Viessmann 025-W Review: The Best Budget Boiler?

Boilers. Unseen. Unloved. Unappreciated. Until they break.

Then suddenly, it’s like losing a limb, and you realise just how important they are to your very existence. If your old boiler is wheezing like a 40-a-day smoker on a marathon start line, and you need a reliable, budget-friendly replacement, the Viessmann 025-W could be the unsung hero you’re looking for.

But does it actually deserve a place in your home, or is it just another budget boiler destined for an early grave? Let’s tear it apart and find out. In this Viessmann 025-W review, we’ll go deep into technical specs, warranty details, property suitability, and how it stacks up against other budget boilers like the Worcester Bosch 1000 and Glow-worm Compact.

If you’d prefer to watch, then read, we got’chu:

…Who’re Viessmann?

Like most people, if you’ve never heard of Viessmann, you might assume they’re some newcomer trying to break into the UK boiler market. But, that couldn’t be further from the truth.

Founded in 1917, Viessmann is one of the largest boiler manufacturers in Europe. This German engineering powerhouse produces some of the most efficient, durable, and reliable boilers on the market. Their commercial heating systems power everything from hospitals and universities to skyscrapers, while their domestic range is designed to bring that same level of precision and quality to your home.

Viessmann has become a dominant force in the UK, winning multiple Which? Best Buy awards, gaining recognition for their outstanding reliability and efficiency, and offering some of the best warranties available. They also prioritise eco-friendly heating solutions, including hydrogen-ready boilers and renewable heating technology.

Viessmann 025-W Tech Specs Reviewed

Unlike most budget boilers that come with a cheese-grade aluminium heat exchanger, the Viessmann 025-W rocks a stainless steel one, which means it lasts longer, corrodes less, and handles heat like an absolute champ.

Want to know why heat exchangers are make or break? Check out our heat exchanger guide.

Other Than a Silly Name, What Makes the Viessmann 025-W Stand Out?

1. Stainless Steel Heat Exchanger

Heat exchangers are the heart and soul of any boiler. They transfer heat from the burner into the water, and in budget boilers, this is where manufacturers cut costs. Most cheap boilers use flimsy aluminium heat exchangers, which degrade faster, corrode easily, and have shorter lifespans.

But not the Viessmann 025-W. This beauty comes with a stainless steel heat exchanger, which is stronger, more resistant to corrosion, and offers superior longevity. If you want a boiler that actually lasts, this is the feature to care about most.

2. 92% Efficient– Helps Save The Planet, So You Don’t Have To

A boiler’s efficiency rating tells you how much energy it converts into actual heat. The Viessmann 025-W is ErP A-rated with a 92% efficiency, meaning less wasted energy, lower gas bills, and fewer tears when your winter heating bill arrives.

Want a boiler that will make your wallet and the planet happy? See our list of the most efficient boilers.

3. Compact Design – Fits Anywhere

At just H 700mm x W 400mm x D 300mm, the Viessmann 025-W is small enough to fit in a kitchen cupboard. If space is at a premium, you won’t need to worry about finding a bulky storage area for this unit.

Not sure if a combi is right for your home? Read our combi vs. system boiler guide.

Comparisons to Other Brands

There’s other budget boilers on the block, so, how does the Viessmann 025 stack up compared to other popular options, like the Worcester Bosch 1000 or the Glowworm Compact?

If you’re after more power and performance, we’d recommend you check out our reviews of the 025’s bigger brother, the Viessmann Vitodens 050-W. Or, it’s even bigger bigger brother, the Viessmann 100-W.

It doesn’t have a sister.

Viessmann 025-W vs. 050-W vs. 100-W: Which One Should You Choose?

Viessmann doesn’t do rubbish boilers. But not every Viessmann boiler is right for your home. Here’s how the 025-W stacks up against the 050-W and the 100-W.

Which Viessmann Boiler is Right for You?

Go for the Viessmann 025-W if:

• You want a no-frills, reliable boiler at a bargain price

• Have a flat, or smaller home with lower hot water demand

Go for the Viessmann 050-W if:

• You need a little extra oomph and have a busier home

• You want a longer warranty for peace of mind

Go for the Viessmann 100-W if:

• You want the best of the best

• You want improved efficiency and more power

• You have a larger home, with multiple bathrooms

• You want the longest warranty in the range

The Viessmann 025 Verdict

If you’re on a budget and want a new boiler that won’t croak after a couple of years, the Viessmann 025-W annihilates the competition. Its stainless steel heat exchanger means fewer breakdowns, fewer repairs, and less chance of your boiler throwing a tantrum in the dead of winter.

Plus, it’s backed by a massive brand, so if it ever breaks down, you won’t have a break down.

More Boiler Guides & Reviews

• Best Combi Boilers 2025

• Worcester Bosch 1000 Review

• Glow-worm Boilers Review

• New Boiler Costs: Explained

• Boiler Pressure Dropping Daily? Causes and Fixes