The Best Combi Boiler of 2025: The Good, Bad & Ugly

Qualification; 50K fitted

Natural gas, or ‘natures candy’ allows us to heat our homes through the magic of combi boilers, rapidly providing us with both heating and hot water.

But some boilers are worryingly skilled with foundation and blusher.

They look nice on the outside, but they’re just Fiat Panda’s with private reg plates. The lights came on in the club and you realise you’ve agreed to take home a lippy potato.

We’ve fitted around 50,000 combi boilers in the UK (including some bad ones).

But, for you – you positivity hippo - here are the best combi boilers: 

[1] Worcester Bosch 👑

The stock answer, and with good reason. Worcester-Bosch dominate the UK boiler market with remarkable volume backed up with genuine class. Like an Italian opera singer with silk pants.

Worcester makes the best combi boiler for two reasons. The only two reasons that matter, in fact.

Their build quality is insanely robust.

Plus, their post-installation service (in the unlikely event you need it) is absolutely remarkable.

We’ve seen the worst of the boiler world over many winters and most combi boiler brands will send out repair engineers at the speed of a bleeding beached whale, desperately attempting to will itself back into the water.

Worcester’s best combi boiler? The 4000, of course.

It’s relatively compact dimensions, great hot water delivery and solid efficiency makes it the go-to for most UK homes.

Couple that with Worcester Bosch’s aftercare, and you’re quite literally on to a winner.

Want to read more? Read our Worcester Bosch 4000 review.

[2] Vaillant

A slave to lists, it’s only numerical conformity that places Vaillant in second place. Their combi boiler quality isn’t bettered in market and it’s perhaps only a lack of exposure that has them sitting behind Worcester’s best combi boilers.

A shame really, as it seems you can’t win whether you’re exposing yourself or not these days.

Here’s a quick list of the combi boiler range (because, we all love a list).

So, what’s the best Vaillant combi boiler? The ecoTEC Plus.

Sitting slightly higher in the price range, the ecoTEC Plus carries a well-deserved premium label.

But, it’s power, efficiency and performance justify it - with ease.

It’s re-assuringly expensive.

Want to know why? Read our in-depth review of the ecoTEC Plus.

[3] Viessmann

The boiler that crept up on the UK when it wasn’t looking.

Not content with just shouting “Boo!” – they slithered their way into cupboards of enormous amounts UK homeowners. In fact, the Viessmann 050 is our best ever selling boilers.

They blend typically efficient German engineers with a very competitive price point. The leading manufacturers were not thrilled to see them enter the market.

Best Viessmann Combi Boiler? The Vitodens 100.

A bit like the Worcester Bosch 4000, the 100-W is the sweet and tasty spot in the range.

It’s not the cheapest, but it’s not the dearest.

It’s not the least powerful, but it’s not the most either.

It’s a fantastic, really well built combi boiler that’ll suit most UK homes down to a tee.

Want one? Buy one.

Want to know more? Read our review.

[4] ATAG

Often offering hilariously long warranties that will see out your grandchildren, ATAG are a much more niche choice that are a little harder to come by. They’ll usually be fitted exclusively by independent engineers hooked on the heroine of their point system. Fortunately for you, they’re also ruddy good combi boilers that ironically leave you unlikely to need that mega warranty.

Brand pick (Best ATAG combi):
ATAG iC combi boiler (ahhh, I seeee)

ATAG’s proud description of their combi boilers:

It’s comforting to think of a world in which dwellings of families (size; large) are hunkered down somewhere throwing celebratory parties over the efficiency of a Dutch boiler. Maybe everything is going to be OK.

Bad combi boilers

Navien ← Read a screaming review.

Being handed out like fizzy drinks at Diddies house, Navien are pretty new to the UK boiler scene and represent a little bit of a gamble.

Ferroli

Free with every copy of The Big Issue, Ferroli’s strike fear into the hearts of all good combi boiler engineers. You can rest easy though because the only time you’re likely to utter the words Ferroli is when you’re telling an engineer the make of your (current) broken boiler.

Are heat pumps a thing? 🤔

We think so. Read about the best combi boilers vs. heat pumps here.

Summary

If you’re picking a boiler from this list, you can’t go far wrong. Just don’t drift too far right – that never ends well.

You can calculate the size of boiler you need here, with a fixed price. If you don’t live offshore, we’ll likely even have a local engineer to fit it this week.

If you’re using another company or independent engineer, our prices can still be used as a barometer, and you’ll be armed with that knowledge plus what combi boiler and size of boiler you need.

Get your quote.