NIBE S2125: A Review

I’ve always believed that choosing a heat pump should never be about trends or headlines.

Instead, it’s always been about:

• Proven engineering
• Long-term reliability
• Real-world performance in cold climates.

That mindset is exactly why we have recently added the NIBE S2125 range as the premium air source heat pump option at Geowarmth.

Background: NIBE’S latest models

Our decision followed NIBE’s introduction of two larger output models to the S2125 range. 

As a result, the S2125 can now comfortably serve a much wider variety of homes across the North East of England. This ranges from well-insulated new builds to larger, older properties.

It’s also the same heat pump I have installed in my own home.

Reasons to choose the NIBE S2125

1. It’s designed for Sweden

Not all heat pumps work well in cold weather.

However, the NIBE S2125 is designed and built in Sweden, specifically for harsh Scandinavian winters.

Because of that, it performs exceptionally well in UK conditions. 

In fact, it’s ideally suited to the colder, windier climate we experience across Northumberland, Newcastle, Durham, Sunderland and Teesside.

Put simply: if a heat pump can handle Swedish winters, it will cope comfortably with anything the North East throws at it.

2. It’s designed in Sweden

Sweden is famous for the quality and safety of its manufacturing.

(This is the nation that invented the modern ‘v-shaped’ seatbelt and then released its patent for free!)

The S2125 is no exception.

Unlike many competitors, it’s designed, built and tested in Sweden, i.e., not outsourced and then given a badge at the end.

Having previously worked for NIBE, I’ve visited the Swedish factory several times.

I’ve seen first-hand the level of engineering that goes into each heat pump, from component selection to assembly, testing and final quality control. 

Every unit is thoroughly tested before it ever leaves the production line, ensuring it performs exactly as intended in real-world conditions.

In short, the build quality of the S2125 is exceptional. From the casing to the internal components, everything feels robust, well thought out and built to last. 

This is not a heat pump designed to scrape through a warranty period. Instead, it’s engineered for decades of dependable operation in demanding climates.

3. It uses natural refrigerant R290

Another major reason we at Geowarmth rate the S2125 so highly is its use of R290 (propane), a natural refrigerant with an extremely low global warming potential.

NIBE has decades of experience using R290, so this isn’t untested technology.Because of R290’s properties, the S2125 can:

• Operate extremely efficiently
• Achieve higher flow temperatures
• Deliver faster hot water recovery
• Work with smaller radiators than many traditional heat pump systems

That said, good system design still matters. 

For that reason, at Geowarmth we always aim to design radiators and emitters to operate at the lowest reasonable flow temperature, maximising efficiency and comfort.

4. Its unique safety design makes installation much easier

One feature that truly sets the S2125 apart is its enhanced safety design.

Unlike other R290 heat pumps, the S2125 does not require a large protective zone around the unit. Consequently, siting the heat pump is far easier.

This is especially valuable for:

• Terraced homes
• Smaller gardens
• Urban properties
• Tight access locations

Heat pump installation timelines can vary. But for the S2125, there’s more flexibility for installation times than most competing heat pumps on the UK market.

5. NIBE have expanded their range

Originally, the S2125 range covered smaller outputs. However, two larger output models have now been added.

As a result, the range now includes four single-fan models:

• S2125-8 – 5kW
• Up to S2125-20 – 12.5kW

Because of this expanded output range, we can now confidently specify the S2125 for a far wider variety of properties. That is precisely why we have now added it to our air source heat pump offering at Geowarmth.

6. It has a single-fan design

Notably, every S2125 model uses a single-fan design, even at higher outputs.

By contrast, many competitors rely on tall, double-fan units at 10–12kW. This leads to several advantages:

• Better aesthetics
• Lower visual impact
• Quieter operation
• Easier integration into residential settings

This makes the S2125 particularly well suited to towns and villages across the North East.

7. It is larger by design

At first glance, the S2125 appears physically larger than some competitors.

However, this is entirely intentional…

The internal layout allows for excellent airflow management, which significantly reduces the heat pump’s noise. As a result, the S2125 is one of the quietest air source heat pumps available.

• Sound levels start at just 49dB
• Comparable to light rainfall
• Ideal for closely spaced homes and quiet neighbourhoods.

In practical terms, it’s a heat pump you’ll barely notice.

8. It has a subtle, modern appearance

Visually, the S2125 is finished in a soft light grey, helping it blend naturally into its surroundings. Whether installed against brick, stone or render, it doesn’t dominate outdoor space.

For many homeowners, this is an underrated but important benefit.

9. Its SMO S40 controller

The SMO S40 controller is another standout feature.

Although it’s one of the most advanced controllers on the market, it remains extremely easy to use. That balance is rare.

Key benefits include:

• Full colour touchscreen
• Clear, intuitive menus in full English (other languages available)
• AI-based learning
• Automatically adapts to how your home heats and cools.

Over time, the system fine-tunes itself to deliver better comfort and efficiency, without constant user input.

9. App control and professional monitoring

In addition, the free NIBE app allows homeowners to:

• Monitor system performance
• Adjust temperatures remotely
• Check hot water availability
• Track efficiency

Furthermore, as a NIBE Pro Partner, Geowarmth can add your system to our professional monitoring portal.

This means we can often identify and resolve issues remotely before they become problems.

Why I chose the S2125 for my own home

If you’re looking for a premium air source heat pump, designed for cold climates, quiet operation, flexible siting and long-term efficiency, the NIBE S2125 stands out for all the right reasons.

This isn’t just theory for me.

I have a NIBE S2125 installed at my own home. Having previously worked for NIBE, I know the product range in detail.

I understand the engineering, the long-term performance, and how it compares to other heat pumps on the market.

Because of that experience, the S2125 was the only choice I considered.

You can read the full case study of my own NIBE S2125 installation on the Geowarmth website.

Installing premium air source heat pumps across the North East

At Geowarmth, we design and install air source heat pumps across:

• Newcastle upon Tyne
• Darras Hall
• Gateshead
• Sunderland
• Durham & Durham City
• Wynyard
• Northumberland
• North Tyneside & South Tyneside
• North Yorkshire
• Cumbria
• Scottish Borders
• Teesside & Darlington.