tap at a time 
  • Breakdowns result in loss of hot water and heating 
  • Power showers can’t be used alongside a combi boiler 
  • Not great for large properties that may need to run multiple outlets simultaneously 
  • Installation and performance depend on the mains’ condition and pressure 
  • Old piping and radiators may need replacing to be able to handle the increased water pressure 

What is the best combi boiler? 

Boiler advantages - Best combi boiler
Boiler advantages – Best combi boiler

This decision comes down to a few factors, such as the size and structure of your home – not to mention the cost. Take a look at the following four leading models and think about what might work best for your needs. 

Worcester Bosch Greenstar i Boiler

Worcester is generally considered one of the top brands in the combi boiler market with this particular model outshining all its cousins. It’s ideal for small to medium houses – meaning no more than 1-3 bedrooms. Here are a few more specifications you may find useful. 

Average Price (installation excluded):  £850 – £950 
Efficiency:  94% 
Dimensions:  71 x 40 x 33cm 
Models:  25kW and 30kW 
Water flow rate:  10.2 – 12.3 litres / minute 

If your home veers towards the larger end, go for the 30kW model. Keep exploring what makes this boiler special and you may have the perfect solution. 

Key features 

  • Comes with pre-plumbing and required piping 
  • Contains a Condensesure Siphon, which prevents condensate pipes from freezing – requires 32mm pipework of no longer than 3 metres 
  • Interior expansion tank 
  • Easily removable fan and panel 
  • Light in weight  
  • Quiet boiler 
  • Clearly displayed information 
  • Mechanical, digital or advanced controls available for adjusting flow and temperature 
  • High heating efficiency when combined with Bosch EasyControl smart system 
  • Low energy pump 
  • LPG and solar compatible 

Viessman Vitodens 050-W Boiler

Among the best combi boiler brands you’ll come across, Viessman is a giant. While there are several good models to consider, this one has earned a lot of praise for its value for money. A modern house of medium size would benefit the most from this model’s abilities and cool look. 

Average Price (installation included):  £1,050 – £1,149 
Efficiency:  97% 
Dimensions:  70.7 x 40 x 35cm 
Models:  29kW and 35kW 
Water flow rate:  11.8 litres / minute 

Many more perks await if you invest in a trusty Viessman system. Why not add some underfloor heating while you’re at it?  

Key features 

  • Suitable for up to 3-bedroom homes 
  • Extra compact 
  • Quiet boiler 
  • Digital LCD interface 
  • Wireless thermostat available 
  • Smart tado° system 
  • Weather compensation available 
  • Class A rated energy efficiency 
  • Low CO2 emission 

Vaillant ecoTEC Plus Boiler

Once again, when looking for the best combi boiler deals, this is a name many homeowners have come to trust – and for good reason. Vaillant’s high standards ensure efficiency and convenience for their customers. This unit is suitable for any home size without missing the mark on well-rounded heating and water distribution, as well as precise management of the overall system. 

Average Price (installation excluded):  £900 – £2,100 
Efficiency:  89.3% 
Dimensions:  72 x 44 x 33.8cm 
Models:  25, 32, 35 and 38kW 
Water flow rate:  10.5 – 15.9 litres / minute 

As you can tell, this is a brand that can satisfy all home sizes. Compare its features with the other models’ and it may the best combi boiler for you.  

Key features 

  • Especially good for large properties 
  • 5-second water delivery 
  • Low energy consumption and high efficiency due to modulation range of up to 1:6 
  • Flame life detection system 
  • Quiet boiler 
  • Two-stage protection from freezing 
  • LPG compatibility 
  • AroTHERM air to water heat pump hybrid system compatibility 
  • Mechanical, digital and vSmart controls 

Ideal Logic+ Boiler

The next suggestion for the best combi boiler in the UK is this special range. It won the Queen’s Award for Enterprise in 2013, Good Housekeeping status in 2013 and 2017, and a Quiet Mark accreditation. Logic+ boilers are definitely worth the investment, but make sure you get the right model. There’s one less option compared to the Vaillant range, but each one is just as efficient. 

Average Price (installation excluded):  £725 – £925 
Efficiency:  94% 
Dimensions:  70 x 39.5 x 27.8cm 
Models:  24, 30 and 35kW 
Water flow rate:  9.9 – 14.5 litres / minute 

The number of options available makes this another good brand to check before any others. Their star series of combi boilers shows how well they know the needs of UK homeowners in 2020. 

Key features 

  • Good for properties of different sizes 
  • Compact design 
  • Digital display 
  • Light weight 
  • Pre-wired and PRV rear pipe included 
  • Frost protection 
  • Weather compensation available 
  • Condensate connection 
  • Additional flues available 
  • LPG compatibility – but only with the 30kW unit 

Baxi Duotec Combi 28 Gas Boiler 

Finally, we have Baxi’s super energy efficient and versatile series. It’s slightly larger than the other suggested brands, but its performance makes up for it. There are different models and so a nice variety of options for homes of different sizes and needs.  

Average Price (installation excluded):  £775 – £1,025 
Efficiency:  88.6% 
Dimensions:  78 x 45 x 34.5cm 
Models:  24, 28, 33 and 40kW 
Water flow rate:  11.5 litres / minute 

There’s much to appreciate about this low-cost and efficient combi boiler. If you’re looking for an affordable and reliable system, don’t overlook this option. You could even browse the brand’s other ranges. 

Key features 

  • Suitable for up to 4-bedroom homes 
  • Includes all wiring and piping necessary for mounting 
  • Variety of flues to choose from 
  • LPG compatibility for the 28kW model 
  • Mechanical, digital or uSense smart controls 

Finding the best combi boiler for your home 

Cosy home - Best combi boiler
Cosy home – Best combi boiler

Several factors make up the ideal boiler for any given property. It’s not just a matter of low price. Firstly, you need to find the right place to put the boiler and measure the space’s dimensions. Then you’ll be able to choose the best combi boiler to fit that cupboard or section of wall. 

Checking your mains is another vital step. If the water pressure is too low, for example, a combi boiler won’t be suitable for your property. There’s an easy way to test the system.

DIY mains pressure test

  1. Pour tap water on full pressure into a 1-2 litre jug for 6 seconds 
  2. Multiply the volume filled by 10 
  3. If the total is less than 10 litres per minute, your mains water pressure is low – the ideal flow rate is 15 or more 

Before making a purchase or installing the new boiler, make sure the mains are up to par. If the problem can’t be fixed, explore other boiler options. They can be just as efficient as combi boilers despite the extra cost. 

Another issue to consider is the pipework. If you’re switching from an older cylinder-based system, the original pipes may not be able to cope with the higher water pressure. Your budget may need to take such changes into consideration too. 

Finally, you need to calculate how much heat output your house needs. The property’s size and number of radiators are key factors as they affect how far hot water will have to travel. A unit of up to 27kW is enough for less than 10 radiators. If you have 15, a 28-34kW system would be best. Any more than that and you’ll need to look for an output of at least 34kW.  

All these details can have an unavoidable impact on the overall cost of installing a combi boiler. So, it’s a good idea to prepare by saving up and making any required improvements ahead of time. Pace your progress and spending for minimum amount of stress and unpleasant surprises. 

Combi boiler installation costs 

Unless it’s part of your home insurance cover, installing the boiler won’t always be included in providers’ services. Researching this average cost is another way to prepare for the often-complicated process of getting a new combi boiler. Keep in mind that upgrading from a cylinder-based to a combination system is generally more expensive than simple replacing an old combi unit with a new one.  

Combi boiler installation service  Average cost 
Replacement  £500 – £700 
Upgrade from regular system  £1,500 – £3,500 
System flush  £200 – £400 

Extra combi boiler expenses 

Boiler budget - Best combi boiler
Setting a budget – Best combi boiler

It’s a good idea to prepare for extra costs to the new boiler before it’s installed. This includes things that will impact your overall budget. Installing the boiler alone can be a major expense that isn’t always mentioned in each brand’s price ranges. Take a close look at the numbers and if something isn’t clear, don’t hesitate to ask the manufacturer or installer exactly what their quote covers.  

It’s also advised to get a system flush before changing boilers, which means an engineer will need to get involved. Doing a chemical or power flush is best left for someone with experience – in fact, you should leave anything to do with your heating system to a Gas Safe-registered engineer. Whether the boiler’s provider offers this service or you hire an independent professional, it counts as another important expense you should save up for.  

Checking and upgrading different parts of the house’s heating and water systems may also be needed – pipes, radiators, water pumps. This way the brand new combi boiler won’t find obstructions and other problems once up and running. Basically, the house must be able to cope with everything the boiler adds to the system. So, the more you invest in this preparation, the fewer bad and expensive surprises you’ll have to deal with. 

The best combi boiler offers peace of mind, as well as a well-designed heating system. Once you’ve settled on a brand and model, create a checklist of anything else you’ll need to do and pay for to ensure the installation goes smoothly. 

Best combi boiler installers 

Once the new boiler is up and running, you need to make sure it meets safety regulations. To do this, a Gas Safe registered engineer must pay you a visit. They’re trained and qualified to carry out this very task before leaving you with a certificate detailing all the passed safety checks. 

Unfortunately, illegal gas safe engineers are a risk you should look out for. Reliable heating engineer like those you’d work with after filling in the form below will be on the Gas Safe Register. What you should do before hiring an engineer is check their Gas Safe ID card. If their photo, dates, licence number and company are legitimate, you can feel safe booking them for an inspection. 

Have you used any of these boilers before? Tell us all about your experience, good or bad, @Quotatis

Electra Nanou

Electra Nanou is a Content Marketing Intern at Quotatis. She writes a range of digital content related to products and services, while striving to make every online experience as pleasant and helpful as possible.

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