What’s the Most Reliable Boiler You Can Buy in the UK?

My boiler broke down yet again last week, it’s the second time this winter I’ve had a problem that’s resulted in a loss of hot water.

Thankfully I could call upon the services of my trusted friend John, who works as a heating engineer.

My experience of the Glow Worm HX boiler range has not been good at all and it got me thinking; what is the most reliable boiler brand in the UK?

I probed John with a few questions while he was here and for good measure, I also emailed another friend of mine, Paul, who is a Gas Safe registered installer.

I figured that if Paul was replacing broken boilers all day every day, he’d also have a good idea of which brand is breaking down the most.

Here are the questions I asked:

What do you think of Glow Worm HX boilers?

Which boilers are the most reliable?

Which ones are the easiest to repair?

What boiler would you recommend to a friend or close family member?

I was a little surprised when both my friends gave me almost identical answers to all these questions.

I guess if you’re working in the trade, you get to know these products very well and get a feel for what’s good and what’s not.

What do You Think of Glow Worm Boilers? Are They Reliable?

Paul – You get what you pay for with Glow Worm, their products are at the low-end of the price scale and as a result, they aren’t the most reliable. They’re normally fairly easy to repair though and unlike some other systems, you’ll usually only need to replace the one part to resolve the issue. Spare parts cost peanuts and you can get them anywhere.

John – I have a regular client who has had nothing but problems with her Glow Worm HX boiler, at least one call out per year for the last 5 years. This isn’t a one-off as Glow Worm are well known for being unreliable, but that’s what you get with a boiler you can buy off the shelf for less than £500. The only things I like about Glow Worm is their size – they’re tiny and perfect for small kitchens, and also how easy they are to maintain. A service can be done in 10 minutes.

Which Boilers are the Most Reliable and Experience the Least Number of Breakdowns?

Paul – I get asked this question or a variation of it every couple of days so I’ll give you the same three brands that, based on my experience, are the most reliable. I’m sure if you asked another guy in the trade, you’d get three different brands so just take it as my opinion. Vailant, Potterton and Worcester Bosch seem to be the most reliable.

John – Worcester Bosch is easily the most reliable, they just seem to go on and on. Vailant isn’t bad either.

Which Ones are the Easiest to Repair When They Breakdown?

Paul – Fault checking is easy on the Glow Worm boiler and I rarely have issues fixing one of these. They break down all the time as they’re at the lower end of the quality scale but are a piece of cake to fix.

John – Vailant are well built and easy to repair. I’d also say Viessmann.

Which Boiler Would You Recommend to Friends or Family Members For Reliability?

Paul – Worcester Bosch or Potterton would be my suggestion. I would also advise them to get a boiler that has more capacity than the one needed for the size of the home. The more capacity the boiler has, the quicker your rads will heat up and it puts less strain on the boiler. Also, if you extend the home, perhaps with a loft conversion or a side extension, you’ll have plenty of capacity and won’t need to change the boiler.

John – Vailant or Worcester Bosch as they seem to be the most reliable brands.


Worcester Bosch, Vailant and Potterton are the three brands that get the thumbs up from John and Paul.

Of course, this isn’t exactly the most scientific examination of boilers but Paul and John’s advice is impartial, so you can take it at face value.

Related Pages

We have a few similar pages on our site that may interest you:

Discover how much it costs to service a boiler in the UK.

See how I fixed a common problem with my Glow Worm boiler.

Solutions for boilers with low-pressure problems.

See how much it costs to replace a typical boiler.

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