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Vaillant aroTHERM pro: published data, design caveats and the 11 kW weight problem
The Vaillant aroTHERM pro reached the UK in April 2026. We covered the wider family in our overview of Vaillant’s new anthracite aroTHERM range; this is the dedicated deep dive: the published data and whose data it is, why the sound figures are the wrong kind for a planning assessment, the weight conflict that decides whether an 11 kW can go on a wall, and the real warranty position.
- 7 min read
- Published 19 August 2026
THE AROTHERM PRO AT A GLANCE
Three UK sizes: VWL 55/7.1 A (5 kW) and VWL 75/7.1 A (7 kW) on 230 V single phase, VWL 115/7.1 A (11 kW) on 400 V three phase per vaillant.de. Available from April 2026; the 11 kW was preorder only, with market availability from 1 June 2026. R290, GWP 3 on Vaillant UK’s own figure.¹ Flow temperature 10–70 °C, 70 °C without a backup heater (Vaillant DE; Vaillant UK does not publish it). SCOP at 35 °C of 5.01, 4.87 and 4.93; at 55 °C, 3.70, 3.62 and 3.66 — all EN 14825, all Vaillant Germany, because Vaillant UK publishes no SCOP at all. Single fan across all three sizes, variable-speed pump, and a Flexible Space Function that shrinks the R290 exclusion zone — provided the unit is never switched off.
What the pro is, and what it is not
The pro is not a smaller aroTHERM plus in a darker jacket. It is deliberately simpler: three outputs against the plus range’s spread from 3.5 kW upwards, a single fan across all three sizes rather than twin fans at the top end, a smaller footprint, and — reported rather than published in UK literature — a variable-speed circulation pump where the plus runs a fixed flow rate. If that holds it is the more interesting difference: a modulating pump can hold a sensible ΔT instead of hunting.
What the pro does not have is a field record. Four months old here, no body of installer experience, no pattern of recurring faults — and we will not invent one. The only documented caveat is the Flexible Space Function power requirement below. Sizing is unaffected: the heat loss picks the machine, as our guide to what size heat pump you need sets out.
The SCOP figures — and whose figures they are
This is where a launch post quotes a big number and moves on. The problem is provenance. Vaillant UK publishes no SCOP for the pro at all — the UK material says only “ErP up to A+++”. Every seasonal figure here comes from Vaillant Germany’s technical data, tested to EN 14825.
On that data the 5 kW returns SCOP 5.01 at 35 °C and 3.70 at 55 °C; the 7 kW, 4.87 and 3.62; the 11 kW, 4.93 and 3.66. One inconsistency: Vaillant’s international site quotes a high-temperature SCOP range of 3.62–3.84, which does not reconcile with the German model-by-model figures. If someone quotes 3.84, ask which model and which document.
The 70 °C flow capability will get quoted at you too. It is a capability, not a design target — every degree above what the emitters need is efficiency given away. Our radiator output calculator shows the derating in a minute.
Sound power is not sound pressure
The published acoustic data is sound power: at A-7/W35 in 60% quiet mode, 48.2 dB(A) for the 5 kW, 49.9 dB(A) for the 7 kW and 55.1 dB(A) for the 11 kW. Maximum sound power day/night is 57.7 / 48.2 dB(A) for the 5 kW and 65.6 / 55.1 dB(A) for the 11 kW.
Legitimate figures, and they compare well. They are also not what an MCS 020 planning noise assessment runs on. That needs sound pressure at a stated distance, with directivity, and none is published for the pro — you cannot convert one to the other by eye. Third-party summaries quoting a single rounded figure for both the 5 and 7 kW do not match Vaillant’s own data either. On a tight plot, get the sound pressure data before committing to a position.
The 11 kW weight conflict, and the Flexible Space Function catch
The detail that matters most on the drawing board. Vaillant UK lists the 11 kW at 133 kg. Vaillant Germany lists it at 137.65 kg operating. Wall mounting is reported as rated to 135 kg. The unit sits on either side of that limit depending on which of the manufacturer’s own figures you believe — comfortably under it on the UK document, over it on the German one. That is not a rounding quibble; it is the difference between a compliant bracket and one you would not want to sign off. The 5 kW (84.5 kg) and 7 kW (90.9 kg) are nowhere near it. For the 11 kW, get written confirmation from Vaillant UK of the operating weight and mount rating before designing a wall installation — or put it on ground feet.
The Flexible Space Function is the other headline. Standard R290 practice is a 1 m clearance in all directions free of ignition sources; FSF runs the fan continuously at low speed in standby to disperse any leak, shrinking that zone to roughly the area directly below and behind the unit — which is what permits siting near doors, windows and cellar shafts. Vaillant UK calls it only “a minimal protection zone” and does not publish the geometry, so read the installation manual.
The caveat, reported rather than published: with FSF active, the outdoor unit must stay powered on at all times. Fine for a machine running year-round; less fine for a homeowner who isolates it every May, or a void property switched off between tenancies. Say so at handover, in writing.
AROTHERM PRO — PUBLISHED SPECIFICATION (5 / 7 / 11 kW)
| 5 kW | 7 kW | 11 kW | |
|---|---|---|---|
| UK model ref | VWL 55/7.1 A | VWL 75/7.1 A | VWL 115/7.1 A |
| Supply | 230 V 1-ph | 230 V 1-ph | 400 V 3-ph (per vaillant.de) |
| SCOP 35 °C (EN 14825, Vaillant DE) | 5.01 | 4.87 | 4.93 |
| SCOP 55 °C (EN 14825, Vaillant DE) | 3.70 | 3.62 | 3.66 |
| ErP class 35 / 55 °C | A+++ / A++ | A+++ / A++ | A+++ / A++ |
| Rated heat output A7/W35 ΔT5K | 3.36 kW | 4.48 kW | 7.53 kW |
| Max heat output A-7/W35 | 4.84 kW | 6.37 kW | 11.12 kW |
| Refrigerant charge (R290) | 0.5 kg | 0.6 kg | 1.05 kg |
| Sound power, A-7/W35, 60% quiet | 48.2 dB(A) | 49.9 dB(A) | 55.1 dB(A) |
| H×W×D (mm) | 750×1104×454 | 750×1104×454 | 1103×1169×454 |
| Weight (operating) | 84.5 kg | 90.9 kg | 137.65 kg (DE) / 133 kg (UK) |
Flow temperature 10–70 °C. Operating ambient: heating −25 °C to +43 °C, DHW −22 °C to +44 °C.
¹ GWP 3 is Vaillant UK’s published figure for R290 and the AR4 value still used by the EU F-Gas Regulation. IPCC AR6 (2021) puts propane’s 100-year GWP at 0.02, the figure Vaillant international quotes.
Warranty and certification — read the small print
The warranty story is not a pro-versus-plus difference. Vaillant UK runs a tiered scheme: 2 years standard; up to 5 years with myREWARDS registration, but only for Gold, Platinum or Renewable Partner installers, with Silver getting 3; and 7 years only where a Vaillant hot water cylinder is fitted by a Renewable Partner or Platinum member. Guarantee length is decided by who installs it and what cylinder goes with it — not by which aroTHERM you chose. Also: Vaillant UK’s guarantee page lists the aroTHERM and aroTHERM plus but does not yet name the pro, and the pro product page states only “Standard 2 year warranty”. Get that confirmed in writing.
On MCS: we could not verify a listing for VWL 55/7.1, 75/7.1 or 115/7.1, and found no Heat Pump Keymark certificate for any pro model. That is not evidence of absence — the directory is client-side rendered and blocked to us — but we will not state certification we cannot confirm. Check the MCS Product Directory for your exact model reference.
DESIGNER'S INSIGHT
“The number I keep coming back to isn’t the SCOP, it’s 137.65 against 133 against a 135 kg wall-mount rating — two manufacturer figures for the same machine, landing either side of the limit. That’s a two-and-a-half kilo argument deciding whether an 11 kW goes on a bracket or on the ground, and exactly the sort of thing that surfaces on site at eight on a Tuesday. The performance data is genuinely good; 5.01 at 35 °C is a strong low-temperature number. But good data doesn’t excuse missing data — no UK SCOP, no sound pressure at a stated distance, no settled weight. Ask for all three in writing, and design from the answers rather than the brochure.”
Phil
Founder & Lead Designer, Heat Loss Hub
A designer's honest take
Heat Loss Hub is independent — we hold no Vaillant account, take no manufacturer incentives, and do not install. Read this as engineering commentary, not endorsement.
The pro looks well judged for its target market: compact, R290, an exclusion-zone strategy that opens up difficult positions, and EN 14825 numbers that stand up. The reservations are about documentation, not engineering — German test data doing UK duty, sound power where MCS 020 wants sound pressure, a weight stated two ways either side of the limit. Not a bad machine. Just one you should not specify from a brochure.
When a Vaillant unit wins a place in one of our designs it will be because the tables read best at your conditions — and when a rival’s read better, the rival goes on the drawing instead. If you want that done properly, start your design journey and we will work it up from your heat loss.
CONTENTS
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