Glow-worm boilers review
Glow-worm offers cheaper boilers than a lot of competitors. Our latest boiler
survey reveals what owners and engineers really think of them
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 72% 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 such as 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 our full results. Log in now or join Which? to find out the best boiler brands and how Glow-worm boilers stack up against the competition.
Glow-worm gas boiler scores
| Best Buy | Reliability | Customer score | Overall engineer score | Ease of sourcing | Ease of replacing | Ease of servicing | Build quality | Manufacturer support | Unbiased recommendation | % Score |
|---|---|---|---|---|---|---|---|---|---|---|
From our May 2024 UK general public online survey of 10,028 people who are responsible for the maintenance of their boiler and our May-June survey of boiler engineers. This included 7,619 gas boiler owners, 1,387 electric boiler owners, 448 oil boiler owners and 230 Which? Trusted Traders boiler engineers. The Total score for all types of boiler ignores price and is based on: Reliability (40%) How many boilers bought in the past six years developed a fault, factoring in time until first fault and severity. Fault had to be repaired by a trained plumber or engineer. Engineer score (40%) Made up of 15% ease of sourcing parts, 15% ease of replacing common components, 15% ease of servicing, 10% manufacturer support, 20% build quality, 25% unbiased recommendations (barring incentivised engineers). Customer score (20%) How satisfied owners are and likelihood to recommend a brand. Sample size of customers (282). Best Buy threshold for gas boilers: 75%.
80% of Glow-worm boiler owners told us they were satisfied with the brand. It gets a four star customer score.
But this only represents 20% of the overall picture. Engineer ratings and reliability scores make up 80% of our final verdict.
Join Which? for access to all the details.
Glow-worm engineers' review
Only Which? members can see engineers' reviews of Glow-worm boilers.
We heard from 230 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 faults 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
| Boiler name | Sizes available (kW) | Standard warranty (years) | Extended warranty (years) | Price range (smallest kW output and biggest kW output) |
|---|---|---|---|---|
| Energy | 25; 30; 35 | 10 | 10 | £1,061 to £1,425 |
| Ultimate 3 | 30; 35 | 10 | 10 | £550 to £600 |
| Easycom 3 | 24; 28 | 5 | 5 | £469 to £501 |
| Compact | 24; 28 | 5 | 5 | £421 to £453 |
Regular boilers
| Boiler name | Sizes available (kW) | Standard warranty (years) | Extended warranty (years) | Price range (smallest kW output and biggest kW output) |
|---|---|---|---|---|
| Energy | 12; 15; 18; 25 | 10 | 10 | £892 to £1,082 |
| Ultimate 3 | 25 | 10 | 10 | £615 |
| Easycom 3 | 25 | 5 | 5 | £615 |
System boilers
| Boiler name | Sizes available (kW) | Standard warranty (years) | Extended warranty (years) | Price range (smallest kW output and biggest kW output) |
|---|---|---|---|---|
| Ultimate 3 | 25 | 10 | 10 | £550 |
| Easycom 3 | 25 | 5 | 5 | £430 |
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 Which? Trusted Traders 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.
Visit Glow-worm's website for more details about its boiler range.
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