When comparing Glow-worm and Viessmann boilers, the better choice depends on your budget and what you value most. Glow-worm is a strong option if you want a reliable, affordable boiler that offers good value for money.
Viessmann may be more appealing if you prefer premium German engineering, a stainless steel heat exchanger and a more refined design. Both brands offer A-rated condensing boilers with good energy efficiency and established support networks in the UK.
Glow-worm is a British heating brand that has been manufacturing heating appliances in Belper, Derbyshire, since the 1930s. It is now part of the Vaillant Group. Viessmann, meanwhile, is a German family business founded in 1917, with its heating division becoming part of American company Carrier Global in 2024.
At Guscott Heating, our Gas Safe registered engineers install both brands in homes across Kent and the South East, from Maidstone and Canterbury to Tunbridge Wells, Bromley and Brighton. This guide compares Glow-worm and Viessmann boilers side by side, covering their costs, efficiency, reliability, warranties and performance to help you choose the right option for your home or rental property.
Glow-worm vs Viessmann Boilers: Key Facts
Glow-worm and Viessmann both offer efficient, dependable boilers, but they cater to different budgets and priorities. Glow-worm stands out for its affordability and value for money, while Viessmann focuses on premium engineering and build quality. The table below compares their key features side by side.
| Factor | Glow-worm | Viessmann |
| Origin and ownership | British, made in Belper, Derbyshire; part of the Vaillant Group | German, founded 1917; heating division owned by Carrier Global since 2024 |
| Boiler price (unit only) | Around £700 to £1,500 | Around £900 to £2,000 |
| Typical installed cost | Around £2,000 to £3,500 | Around £2,300 to £4,000 |
| Efficiency | ErP A rated, around 92% to 94% | ErP A rated, around 92% to 94% |
| Performance | Steady, dependable heating and hot water | Smooth, quiet running with strong hot water flow on larger models |
| Reliability | Good; simple design and widely available parts | Very good; known for durable build quality |
| Heat exchanger | Built for value and easy servicing | Viessmann’s own stainless steel design, known for long life |
| Warranty | Up to around 10 to 12 years, depending on model and installer | Up to around 10 to 12 years, depending on model and installer |
| Popular models | Energy, Ultimate3, Betacom 4 | Vitodens 050-W, 100-W, 111-W, 200-W |
| Boiler types | Combi, system and regular | Combi, system, regular and storage combi |
| Smart controls | Glow-worm smart thermostats and app controls | ViCare app and smart thermostats |
| Noise | Quiet in normal use | Very quiet in normal use |
| Parts and servicing | Parts easy to find; most engineers know the brand | Good UK support; parts can cost a little more |
| Best for | Budget conscious homeowners and landlords | Homeowners wanting premium quality and longevity |
Prices are guide figures for a straight swap in Kent and the South East, including fitting, a system flush, a magnetic filter and basic controls. Moving the boiler or changing its type will add to the cost.
Need a new boiler fitted? Guscott Heating provides boiler installation across Kent and the wider South East of England, including Maidstone, Ashford, Sevenoaks, Medway, Dartford, Folkestone, Crawley and Guildford. Our Gas Safe registered engineers fit both Glow-worm and Viessmann boilers. Get in touch today for a free boiler estimate tailored to your home.
Glow-worm vs Viessmann Boilers: Which Is Better?
Choosing between Glow-worm and Viessmann depends on your budget and what you expect from your new boiler. Glow-worm is a strong option if you want reliable heating at an affordable price, while Viessmann may suit homeowners looking for premium engineering and build quality. Here is a closer look at what each brand offers.
Why Choose a Glow-worm Boiler
Glow-worm boilers are a popular choice because they offer dependable heating at a fair price. The brand has been part of British homes for decades, and being part of the Vaillant Group gives it access to the same engineering know-how as one of Europe’s biggest heating manufacturers.
The Glow-worm Energy range is the brand’s best seller, available as a combi, system or regular boiler. The Ultimate3 range adds extra features and longer warranty options, while the Betacom 4 is a no fuss, entry level combi that suits flats and smaller homes.
Most Glow-worm models are compact, so they fit neatly into a kitchen cupboard, which is handy in terraced homes in Gillingham, Margate or Hastings.
Pros & Cons of Glow-worm Boilers
| Pros | Cons |
| Lower purchase and installation cost | Feels less premium than top end brands |
| Made in the UK | Fewer high end features on budget models |
| Backed by the Vaillant Group | Entry level models have shorter warranties |
| Compact sizes for small spaces | Not quite as quiet as premium brands |
| Parts easy to find and most engineers know the brand | Fewer large output options for very big homes |
| Strong warranty options on Energy and Ultimate3 models |
Should You Choose a Glow-worm Boiler?
Choose a Glow-worm boiler if…
- You want a reliable boiler at a lower price
- You are a landlord replacing a boiler in a rental property
- You live in a flat or a small to medium home
- You like the idea of a boiler made in the UK
Do not choose a Glow-worm boiler if…
- You want the most premium build quality available
- You have a large home with high hot water demand, such as several bathrooms
- Very quiet running is a top priority
Why Choose a Viessmann Boiler
Viessmann boilers are chosen for their German engineering and long life. The company designs its own stainless steel heat exchanger, the part of the boiler that transfers heat to your water, and it is well known for standing up to years of use.
The Vitodens range covers every type of home. The Vitodens 050-W is the entry level model, the 100-W is the most popular choice in UK homes, and the 111-W storage combi suits homes that need more hot water at once. The 200-W is a premium option for larger properties.
Viessmann’s ViCare app lets you control your heating from your phone, which is great for busy households in Sevenoaks, Guildford or Tunbridge Wells.
Pros & Cons of Viessmann Boilers
| Pros | Cons |
| Premium German build quality | Higher purchase and installation cost |
| Long lasting stainless steel heat exchanger | Parts can cost more |
| Very quiet running | Top models are larger |
| Wide range including storage combis | Higher end features you may not need |
| ViCare app for smart control | Ownership changed recently, which may affect support in future |
| Strong warranty options with approved installers |
Should You Choose a Viessmann Boiler?
Choose a Viessmann boiler if…
- You want a premium boiler that is built to last
- You have a larger home or several bathrooms
- You plan to stay in your home for many years
- You want smart control through an app
Do not choose a Viessmann boiler if…
- You are working to a tight budget
- You only need a basic boiler for a small flat
- You are replacing a boiler in a rental property where upfront cost matters most
Glow-worm vs Viessmann Boilers: What Are the Key Differences?
Glow-worm and Viessmann boilers differ mainly in price, build quality, model range and component durability. Each brand has its own strengths, so the better choice depends on your budget and heating requirements. Let’s compare these key areas and identify which brand comes out on top in each category.
Origin and Ownership
Glow-worm has been a British heating name since the 1930s. Its boilers are still made in Belper, Derbyshire, and it has been part of the German Vaillant Group since 2001. Viessmann was founded in Germany in 1917 and was family owned for over a century. In 2024, its heating business was bought by Carrier Global, a large American heating and cooling company.
Both brands have strong backing, but Viessmann’s long history of making premium boilers gives it a slight edge in reputation.
Winner: Viessmann, for its long standing premium reputation.
Price
A Glow-worm boiler usually costs around £700 to £1,500 to buy, depending on the model and output. A Viessmann boiler usually costs around £900 to £2,000. On a like for like basis, Glow-worm is typically a few hundred pounds cheaper.
Winner: Glow-worm
Installation Cost
A straight swap with a Glow-worm boiler typically costs around £2,000 to £3,500 fitted in Kent and the South East. A Viessmann installation usually costs around £2,300 to £4,000. Labour costs are similar, so most of the difference comes from the boiler itself. Moving the boiler, converting from a regular to a combi or adding new radiators will push either price up.
Winner: Glow-worm
Efficiency
Both brands make ErP A rated condensing boilers with seasonal efficiency of around 92% to 94%. In England, all new gas boilers must reach at least 92% under the Boiler Plus rules, and both brands meet this comfortably. Swapping a 15 year old non condensing boiler, which may run at 70% to 80%, for either brand could cut your gas use noticeably.
Winner: Draw
Performance
Glow-worm boilers deliver steady, dependable heating and hot water that suits most small and medium homes. Viessmann boilers run very smoothly and offer stronger hot water performance on larger models, including the 111-W storage combi. That model keeps a small store of hot water ready, so two showers can run at once with less drop in flow.
Winner: Viessmann
Reliability
Both brands have good reliability records when fitted and serviced properly. Viessmann has a reputation for very durable build quality, while Glow-worm benefits from a simple design and parts that are easy to get hold of. Much of Kent and the South East has hard water, which can cause limescale to build up inside any boiler, so a scale reducer and magnetic filter are worth fitting whichever brand you choose.
Check the latest Which? boiler brand reliability scores before you decide.
Winner: Viessmann, by a small margin.
Heat Exchanger
The heat exchanger is the heart of a boiler and one of the most expensive parts to replace. Viessmann designs and makes its own stainless steel heat exchanger, which is known for resisting corrosion and lasting a long time. Glow-worm’s heat exchangers are built for value and easy servicing.
Winner: Viessmann
Warranty
Both brands offer warranties of up to around 10 to 12 years on selected models. Your exact cover depends on the model and whether an approved installer fits and registers it. Entry level models, such as the Glow-worm Betacom 4 and Viessmann Vitodens 050-W, usually come with shorter cover. To keep any warranty valid, your boiler needs an annual service by a Gas Safe registered engineer.
Winner: Draw
Model Range
Glow-worm keeps its range simple, with the Energy, Ultimate3 and Betacom 4 covering most homes. Viessmann offers a wider spread, from the budget 050-W to the premium 200-W, plus the 111-W storage combi for homes with high hot water demand.
Winner: Viessmann
Boiler Types
Both brands make combi, system and regular boilers, so either can replace almost any existing setup. Viessmann also offers a storage combi, a useful middle ground for larger homes that want combi convenience with better hot water flow.
Winner: Viessmann
Smart Controls
Glow-worm offers its own smart thermostats and app controls, which let you adjust your heating from your phone. Viessmann’s ViCare app is well regarded and can also show the boiler’s status, which helps your engineer spot problems early. Both work with a range of third party smart thermostats too.
Winner: Viessmann, by a small margin.
Noise
Both brands run quietly in everyday use. Viessmann boilers are often singled out by engineers and homeowners as especially quiet, which matters if your boiler sits in a kitchen, utility room or flat where you can hear it.
Winner: Viessmann
Parts and Servicing
Glow-worm parts are widely available and usually cheaper, and almost every heating engineer in Kent and the South East has worked on one. Viessmann has good UK support, but parts can cost a little more and fewer engineers specialise in the brand.
Winner: Glow-worm
Best Suited Homes
Glow-worm suits flats, terraced houses and small to medium homes, and it is a smart choice for landlords who want reliable boilers at a sensible price. Viessmann suits larger family homes, properties with several bathrooms and homeowners who plan to stay put for many years.
Winner: Draw. It depends on your home.
The Overall Winner
Viessmann wins more rounds on build quality, range and refinement, so it is the better boiler brand if your budget allows. Glow-worm wins on price, installation cost and easy servicing, which makes it the better value choice for most smaller homes and rental properties. Whichever you pick, a quality installation matters more than the badge on the front.
Ready to Get a Free New Boiler Estimate?
If you’re thinking about replacing your existing boiler, getting a quote is a good first step. Guscott Heating helps homeowners and landlords across Kent and the wider South East find the right replacement boiler for their property, taking into account heating requirements, hot water demand and budget.
Request your free new boiler estimate today.
Frequently Asked Questions
Are Glow-worm and Vaillant Boilers the Same?
Glow-worm and Vaillant boilers are not the same, although both brands belong to the Vaillant Group. They share some engineering expertise, but they are designed and priced differently. Glow-worm focuses on value, while Vaillant sits higher up the market.
How Long Does a Glow-worm or Viessmann Boiler Last?
A Glow-worm or Viessmann boiler typically lasts 10 to 15 years with an annual service. Many well maintained boilers keep going longer. Fitting a magnetic filter and scale reducer helps protect the boiler in hard water areas like much of Kent.
What Size Combi Boiler Do I Need?
Most homes need a combi boiler of around 24kW to 35kW. A flat or small terraced house with one bathroom usually needs 24kW to 28kW, while a three or four bed home with one or two bathrooms usually needs 30kW to 35kW. Larger homes may suit a system boiler or storage combi instead. Your engineer should check your water flow rate before choosing.
Can Glow-worm and Viessmann Boilers Run on Hydrogen?
Most new Glow-worm and Viessmann gas boilers can run on a gas blend containing up to 20% hydrogen. The UK has not yet decided whether hydrogen will be used for home heating, so this is a future proofing feature rather than something you will use today.
Can I Still Get a New Gas Boiler?
Yes, you can still get a new gas boiler. There is no ban on replacing an existing gas boiler in your home. Rules for new build homes are moving towards low carbon heating such as heat pumps, but homeowners and landlords can still swap an old gas boiler for a new efficient model.