WPL 25 ACS
14.5 kW heating output, designed for larger properties (4-bed+) or properties with higher heat demand. Cooling-via-reverse-cycle option available, dual heating and DHW operation
Stiebel Eltron Air Source Heat Pumps
Stiebel Eltron is a renowned German manufacturer with over 40 years of specialist heat pump engineering experience. Their inverter mono-block heat pumps are the ultra-premium tier of our range, particularly strong for larger properties, complex installations, and customers who want the highest engineering specification regardless of price point. Effective operation down to -25°C, industry-leading acoustic performance, and a 7-year warranty extendable to 10 years.
For customers specifying premium German engineering above all other factors, Stiebel Eltron is the right call. We install three current models: the WPL 25 ACS (high capacity), the WPL A07 HK 230 Premium (cold climate specialist), and the latest Black Premium Range (Stiebel’s newest design generation).
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- German manufacturer, 40+ years of specialist heat pump engineering
- Stiebel Eltron is the heat-pump-first brand of our three: their entire product range across decades has been built around renewable heating.
- Operating range
- Down to -25°C ambient temperature, the deepest cold-weather specification in our range. Genuine relevance for properties in colder microclimates (Pennine valleys, exposed Scottish-border locations) and for customers who simply want maximum headroom.
- Typical SCOP we install at
- ~4.0 to 4.5 (~400-450% efficiency) on the WPL 25 ACS, with the Premium and Black Premium ranges achieving up to ~5.0 in optimised installs.
- Acoustic performance
- 32 dB(A) at 5 metres, the quietest in our range. For comparison: 32 dB at 5m is genuinely quieter than a whisper at 1m.
- Max flow temperature
- Up to 65°C, with low flow temperatures of 35°C maintained even at -10°C outdoor temperatures (a key SCOP-protecting capability).
- Warranty
- 7-year manufacturer product warranty as standard, extendable to 10 years through Stiebel Eltron’s extended warranty programme. Plus our 5-year workmanship guarantee on top.
- Refrigerant
- Model-dependent, with the Premium range using R454C (mid-low GWP) and newer Black Premium Range models using R290 (lowest GWP). We confirm refrigerant choice during your survey.
- Indicative pricing after BUS grant
- Typically £1,500 to £3,000 above the equivalent Clivet, reflecting the German engineering premium and feature set.
What makes Stiebel Eltron different in our range
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1.Heat pump specialist (not a generalist boiler manufacturer pivoting)
Vaillant and most of Clivet’s heritage sit in the broader heating/HVAC space. Stiebel Eltron has been heat-pump-first for decades, with engineering depth specifically tuned to heat pump applications.
For customers who specifically value “the company that has been doing this longest, with no distractions”, Stiebel Eltron is the strongest fit in our range.
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2.Deepest cold-weather operating range
The Stiebel Eltron range operates effectively down to -25°C ambient temperature, vs -20°C for Clivet and Vaillant. For most UK installs this is academic (East Anglia rarely goes below -10°C even during cold snaps). For properties in colder regional microclimates, or for customers wanting maximum specification headroom, the extra 5°C of operating range matters.
The cold-weather performance is achieved through Stiebel Eltron’s variable-speed inverter compressor architecture plus their specific R454C and R290 refrigerant chemistry choices.
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3.Industry-leading acoustic performance
Stiebel Eltron heat pumps run at 32 dB(A) measured at 5 metres, the quietest specification in our range. For context, 32 dB at 5m is genuinely below the threshold of a quiet conversation, well below the noise of a domestic fridge, and effectively imperceptible in a typical garden setting.
For customers with neighbour-window proximity concerns, bedrooms above the planned outdoor unit position, or particular noise sensitivity, this is a meaningful advantage.
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4.The Premium ranges (WPL A07 HK 230 Premium and Black Premium)
The Premium ranges are Stiebel’s flagship specifications. Key technical advantages over the standard WPL 25 ACS:
- Higher SCOP: Premium models achieve up to ~5.0 (~500% efficiency) in optimised installs
- R454C refrigerant (on WPL A07 HK 230 Premium): mid-low GWP, future-proof against current and forecast F-Gas regulations
- R290 refrigerant (on the newest Black Premium Range): lowest GWP available, fully future-proof
- High flow temperatures maintained at very low outdoor temperatures: the inverter unit achieves high flow temperatures even at -25°C, supporting strong cold-weather SCOP
- Suitable for new build and modernisation: equally strong fit for the latest super-insulated builds and for retrofit on older properties with higher heat loss
The Premium ranges sit above the WPL 25 ACS in our pricing. We recommend them when the customer specifically wants the highest specification or has a property profile (larger heat loss, complex zones, particular performance requirements) that justifies the premium.
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5.The Black Premium Range (newest generation)
Stiebel Eltron’s newest design generation, with redesigned aesthetics (black exterior finish, slimmer profile), updated R290 refrigerant chemistry, and enhanced acoustic performance. Suitable for customers who want the latest generation of Stiebel engineering and whose property aesthetics suit the black-finish exterior.
We are among the early UK installers of the Black Premium Range; spec sheet details are still evolving as the range builds out, and we confirm exact specification on your bespoke proposal.
The Stiebel Eltron range we install
WPL A07 HK 230 Premium
7.5 kW heating output, ideal for 2-3 bed properties with R454C refrigerant and very strong cold-climate specification
Black Premium Range
Newest generation, R290 refrigerant, multiple output sizes covering 5-15 kW typical demand
All installs include a Stiebel-recommended hot water cylinder sized to your household and the Stiebel Eltron app for monitoring and control.
How Stiebel Eltron compares to our other brands
| Spec | Clivet (Our top pick) | Vaillant | Stiebel Eltron |
|---|---|---|---|
| Greenscape positioning | Our top pick for most homes | Mid-tier, retrofit-friendly | Ultra-premium German engineering |
| Manufacturer origin | Italian (decades of HVAC heritage, dedicated UK HQ) | German (long-established UK service network) | German (40+ years specialist heat pump experience) |
| Refrigerant | R290 (low GWP, future-proof) | R290 (low GWP, future-proof) | R454C or R290 (model-dependent) |
| Compressor type | Variable-speed inverter | Variable-speed inverter | Variable-speed inverter |
| Typical SCOP we install at | ~4.6 (with Adia Thermal) | ~4.0 to 4.5 | ~4.0 to 4.5 (up to ~5.0 on Premium range) |
| Equivalent efficiency | ~460% | ~400-450% | ~400-450% |
| Max flow temperature | Up to 75°C | Up to 75°C | Up to 65°C |
| Operating range | Down to -20°C ambient | Down to -20°C ambient | Down to -25°C ambient |
| Acoustic performance | 40-44 dB(A) at 1m | 48 dB(A) at 1m (Quiet Mark accredited) | 32 dB(A) at 5m (quietest in our range) |
| Smart control system | Adia Thermal Control System (exclusive Clivet integration, real-time SCOP visibility, e-SCOP boost on smart tariffs, room-by-room scheduling) | myVAILLANT app | Stiebel Eltron app |
| Manufacturer warranty | 7 years with MCS install (some models 10 years) | 2 years standard, extendable to 7 years free when registered through our installer status | 7 years standard, extendable to 10 years |
| Greenscape workmanship guarantee | 5 years on every install (same on all three brands) | 5 years on every install | 5 years on every install |
| Best for | Most homes, best balance of efficiency, value, and smart control | Customers prioritising high flow temperature (less radiator upgrade work), or wanting the Vaillant brand they trust from their previous boiler | Larger/more complex properties, properties in colder microclimates, customers specifying premium engineering above all |
We recommend Clivet as the default for most homes because the Adia Thermal Control System integration delivers the strongest real-world SCOP at the lowest install cost across our range.
We recommend Vaillant when the customer has retrofit-specific constraints (older radiators, existing Vaillant boiler ecosystem) or values Quiet Mark accreditation.
We recommend Stiebel Eltron when:
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The property is in a colder regional microclimate or the customer wants the deepest cold-weather operating specification
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The customer specifies premium German engineering above other considerations
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Acoustic performance is a deciding factor (the 32 dB at 5m figure is genuinely class-leading)
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The customer wants the newest generation (Black Premium Range)
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The property is larger or more technically complex (5+ bedrooms, multiple heating zones, dual underfloor + radiator system)
Pricing context
Stiebel Eltron sits at the premium tier of our range, reflecting the German engineering premium and Premium range feature set.
| Property | Typical Stiebel model | After BUS grant (mains gas / electric) | After BUS grant (£7,500) |
|---|---|---|---|
| 2-3 bed mid-range | WPL A07 HK 230 Premium | From £8,495 | From £6,995 |
| 3-4 bed standard install | WPL 25 ACS | From £9,495 | From £7,995 |
| 4-5 bed premium spec | WPL 25 ACS or Black Premium Range | From £10,495 | From £8,995 |
| Larger / complex | Bespoke Stiebel configuration | From £12,000 | From £10,500 |
All prices include the Stiebel Eltron app controls and the recommended high-gain hot water cylinder. Every install is bespoke after a free heat loss survey. Zero VAT on the entire install. Finance available through Greenscape Energy.
Our reviews speak for themselves
Trustpilot
Friendly and efficient service from Cloe!
Pa 31 Oct 2026
Trustpilot
The two technicians, Luke & Cam arrived as scheduled, were courteous and respectful. They carried out the work as requested and invited me to inspect what they had done. Luke also clarified and guided me through a particular aspect on the Solis App.
V Evans 30 Oct 2026
Trustpilot
As usual, Greenscape customer service resolved my query quickly and professionally. I had a query about winter settings for my batteries which Chloe resolved for me and then sent a follow up email to confirm all is in place. Thank you!
Hayley Goldson 30 Oct 2026
Trustpilot
Harry fixed a persistent problem we've had for years. Over the last 4 years, a number of engineers had a go at fixing this but without success. Very happy with Harry and the knowledge he had of the Mitsubishi system
Eric Henderson 30 Oct 2026
Trustpilot
Can’t thank Chloe Hickman enough for sorting out my winter charging so quickly and efficiently Stephen Carpenter
Stephen Carpenter 30 Oct 2026
Trustpilot
Excellent service given by our Greenscape engineer Harry, who sorted our heating and gave a detailed explanation of the problem
customer 30 Oct 2026
Trustpilot
Darren Ben and Cameron were absolutely lovely very helpful and professional. Neat and tidy and really nice guys, great job done very happy
Laura Lawrence 29 Oct 2026
Trustpilot
Aaron at Greenscape Energy provided a prompt, friendly, informative and helpful service when quoting the proposed PV and battery system for our property.
M Hayes 29 Oct 2026
Trustpilot
Both Brandon and young apprentice Ellis arrived on time to install my long awaited Pylontech battery. What can I say, they were very smart, professional and most polite. Greenscape have a good team here, please retain them and do pass on my best regards to them both. Cheers Paul
MRS MARILYN BAILEY 29 Oct 2026
Trustpilot
Chloe was very helpful with my winter settings, my app wasn’t the same as the written instructions but she just did it for me and then checked to see it was all working correctly.
Ruth 28 Oct 2026
Google I have used Greenscape Energy to install Solar Panels and Tesla Powerwall batteries and I can confidently state that they are an excellent company to deal with. I recently had a minor problem with the batteries not being charged during the cheap rate. Greenscape could not have been more helpful and put me in contact with Tesla to resolve the problem. Fantastic service from a professional company.
Tim Reid 27 Oct 2026
Google Michaela, dealt with my finance query in a professional, efficient manner, and placated my fears that the progress on my solar system would be paused until the return of the surveyor from holiday. Good customer care. Thank you
Andrew Kay 16 Sept 2026
Google Very professional and efficient from the sales engagement through to commissioning. I wouldn’t hesitate in recommending them.
Granary Barn 17 Aug 2026
Google I have been very impressed with the service I received from Greenscape. The initial survey was very professionally done by Andrew and I was pleased that he convinced me not to have more panels than necessary. The team that installed the battery and inverter were excellent and very pleasant to deal with. The system is up and running and there have been no complications. I thoroughly recommend Greenscape.
Richard Stainer 11 Aug 2026
Google I arranged to have solar panels and a battery installed by Greenscape via OVO Energy. From start to finish, the service has been excellent. From the survey, to the panel installation and battery installation, every team member has been professional and very friendly. The after sales have kept in contact to make sure everything has gone smoothly. Couldn't fault Greenscape.
Gareth 7 Jul 2026
“I would certainly recommend renewables! — Greenscape also handled the old oil tank removal, which made it a lot easier.”
Common questions about Stiebel Eltron
01 Is Stiebel Eltron worth the premium over Clivet?
For most homes, no. Clivet + Adia Thermal delivers a typical SCOP of 4.6 versus 4.0-4.5 on Stiebel Eltron standard models, and the install cost is £1,500-£3,000 lower. The Stiebel premium is worth it when you specifically need premium-tier engineering (very large property, complex install, very cold microclimate, acoustic-sensitivity, or the Black Premium aesthetic).
02 What is the warranty really?
7-year manufacturer warranty standard, extendable to 10 years through Stiebel Eltron’s extended warranty programme. Plus our 5-year workmanship guarantee on the install itself. Practical total: up to 10-year manufacturer + 5-year workmanship.
03 What is the difference between WPL 25 ACS and the Premium ranges?
The WPL 25 ACS is Stiebel’s high-capacity standard model (14.5 kW). The WPL A07 HK 230 Premium is a smaller (7.5 kW) but more specified unit with R454C refrigerant and very strong cold-weather operation. The Black Premium Range is the newest design generation with R290 refrigerant. We recommend the right model based on your property heat loss survey.
04 Does Stiebel Eltron integrate with smart tariffs?
The Stiebel Eltron app supports time-of-use scheduling for hot water cylinder heating and zone schedules. Less automated than Adia Thermal on Clivet installs, but the basic capability is solid.
05 Does Stiebel Eltron integrate with my solar/battery?
Yes. The Stiebel Eltron app and controls support integration with smart home energy management systems. If you have or are adding a Greenscape solar and battery setup, we configure the integration during commissioning.
06 Why is the 32 dB acoustic figure measured at 5 metres rather than 1 metre?
It is genuinely how the unit measures, but it is a fair question because it is harder to compare directly with the 40-48 dB figures other manufacturers quote at 1m. Converting roughly: 32 dB at 5m is approximately equivalent to 46 dB at 1m, similar to Vaillant’s 48 dB at 1m. The Stiebel acoustic engineering is genuinely strong, but the 5m measurement convention makes direct comparison harder.
Ready to talk?
A free survey assesses whether Stiebel Eltron is the right brand for your home, models the savings against your current heating system, and gives you a bespoke proposal with itemised costs and finance options.
Or call us directly on 01473 727 727
Showroom:
The Energy Shop, 544–550 Woodbridge Road, Ipswich, IP4 4PN.
Open 8am to 5:30pm Monday to Thursday, 8am to 4:30pm Friday. Closed at weekends.
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