Best Combi Boiler in the UK: 2021 Boiler Brands Review

With so many boiler models flooding the market, and all of them claiming to be the pinnacle of efficiency, reliability, and durability, it’s hard to pinpoint the actual best combi boiler.

So we ran numerous tests, dug deep into specs, warranty sheets, and reviews from people who own the products we feature. We sat down with local engineers to understand what makes a combi boiler good, and what customers must know to make an informed decision.

Heatable boiler clickable form

After months of research, we’ve compiled a list of the best combi boilers in 2021 and crafted a convenient guide with tonnes of useful information, like top boiler brands, boiler sizing, and boiler warranties. We’ll even show you how to compare boiler deals right here on your screen.

Read on to find out more!

Short on time? Jump to our recommendations for the best boilers for different homes:

Best small/medium combi boilers:

Best combi boilers for larger homes:

Best combi boiler with high heat output:

The Best Combi Boilers: How We Got These Rankings

We work with boiler installers, manufacturers, engineers, and consumers like you to arrive at a set of criteria for evaluating and ranking boiler models. These are the standards we’ve used to come up with our best combi boiler rankings in this article:

  • Warranty length
  • Reliability
  • Aftercare
  • Consumer reviews
  • Boiler design and specifications
  • Pricing

But while these factors helped us zero in on several top all-rounder models, every situation is unique and your property may be better served by a different Combi Boiler. That’s why we urge you to complete this anonymous survey from Heatable and explore the combi models recommended based on your answers.

What Are The Best Combi Boiler Brands?

Deciding which boiler brand is best is definitely up for debate — one installer’s opinion is going to differ from the next. However, here are the 5 reliable, reputable, combi boiler brands that are certainly worth mentioning.

1. Worcester Bosch Combi Boilers

Worcester Bosch offer some of the best boilers money can buy, and they’re by far the most popular in the UK. At my time spent working with a plumbing merchant, we’d sell at least 2 Worcester boilers for each 1 of all other brands combined.

They’re efficient, reliable, and come highly recommended by most boiler installers. More importantly, Worcester boilers have warranties of up to 10-years, which is huge!

The main let down used to be the price, which was typically on the higher end of the scale. However, Bosch are now working with large online boiler installation companies like Heatable, supplying Worcester combi boilers extremely cheap. Since online installers have relatively small overheads, these savings are passed on to you — the consumer.

You can easily get a fixed boiler price on your screen (without sharing personal details or getting annoying call backs) by filling out this online form.

2. Viessmann Combi Boilers

Renowned for their German precision, Viessmann are a producer that is synonymous with high-quality manufacturing. We also know that Viessmann’s combi boilers are highly efficient (A-rated) and thus budget-friendly in the cold months.

You may wonder — if they’re a premium brand, then why aren’t Viessmann boilers more expensive?

It’s all part of the company’s approach to the UK boiler market. Veissmann aims to promote its flagship models at highly attractive prices, make homeowners happy by fitting an excellent product in their homes, and slowly gain more slices of the UK boiler pie.

3. Ideal Combi Boilers

Ideal combi boilers are typically cheaper than Worcester’s, but this doesn’t mean that quality is compromised.

A model like the Ideal Logic Plus boiler with a 7-year warranty is comparable in price to the Worcester 25i or 30i, when fitted by an online boiler installation company like Heatable. And that’s simply because Heatable push the Worcester boilers at volume, and so are able to offer them at preferential rates, complete with an extra 3-years warranty.

4. Vaillant Combi Boilers

Some would argue that Vaillant is a big player in the UK boiler market.

But we’re not ranking best boilers based on the brand’s popularity. We think it’s important for homeowners to fit a product that follows the most rigorous design standards, packs premium components, is durable, and doesn’t break the bank.

And in truth, Vaillant won’t be that friendly to your finances — not at first, anyway. Proud holder of the 2017 Which? Best Buy award, Vaillant made sure the quality of its products is well reflected in the final sale price.

Vaillant’s ecoTEC plus boiler is the company’s flagship model. These combi boilers start at 25kW, which is an excellent choice for small-to-medium households that can afford the higher price point.

5. Baxi Combi Boilers

Baxi is the best boiler option on this list — if you’re on a tight budget. Although Baxi may not strike you as a premium boiler brand, their combi boilers are nothing short of durable.

The company has built a stellar reputation by offering award-winning customer support, efficiency, and lengthy warranties for its extensive lineup of innovative combi boilers.

The Baxi 600 and Duo-tec boiler ranges come with an extensive 7-year warranty, and the boilers in these series offer a rough equivalent of the Ideal Logic Plus. Meanwhile, Baxi’s Premium, Premium+, and EcoBlue Advance are similar to the Worcester Bosch combi boilers, and also have a 10-year warranty attached.

Our advice is to stay away from boilers with a warranty that’s shorter than 7 years, so it’s best to avoid the Baxi 100, 200 & 400 ranges.

Would you like to compare the best boiler prices back to back? Use this quick on-screen form.

What Is the Best Combi Boiler in 2021?

Now that you’re familiar with the top boiler brands, let’s dive into our list of the best available combi boiler models.

#1 – Worcester Greenstar I Combi Boilers

Let’s face it — when you think “boiler”, you think Worcester Bosch. 

At my time working at a local plumbing merchant, we were knocking out so many Worcester boilers, we’d get a full lorry load delivered every month, and “top-ups” daily. And that was just one branch.

Here’s why we think Worcester has some of the best combi boilers.

Efficiency

The most popular models in the range are the 25i and 30i combi boilers. But there’s also a range of system and regular I boilers too.

When they’re running on full power, Worcester’s combis will give you around 87.7% efficiency; this goes all the way up to 99.4% when operating at 30% of their maximum output.

Compared to what old boilers offer, this level of efficiency will save you BIG money on your gas bills.

Installation isn’t as expensive as you think

Worcester boilers are known as a premium brand, with a price tag to match. Well, that was until Bosch started supplying boilers to online installation companies like Heatable.

Regular Worcester installation from a local engineer is likely to be £200 more expensive than the equivalent from Ideal’s range. This number only rises (considerably) when you choose a national installer, like one of those running TV ads and such.

Now, compare these prices with Heatable’s. We’d typically expect a 25i to sit in the £1,900-£2,000 range. Yet here’s the quote we just got for a 25i (you can get yours within 90 seconds here).

Best Combi Boiler - Worcester Bosch Greenstar i from Heatable

The warranty is long

You can get up to 10 years warranty on the Greenstar I range. Very few manufacturers offer such a lengthy warranty period.

As we mention in most boiler reviews, the best combi boilers have a long warranty. That’s because the manufacturer’s warranty essentially reflects their confidence in the product. Simply put:

Short boiler warranty = “It’s probably going to break, and we don’t want to pay to fix it.”

Long boiler warranty = “This boiler has longevity, so we’re confident we won’t have to pay to fix it.”

Even if the manufacturer gets it wrong, there’s one person that doesn’t have to pay for those repairs — you.

It won’t self-destruct in winter

In the first year of this site being launched, we were averaging around 400-500 visits a day. Breaking into the second year, that started rising…then the temperature dropped below zero, for like 5 days straight. At the peak of the cold snap, the site got over 19,000 visitors in a single day.

My guestimate is most of the visitors were searching how to fix a frozen condensate pipe — a common boiler problem in winter.

That’s why Worcester have introduced preventative measures, such as the CondenseSure. This protects your boiler down to a stated -15°C.

So, unless you’re waving from the Arctic, you shouldn’t have issues with your condensate pipe freezing with a Greenstar I.

It won’t fit your kitchen cupboard

If you’re not planning to move your boiler, and it happily lives in an airing cupboard or is wall-hung, you’re all good with the Greenstar I. However, if you want to tuck your boiler away in a small space (such as a kitchen cupboard), this isn’t the boiler for you; it’s too big.

But while the Greenstar I may not be suitable, Worcester still has you covered. If you need a compact Worcester boiler, you can opt for the SI Compact instead.

Should you install the Greenstar I?

Yes, but which one? Each property is unique. Your home might have a longer heating run, more radiators, or even better insulation than the average. There’s not a one-size-fits-all solution.

The best thing to do? Grab a cuppa’, put aside around 90 seconds of your day and fill out this clickable multiple choice questionnaire from Heatable.

You won’t share any personal details (email, phone number, etc), and your efforts will be rewarded with a fixed price as well as your recommended boiler at the end!

#2 – Viessmann Vitodens Combi Boilers

We’ve said it before — Viessmann combi boilers are German design at its best.

Best Boilers - Viessmann Vitodens 050-W Combi BoilerTheir flagship models, the Vitodens range, include the Vitodens 050-W in two flavours (29kW and 35kw) and the more powerful Vitodens 100-W. Here’s why these models made our list.

Efficiency

We’re talking a class A rating for efficiency. And if you’re at least a bit concerned about the quality of our lives on Earth, know that the Vitodens range promise low CO2 emissions to help ease your carbon footprint.

This means you could save about £350 and 1,500kg of carbon dioxide a year.

Installation costs

A new Viessmann 050-W boiler from Heatable comes with a fixed price of £1,670. You can get your own quote online, and if you do before 3PM, you get next-day install, too.

We are we telling you all this because you probably expect premium prices to match the premium quality.

That’s not entirely the case with the 050-W. The price includes numerous freebies, such as:

  • free wireless heating controls
  • a free system cleanse
  • an Adey Sense filter

It’s a bargain if you compare it with other premium combi boilers.

Best Boilers 2021 Viessmann Vitodens 050-W from Heatable

Warranty: 10 years

Because Viessmann only uses high-quality components, it makes sense their boilers typically withstand the test of time.

That’s why the German manufacturer is able to offer an exclusive, 10-year warranty through Heatable for their fitted products.

Should I get a Viessmann Vitodens boiler?

The answer is a strong yes. But since each property is unique, we advise you to check out which model is the right one for you. Heatable has an online form that will take you only a couple of minutes to fill. You needn’t provide any personal information other than your postcode and the property type.

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

Baxi is a budget option, but their combis’ affordability doesn’t come at the expense of quality. There are 2 models we recommend, which, like all Baxi products, are built in the UK.

Best Cheap Combi Boiler - Baxi EcoBlue Advance combi boilerFor small to medium homes, the Duo-tec line promises up to 40kW, providing 16.4 litres/minute of hot water. That’s exceptional hot water performance if you ask me.

For larger homes, the more powerful EcoBlue Advance promises instant water while at the same time meeting the minimum energy efficiency rating required for Boiler Plus compliance.

Efficiency

Efficiency is a given for Baxi combi boilers — all models get a straight A for both running water and heating. So you can rest assured knowing that these boilers are good both for your pocket and the environment.

Installation costs

Fitted, a new Baxi Duo-tec 28 costs around £1,700, while the Duo-tec 28 commands an extra £150 – £200. That’s really affordable.

Warranty

If you use Baxi approved Gas safe engineers, the Duo-tec range gets a 7-years warranty, while the EcoBlue Advance comes with a whopping 10-years warranty.

Should I get a Baxi boiler?

If you’re looking for a quality budget combi boiler, then yes — Baxi is a stellar choice. Baxi combis have an appealing price tag, but these appliances are also incredibly well-made and offer superb warranty terms.

#4 – Ideal Vogue Combi Boilers

Ideal Boilers have been a player in the market for almost as long as we know the market :). Vogue range is their premium lineup of combi boilers, built with utmost care for perfection.

Good Boiler Makes - Ideal Vogue Gen2 Combi BoilerEfficiency

Straight A for both running water and heating. It’s also Energy Saving Trust-endorsed.

Installation costs

The Vogue 26 will set you back some £1,900, the Vogue 32 around £2,100, and the flagship Vogue C40 Gen2 will cost around £2,400. Fitted, of course.

Warranty: 10-years

The Vogue range comes with a 10-year parts and labour warranty. This, and the fact that Ideal Boilers are serious about providing high quality to homeowners, has gotten them the Good Housekeeping Reader Recommended status in 2013 and 2017.

One thing to keep in mind — you only get the 10-year warranty if the appliance is installed with an Ideal System filter.

Pros

  • Frost protection
  • Very quiet (award-winning design)
  • Backlit 3.5″ LCD full colour display.

Should I get an Ideal Vogue boiler?

The short answer is yes.

The long answer? We would personally go with a Worcester Bosch or a Viessman Vitodens for affording us more piece of mind, but getting the Ideal Vogue Gen2 combi boiler is not a bad deal at all.

Combi Boiler Sizing

Now that we’ve covered the best combi boiler models, it’s time to have a look at boiler sizing. Just keep in mind that these are estimates — if you want accurate boiler sizing, it’s always best to have an engineer assess your property. Alternatively, you can use Heatable’s calculator to get a recommendation based on your inputs.

Best combi boiler for 1-2 bed properties

Brand Model Warranty Price (installed)
Worcester Bosch Greenstar 25i 5-8 years from £1,770*
Worcester Bosch 28, 32 and 36CDI Compact 5-10 years from £2,050*
Viessmann Vitodens 050-W 29kW 10 years from £1,670*
Ideal Boilers Logic+ 24 7 years £1,750
Ideal Boilers Vogue 26 10 years when fitted with an Ideal system filter £1,900
Ideal Boilers I-Mini 24kw 2 years £1,650
Baxi Duo-tec 24 7 years £1,700

* prices available from HEATABLE

Best combi boiler for 3-4 bed properties

Brand Model Warranty Price (installed)
Worcester Bosch Greenstar 30i 5-10 years from £1,969*
Worcester Bosch Greenstar 34CDI 5-10 years from £2,100*
Viessmann Vitodens 050-W 35kW 10 years from £1,964*
Viessmann Vitodens 100-W 30kW 10 years from £2,119*
Ideal Boilers Logic+ 30 7 years £1,850
Ideal Boilers Vogue 32 10 years when fitted with an Ideal system filter £2,100
Baxi Duo-tec 28 7 years £1,850

* prices available from HEATABLE

Best combi boiler for 4-5 bed properties

Brand Model Warranty Price (installed)
Worcester Bosch Greenstar 42CDI 5-10 years from £2,750*
Viessmann Vitodens 100-W 30kW 10 years from £2,169*
Ideal Boilers Vogue C40 Gen2 10 years £2,400
Ideal Boilers Logic+ 35 7 years £2,200
Baxi EcoBlue Advance 10 years £2,100

* prices available from HEATABLE

Worcester boiler prices represent estimates for local installers, but tend to be much cheaper from Heatable given they’re one of UK’s largest installer.

See our boiler installation guide if you are having your boiler replaced.

Check the Combi Boiler Warranty

One of the key things you need to focus on when choosing the best combi boiler is the warranty. To avoid getting stuck paying for repairs and replacement, you must always strive to get the longest warranty possible.

Which isn’t always as easy as it seems — some of the more affordable brands and models come with ridiculously short warranties; others require a specific installer. This is another reason we like to recommend getting a boiler quote from Heatable. The online installer gets preferential rates from top boiler brands like Worcester Bosch, and offers a 10-year warranty on their appliances.

Combi Boilers Warranty Guide

Warranties are confusing, even when you get them from the best boiler manufacturers.

Some manufacturers charge for additional warranty periods, others give you access to longer durations if you use their accredited installer networks. Top boiler manufacturers regularly run promotions, including extended warranties, so the coverage terms do change from time to time.

That’s why it’s always wise to double check warranties before purchasingThe warranty period may just be the factor that helps you decide on the best combi boiler for your home.

The Combi Boiler Fine Print to Look Out For

Warranty terms and conditions are usually long-winded and full of legalese. However, the points below are the most essential factors you’ll want to consider to meet your end of boiler warranty conditions:

  • Register your warranty within 30 days
  • Installation has to be by a Gas Safe engineer
  • Some brands may require you to use an installer from their network to gain access to additional warranty
  • Annual servicing from a Gas Safe engineer

And here are the things that typically void a warranty:

  • Scale build up (typical in hard water areas; you can combat this issue by installing a lime scale inhibitor)
  • Sludge build up in a system (you can control this issue by installing a magnetic system filter and getting your heating system cleaned with every service)

Worcester Bosch: Warranty Explained

Most Worcester installers hype the 10-year warranty on offer, but not all Worcester boilers come with a 10-year warranty as standard. Often, you’ll have to do some research to find ways to extend standard warranties.

For instance, if you’re using an accredited installer, you’ll get up to 10 years on the CDI range. A Gas Safe engineer in the Worcester Bosch accredited installer network will also allow you to get a higher duration on other ranges.

Then there are companies like Heatable that offer 10-years on all products, but that’s because they have a special relationship with Worcester.

Here’s a quick table outlining warranty durations on various Worcester boiler ranges.

Installation details CDI Range I Range SI Range
Worcester boiler only 5 years 5 years 5 years
With accredited installer 7 years 7 years 7 years
Worcester boiler, and branded magnetic system filter 6 years 6 years 6 years
With accredited installer 8 years 8 years 8 years
Worcester boiler, filter branded controls 7 years 6 years 7 years
With accredited installer 10 years 8 years 9 years

Straight up, Worcester-branded parts are not cheap. To get their extended warranty, you have to buy them!

The Worcester system filter will cost more than £130. An equivalent from Adey (they specialise in filters and chemicals) will cost around £100.00.

The Worcester Wave timer will cost around £225. Whereas the Nest (company owned by Google) Smart Thermostat will cost less than £200.

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


Ideal Boilers: Warranty Explained

Ideal’s warranty is, well, ideal. It’s just so simple.

They have their own an installer network, but they also recognise that installer standards are set by Gas Safe, not their network. This means that you can use any Gas Safe-registered installer to get Ideal’s warranty.

Here’s what Ideal’s warranty terms look like:

Product Warranty
Ideal Instinct 2 years
Ideal Logic 2 years
Ideal Logic Plus 7 years
Ideal Vogue 10 years

Have a quick look here to make sure you don’t break Ideal’s T&Cs


Baxi Boilers: Warranty Explained

Product Warranty
Duo-tec 7 years
Platinum Combi 10 years

Baxi do have an installer network, but any Gas Safe registered engineer can be the installer. You can read the full T&Cs of Baxi’s warranty here.


What is your next step now that you’ve read our best combi boiler guide?

Hopefully, our guide to the best combi boilers gives you all the information you need to decide which brand and model to buy.

Still confused by which is the best combi boiler brandSkip over to our boiler installation cost guide.

Or, drop us a line through our contact form or in the comments below, and we’ll do our best to help you out.

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  1. The Worcester Bosch Greenstar range is by far the most popular choice with any boiler installer I’ve spoken to recently. The warranty shows the brands confidence in the build quality and parts used in the boilers. They are just unfortunately not affordable for all unless finance options are an option.

  2. Local Authority Eco Scheme Energy Company Obligations (ECO) offering replacement Potterton boiler with 2-year Warranty. Our present boiler is a Worcester Greenstar 37CDi Combi which is 12 years old but has a new Heat Exchanger installed last year and we have a British Gas Maintenance contract. We want to know if we should stick or twist as suggestion is that the present boiler might only last another 3 years. Advice would be helpful.Thanks.JMCD

    1. Hi James, Worcester’s are usually great units. Personally, I don’t trust a boiler with a warranty lower than 5 years. I’m not sure if this answers your question or not. I would go for boiler cover, I guess, and if it breaks the cover will … cover it 🙂

  3. Quite interesting range of boilers but would be inclined to opt for highly rated Worcester or Viessmann Combi to replace my conventional boiler in a 2 bedroom flat.

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