Best Combi Boiler in 2023: Which One Should I Buy?

If you are looking to buy a new combi boiler, this is the guide for you. Our experts have researched the market and in this guide, we will reveal the best boiler manufacturers, the top combi boiler models, and our top tips on how to save money when getting a new boiler bought and installed.

Identifying and ranking the best combi boilers currently on the market in the UK is no easy feat. There are multiple manufacturers with dozens of different models and our experts have spent weeks laboriously road-testing and rating each one.

But the results are now in, we have compiled them, and are now proud to be able to announce the exclusive CompariHome recommendations for the best combi boilers in the UK.

In this guide, we will outline the best manufacturers, the best models, and the best way to save big sums when you buy and install a new combi boiler. It is one of our most comprehensive guides ever and promises to answer all your combi boiler questions.

A brief overview:

What are the best small/medium combi boilers?

  1. Worcester Greenstar 25i
  2. Viessmann Vitodens 050-W 29kW
  3. Baxi Duo-tec 24 – 24kW / 30kW

What are the best large combi boilers?

  1. Worcester Greenstar 34 CDI
  2. Viessmann Vitodens 100-W 35kW
  3. Ideal Boilers Vogue 40

What highly powerful model is the best combi boiler?

  1. Worcester Greenstar 42CDI
  2. Viessmann Vitodens 111-W 35kW
  3. Ideal Boilers Vogue C40 Gen2


The best combi boilers: How we tested

Before we reveal our top recommended combi boilers, it is important to give you some insight into our methodology so you know how we have reached our conclusions.

Our experts were as one in the view that the most important factor to look for in a new combi boiler is the warranty. Does your new combi boiler come with a warranty and how long does it last for?

You’ll see from our warranty guide, we rate leading boiler brands such as Baxi, Ideal Boilers and Worcester Bosch highly in this area.

Price is likely to be your main consideration when buying a new boiler too. But that doesn’t mean you have to opt for a budget brand. A lot of top brands including Worcester Bosch have started working with online boiler installation platforms like Heatable.

Because these online installation company can buy in bulk and have low overheads, they are able to pass on huge savings to their customers making a high-end boiler suddenly become more affordable.

To see what I mean, you can jump online and get a fixed price in around 2 minutes.

What is the best combi boiler brand?

When buying a new boiler, your focus should be on the combi boiler warranty. Ideally, you should be looking for a minimum of a 5-year warranty on any new combi boiler, but there are plenty of boilers on offer with 7-years upwards. And as we will see, it is possible to get a mammoth 10-year warranty on some boilers too.

Choosing the best combi boiler is up for debate, and one gas engineers opinion is going to vary from the next. However, here are the main combi boiler brands that all of the engineers we work with spoke well about:

1. Worcester Bosch Combi Boilers

Worcester Bosch is one of the top combi boiler manufacturers on the market and one of the most popular too. Most heating engineers will tell you that they expect to sell at least two Worcester Bosch boilers for every one of the other brands they offer.

The reason for this is simple. They are efficient, reliable and highly recommended by engineers and customers alike. Crucially, they’re available with a warranty of up to 10-years, which is huge!

The big downside to Worcester Bosch used to be their high prices but in recent times even this has changed. And with so many boilers on finance deals, everyone can “afford” one.

Worcester Bosch is now working with the biggest online boiler installation companies including Heatable. This means you can now get a Worcester Bosch combi boilers extremely cheaply.

If you want to see just how affordable they are, head over to the Heatable website for a fixed-price no-obligation quote.

2. Viessmann Combi Boilers

Viessmann boilers are German manufactured and tick all the stereotypes as they are both reliable andmanufactured to an extremely high quality. Viessmann’s combi boilers are also renowned for being highly efficient (A-rated), making them extremely friendly to both the environment and your bank balance.

But why are Viessmann boilers so affordable if they’re a premium brand?

The company’s strategy for the UK market is to promote its flagship models at highly attractive prices to build a larger market share. This is great news for you as it means you can get a terrific boiler at a great price.

3. Ideal Combi Boilers

Ideal combi boilers tend to be cheaper than Worcester Bosch models, but that doesn’t necessarily mean they are of a lower quality.

A model like the Ideal Logic Plus comes with a whopping 7-year warranty but is comparable in price to the Worcester Bosch 25i or 30i, if you get it installed by online boiler installation companies. That’s because the likes of Heatable can offer Worcester Bosch at preferential rates, complete with 3-years warranty more warranty.

4. Vaillant Combi Boilers

Vaillant combi boilers all come with rigorous build standards, premium components, impressive durability, and competitive running prices.

Proud holder of a Which? Best Buy award in 2017, Vaillant ensures that the quality of its products is reflected in the final sale price. But this can mean they are more expensive than the likes of a Worcester Bosch.

The ecoTEC plus is the company’s flagship model. It starts from 25kW making it an excellent choice for a small to medium household who can afford to pay a little more for it.

5. Baxi Combi Boilers

Baxi is the budget option on this list. While they are a low-cost manufacturer, their boilers are still durable and have a great reputation for customer support and amazing warranties as well as offering customers an extensive lineup of innovative combi boilers.

The Baxi 600 and Duo-tec range come with an extended 7-year warranty, while you can also get the Premium, Premium+ and EcoBlue Advance models with a 10-year warranty attached, the same as a Worcester Bosch.

Because we would usually advise users to stay away from boilers with less than a 7-year warranty, we suggest avoiding the cheapest models such as the Baxi 100, 200 & 400 ranges.

What is the best combi boiler?

Our researchers have found these to be the best combi boilers on the UK market:

#1 – Worcester Greenstar I Combi Boilers

The most popular models in the Worcester Bosch range are the 25i and 30i combi boilers.

When running almost flat out, they’ll be giving you around 87.7% efficiency. You can get this as high as 99.4%if you run it at around 30% of its maximum output.

Compared to older models from almost any manufacturer, this is going to be saving you BIG money on your gas bills.

Installation doesn’t have to cost the earth

While Worcester Bosch has a reputation for being a high-end boiler brand, its decision to work with online installation firms like Heatable have suddenly made the price of a Worcester Bosch boiler much more affordable.

Getting a new Worcester Bosch boiler installed by a local engineer is likely to set you back around £200 more than the equivalent from Ideal’s range. If you go with a national installer like British Gas, you can expect to pay even more. But with Heatable, a Worcester Bosch can end up being cheaper than other more budget models.

For example, we would expect a Worcester Bosch 25i combi boiler to cost around £1,900-£2,000. But on Heatable, it is listed at just £1,770. TO see for yourself, just fill in their online form for a no-obligation, fixed-price quote.

A huge warranty

The length of the warranty offered with a boiler is a good indicator of how long that boiler is likely to last. A short warranty means it’s probably going to break, and the manufacturers don’t want to have to pay to fix it. A long warranty means it is likely to last and we are confident we won’t have to pay.

You can get up to 10 years warranty on the Worcester Bosch Greenstar I range which tells you all you need to know about how long it should last.

Even if they’re wrong and it does go wrong, the good news is the one person who doesn’t have to pay for it to be fixed is you.

It will survive the winter

Boilers always tend to go wrong in winter when they are being used more and are needed most. That’s why Worcester Bosch have introduced special preventative measures, such as the CondenseSure. This is designed to protect your boiler down to a stated -15 and should ensure it makes through even the coldest of winters.

The one downside

If there is one downside to the Worcester Bosch Greenstar I range it is the size. If you want to tuck your new boiler away somewhere discrete, this isn’t the one for you. It is much too big for that.

But if you want to combine all the quality of a Worcester Bosch boiler with a compact size, there is a better option for you; take a look at their SI Compact range instead.

RELATED READING: Worcester Greenstar RI Boilers Reviewed

Should you choose the Greenstar I?

Yes, the Worcester Bosch Greenstar I is a terrific boiler and we highly recommend it. But whether it is the right boiler for your property will depend on a whole host of factors.

The best way to find out in our view is to head over to the Heatable website and fill in their multiple-choice questionnaire. It will take about 90 seconds and will let you tell them all about the type of property you live in and recommend the best boiler at the best price for you.

You won’t need to enter any personal details (postcode, phone number etc), and you’ll have a fixed price quoteas well as a recommendation of a great boiler at the end too.

#2 – Viessmann Vitodens Combi Boilers

Viessmann boilers are German design at its best. Their flagship models, the Vitodens range, include the Vitodens 050-W (available in 29kW and 35kw) and the more powerful VItodens 100-W. But what is it about Viessmann boilers that make them stand out from the rest?


As you would expect from a German manufactured boiler, all Viessmann boilers get an A* for efficiency. The Vitodens range also promises low CO2 emissions to help keep your carbon footprint down and raise your green credentials too.

Our experts estimate that a Viessmann Vitoden’s boiler could save each household about £350 and 1,500kg of carbon monoxide a year.

Installation costs

If you buy a new Viessmann 050-W from Heatable, you can expect to pay a fixed price of £1,670. If you place your order before 3pm, you could even get it installed the following day too. So, while you might expect a Viessmann boiler to be expensive, they are in fact extremely competitively priced if you buy through Heatable.

That price also includes free wireless heating controls, a free system cleanse and an Adey Sense filter. It’s areal bargain when you compare it with other premium combi-boilers.

Warranty: 10-years

Viessmann only uses high-quality components in their boilers which is why you can rely on them to stand the test of time.

They are obviously confident in this too and that’s why they are able to offer an exclusive 10-years warrantythrough Heatable for their fitted products. It’s the biggest warranty you’ll get for a combi boiler.

Should I get a Viessmann Vitodens boiler?

Again, we are very happy to recommend the Viessmann Vitodens range of boilers.

But again, you should head over to the Heatable website and go through their survey to check it is the right boiler for your property.

#3 – Baxi Duo-tec & EcoBlue Advance Combi Boilers

We know price is a big factor for a lot of people and Baxi is a budget option. But that’s not because they have sacrificed quality for affordable pricing. Baxi boilers are still dependable.

If you live in a small to medium home, the Baxi Duo-tec offers up to 40kW providing 16.4 litres/minute hot water. That’s exceptional hot water performance!

If you live in a larger home, the more powerful EcoBlue Advance can also guarantee instant water while alsomeeting the minimum energy efficiency rating required for Boiler Plus compliance.


All Baxi boilers get a straight-A for both running water and heating. They are as energy efficient as a combi boiler can be meaning you can be confident you a minimizing your carbon footprint too.

Installation costs

A new Baxi Duo-tec 28 will cost you around £1,700 while the Duo-tec 28 is another £150 – £200 on top of that.

That’s a really competitive price but it is worth thinking about how it compares to the Worcester Bosch or Viessmann models too.


If you get your Baxi boiler installed by approved Gas safe engineers, the warranties are pretty impressive. The Duo-tec range comes with a 7-years warranty while the EcoBlue Advance has a massive 10-years warranty.

Should I get a Baxi boiler?

Baxi boilers are a quality product at an affordable price and come with excellent warranty terms too. We are happy to recommend both the Duo-tec or the EcoBlue Advance combi boiler ranges.

#4 – Ideal Vogue Combi Boilers

Ideal is a high-quality British boiler manufacturer. Their Vogue range is their top-end set of models and are well-built and high-performing.


Top marks for both running water and heating. The Ideal Vogue range is also endorsed by the Energy Saving Trust.

Installation costs

An Ideal Vogue 26 will cost you around £1,900. If you choose the Vogue 32 you can expect to pay £2,100 while at the top end of the range, the Vogue C40 Gen2 will set you back around £2,400.

Warranty: 10-years

The Vogue range comes with a 10-year parts and labour warranty as standard. This is a testament to its longevity and explains why Ideal Boilers got a Good Housekeeping Reader Recommended status in 2013 and 2017.

It is worth noting though that you only get a 10-years warranty if your Ideal boiler is installed with an Ideal System filter.

Should I get an Ideal Vogue boiler?

There is a lot of good things to say about the Ideal Vogue range. Our view is that Worcester Bosch and Viessmann boilers still offer better value for money and deliver more peace of mind, but certainly, the Ideal Vogue Gen2 combi boiler is a pretty good deal.

A short guide to Combi boiler warranties

Boiler warranties can be confusing and since we have said they are a key factor in choosing your boiler, it’s only right that we explain a little more about them to help you understand them.

First, you need to check the rules. Some boilers will require you to use accredited installer networks if you want to benefit from the extra warranty that is available. Some manufacturers may then charge for that additional warranty too.

Top boiler manufacturers regularly run special promotions (including extended warranties), so they can change from time to time too.

This is why it is vital to double-check warranties before you buy your boiler.

Read the fine print

A warranty will usually come with reams of fine print and it can be tempting to skip over these.

Don’t though, because these are the most important things you’ll need to consider and can include rules like:

  • Register your warranty within 30 days
  • Installation must be by a Gas Safe engineer
  • A requirement to use an installer from their network to access additional warranty
  • The requirement to have an annual service from a Gas Safe engineer

The fine print will also detail what voids the warranty and this is worth checking out in advance too. It could include things like:

  • Scale build-up (common in hard water areas but can be dealt with by installing a lime-scale inhibitor)
  • Sludge build up in a system (this can also be dealt with by installing a magnetic system filter and having it cleaned with every service)

Worcester Bosch: Warranty Explained

Most Worcester Bosch installers will make a fuss about the 10-year warranty on offer, but it is important to note that not all Worcester boilers come with a 10-year warranty as standard.

There are companies like Heatable that do offer a 10-year warranty on all Worcester Bosch boilers, and you will also get up to 10-years warranty on the CDI range if you use an accredited installer.

Using a Gas Safe engineer in the Worcester Bosch accredited installer network will also allow you to get a slightly longer warranty on some other ranges too.

You will also have to use Worcester Bosch branded parts to get their extended warranty and these are often not cheap either. For example, a Worcester Bosch system filter will cost more than £130. Equivalents are available for around £100 but if you want to keep that warranty you will have to pay more.

The finer details of the Worcester Bosch boiler warranty can be found here.

Other warranties explained

Ideal’s warranty is far more straightforward. They do have an installer network, but they also recognise that Gas Safe sets the standard for installers, so you can use any Gas Safe registered installer to get their full warranty.

Baxi does have an installer network, but again they will allow any Gas Safe registered engineer to install their boilers.

RELATED READING: Understanding costs for new boilers

What’s the next step?

Choosing the best combi boiler can be a stressful decision so we have attempted to pack as much useful information into this guide as we possibly can.

We have explained how warranties are a terrific litmus test for how reliable your new boiler can be and given you some tips to follow as well as some advice on how warranties work and how to read the fine print.

We have outlined the top manufacturers and recommended the best combi boiler models on the market in the UK right now. We have also explained how you can use an online installation company like Heatable to save big money on some of the best brands around.

If you have any questions or comments about anything in this guide, or a great bit of advice for our readers that we haven’t mentioned in this guide, why not share it with us all today by using the comment box below?

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