Glow-worm boilers review

Glow-worm is owned by Vaillant, but it offers more budget-friendly options than the boilers made by its parent company.

While its customer score of 74% is lower than the likes of Vaillant and Worcester Bosch, it's comparable to other budget-friendly brands like Ideal and even higher than others like Potterton. 

But customer score only makes up 20% of the overall total. Our full analysis includes assessments of boiler reliability and a survey of what engineers really think about the gas boilers they install every day.

Only Which? members can access the full results of our survey. Log in now or join Which? to see if Glow-worm delivers on quality as well as price.

Glow-worm gas boiler scores

An impressive nine in 10 Glow-worm boiler owners are satisfied. Of that number, around four in 10 describe themselves as 'very satisfied', the highest rating possible. 

Not quite nine in 10 Glow-worm customers would recommend the brand to a friend, so that tracks a little lower than satisfaction. This is bang-on the average figure of likelihood to recommend their boiler to someone else. 

But this only represents 20% of the overall picture. Engineer ratings and reliability scores play a huge part in the final verdict.

Join Which? for access to all the details.

Glow-worm engineers' review 

We heard from 198 expert engineers who scored boiler brands on several tests. We asked them to score gas boiler brands on the following:

• The ease of sourcing spare parts. 
• How easy it so to change a common component (a heat exchanger).
• The ease of servicing the brand's boilers.
• The build quality of the brand's boilers.
• The quality of technical support provided by the manufacturer.
• Whether or not engineers would recommend the brand to consumers (we filter out incentivised and brand affiliated engineers).

We aggregate all of these scores and use them to create our overall engineers' score, which is 40% of our total brand score.

Which? members can see how engineers rated Glow-worm gas boilers on all of these tests by logging in, while others can sign up to Which? to unlock our full analysis.

Glow-worm gas boiler reliability

Boilers are major purchases you should only make once every 10 to 20 years. You can keep yours for longer if you get it regularly serviced and if you get faults fixed quickly.

We've asked people who bought a boiler in the past six years about whether it's fault-free. When faults are reported, we measure how serious the fault was, how long it took for the first fault to happen, and we make sure it was fixed by an engineer.

Using this data, Which? members can see which brands produce boilers that are less prone to fault than others.

See our guide to getting the best boiler service.

Log in now or join Which? to see the full results.

Glow-worm boiler costs

Combi boilers

Regular boilers

System boilers

How expensive are Glow-worm boilers?

Glow-worm is owned by Vaillant, which is a premium brand. However, Glow-worm offers more budget-friendly options than the boilers made by its parent company.

Where to buy Glow-worm boilers

It's easy to rush into making a decision, especially if your boiler breaks down in winter, but we recommend getting a couple of quotes from a qualified heating engineer and comparing costs. Our Trusted Trader service can link you up with vetted boiler installers in your area.  

You could also buy a boiler yourself and hire an installer. Before you go ahead, it's worth getting advice from an expert who can assess your current heating system and identify the type of boiler that meets your specific needs. If you buy a boiler without having an installer lined up, you could find yourself struggling to find someone willing to set it up for you. An installer may have access to trade or wholesale prices, and will be able to recommend a model based on a holistic assessment of your home and heating system.

Only a Gas Safe Registered engineer/installer can install a new boiler. It's both dangerous and illegal to do so yourself if you're not qualified. 

Where to buy a boiler – find out what your options are.

Are Glow-worm boilers efficient?

New boilers must be A-rated, but how efficiently your boiler works in practice depends on several factors, including how you use it and how well it's installed. Use a Which? Trusted Trader for your boiler installation and regular maintenance.