The Vaillant aroTHERM Plus is the UK’s most talked-about air source heat pump – and for good reason. It’s the first mainstream ASHP to use R290 natural refrigerant, delivers up to 75°C flow temperatures for retrofit compatibility, and holds Quiet Mark certification on 4 out of 5 models. It ranks as our top pick in our best air source heat pumps roundup. We spent 10 hours reviewing specs, installer feedback, and real-world monitoring data to deliver this verdict.
The aroTHERM Plus range spans 3.5kW to 12kW output, covering the vast majority of UK homes from a small terrace to a large detached property. Its R290 refrigerant has a Global Warming Potential of just 3 – compared to R32’s GWP of 675 – making it the most environmentally responsible refrigerant choice currently available in a mainstream UK heat pump. Paired with A+++ energy ratings and an MCS-certified SCOP of up to 5.03, this is genuinely one of the strongest technical specifications on the market.
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- Industry-leading 5.09 SCOP efficiency rating on the 7kW and 10kW models - the highest of any residential heat pump in the UK, cutting annual electricity costs by 15-20% versus average 3.5 SCOP units
- R290 natural refrigerant with near-zero global warming potential (GWP 3) - future-proofed against F-gas phase-downs that will affect R32 and R410A competitors by 2030
- Flow temperatures up to 75C without backup heating - compatible with existing radiators in older properties, eliminating the £3,000-8,000 cost of upgrading to underfloor heating
- Quiet Mark certified on 4 of 5 models at 35-42dB - quieter than a library, important for terraced houses and properties with close neighbours or planning restrictions
- Net cost from £4,500 after the £7,500 BUS grant on the 7kW model - the 3.5kW and 5kW share the same physical unit (software-limited), so the 7kW is the first genuinely differentiated option
Key Specifications
The Vaillant aroTHERM Plus is available in 3.5-12kW outputs using R290 refrigerant (GWP 3), delivers a maximum 75°C flow temperature, and operates down to −25°C ambient.
The aroTHERM Plus range comprises five models. The two smallest (3.5kW and 5kW) share identical hardware and are differentiated solely by software settings – a design choice that simplifies servicing but means neither is strictly optimised for its rated output. The larger three models (7kW, 10kW, and 12kW) are independently engineered for their respective output bands.
| Model | Output | Dimensions (H×W×D) | Weight | Phase |
|---|---|---|---|---|
| aroTHERM Plus 3.5kW | 3.5kW | 862×1,050×427mm | 99kg | Single |
| aroTHERM Plus 5kW | 5kW | 862×1,050×427mm | 99kg | Single |
| aroTHERM Plus 7kW | 7kW | 862×1,200×427mm | 115kg | Single |
| aroTHERM Plus 10kW | 10kW | 862×1,200×427mm | 120kg | Single |
| aroTHERM Plus 12kW | 12kW | 1,067×1,340×520mm | 150kg | Single or Three |
Pricing
Supply-only prices range from £3,990 to £6,770 (trade). Fully installed costs run £9,000-£20,000 before the £7,500 BUS grant, leaving a net cost of £1,500-£12,500 depending on property size.
Vaillant does not publish retail prices directly; the figures below reflect trade pricing supplied through authorised MasterTEC installers and distributor lists verified in February 2026. The aroTHERM Plus requires the sensoCOMFORT controller (sold separately) and is also compatible with the uniTOWER integrated cylinder package for simplified installations.
Supply-Only Prices (Trade, Feb 2026)
| Component | Price (trade) | Notes |
|---|---|---|
| aroTHERM Plus 3.5kW outdoor unit | £3,990 | Includes refrigerant pre-charge |
| aroTHERM Plus 5kW outdoor unit | £4,250 | Same hardware as 3.5kW |
| aroTHERM Plus 7kW outdoor unit | £4,750 | Most popular residential model |
| aroTHERM Plus 10kW outdoor unit | £5,600 | Suitable for larger 4-bed homes |
| aroTHERM Plus 12kW outdoor unit | £6,770 | Available single or three-phase |
| sensoCOMFORT controller | £350-£450 | Required for weather compensation |
| hydraulic module | £900-£1,200 | Required for most installations |
| uniTOWER (190L cylinder package) | £2,800-£3,200 | All-in-one indoor unit option |
Installed Costs by Property Type
| Property Type | Typical Model | Installed Cost | After £7,500 BUS Grant |
|---|---|---|---|
| 2-bed terrace / flat | 3.5kW or 5kW | £9,000-£12,000 | £1,500-£4,500 |
| 3-bed semi-detached | 7kW | £11,000-£14,000 | £3,500-£6,500 |
| 3-bed detached | 7kW or 10kW | £12,000-£16,000 | £4,500-£8,500 |
| 4-bed detached | 10kW or 12kW | £14,000-£20,000 | £6,500-£12,500 |
Note on BUS grant eligibility: The Boiler Upgrade Scheme grant of £7,500 is available for air-to-water heat pumps installed in England and Wales until April 2028, provided the property has an EPC rating of D or above (or a valid exemption) and the system is installed by an MCS-certified contractor. VAT is currently charged at 0% on heat pump installations until March 2027, further reducing the net cost.
The aroTHERM Plus sits at the premium end of the ASHP market. After the BUS grant, a typical 3-bed semi installation costs £3,500-£6,500 – broadly comparable to a premium boiler replacement but with significantly better long-term efficiency and future-proofing. Budget an additional £1,000-£3,000 if radiator upgrades are needed.
Which aroTHERM Plus Size is Right for Your Home?
If you’re searching for "Vaillant aroTHERM Plus 7kW review" or "12kW price", the answer depends as much on your property’s heat loss as on the headline kW number. The summary below pulls together unit cost, peak SCOP, and indicative installed cost (before the £7,500 BUS grant) for each output. Sizing is best confirmed by a Vaillant MasterTEC installer’s heat-loss survey, but this gives a defensible starting point.
| Output | Best for | Unit (trade) | Typical installed | Net after £7,500 BUS | Peak SCOP |
|---|---|---|---|---|---|
| 3.5kW | Well-insulated 1-2 bed flats / very small terraces | £3,990 | £9,000-£11,000 | £1,500-£3,500 | Below peak (shared hardware) |
| 5kW | Small terraces, 2-bed semis (same hardware as 3.5kW, software-limited) | £4,250 | £9,500-£11,500 | £2,000-£4,000 | Below peak (shared hardware) |
| 7kW | 3-bed semis — the most-specified size | £4,750 | £11,000-£13,500 | £3,500-£6,000 | 5.09 (MCS) |
| 10kW | 4-bed detached / less-insulated 3-beds | £5,600 | £13,500-£16,500 | £6,000-£9,000 | 5.09 (MCS) |
| 12kW | Large detached / period properties / where single or three-phase is needed | £6,770 | £15,500-£20,000 | £8,000-£12,500 | 5.03 (range avg) |
Two practical points: the 3.5kW and 5kW are the same physical unit at different software settings, so the 7kW is the first model that’s independently engineered for its rated output. Peak SCOP figures cluster on the 7kW and 10kW units (both 5.09 MCS-certified), which is why those are the two most-specified sizes for retrofit installs.
Key Features
The aroTHERM Plus uses R290 natural refrigerant (GWP 3), delivers 75°C flow temperatures for retrofit without radiator upgrades, and carries Quiet Mark certification on four of five models.
R290 Natural Refrigerant
The single biggest differentiator of the aroTHERM Plus is its use of R290 (propane) refrigerant. With a Global Warming Potential of just 3, R290 is 225 times less damaging to the climate than the R32 refrigerant used in most competing heat pumps (GWP 675) and more than 4,000 times less harmful than the legacy R410A (GWP 2,088). As F-gas phase-down regulations tighten across Europe, systems using natural refrigerants like R290 face no future retrofit requirements or refrigerant availability risks. For buyers who want a system that remains compliant and serviceable for the full 20-year lifespan, this matters enormously.
R290 does require specialist handling due to its mild flammability (A3 classification). All aroTHERM Plus installations must be carried out by Vaillant’s MasterTEC-trained installers who hold the necessary F-gas and A3 refrigerant qualifications. This slightly narrows the installer pool compared to R32 systems, but Vaillant’s MasterTEC network covers the vast majority of the UK.
75°C Flow Temperature for Retrofit
Most heat pumps operate most efficiently at low flow temperatures (35-45°C), which suits underfloor heating or well-oversized radiators. Standard radiators in older UK homes were typically designed for 70-80°C flow temperatures from a gas boiler. The aroTHERM Plus can deliver up to 75°C, meaning it can drive existing standard radiators without replacement in the majority of retrofit scenarios. This is the feature that most frequently tips installers and homeowners toward Vaillant over competitors limited to 60-65°C.
In practice, operating at 75°C significantly reduces the SCOP compared to running at 35°C. The system is not intended to run at maximum flow temperature continuously – rather, it provides a safety margin that makes the aroTHERM Plus viable in homes where radiator replacement is cost-prohibitive. A competent installer will use heat loss calculations to determine the lowest feasible flow temperature for each property.
Quiet Mark Certification
Four of the five aroTHERM Plus models (3.5kW through 10kW) hold Quiet Mark certification, with sound power levels ranging from 48 to 55 dB(A). The 12kW model is rated at 58 dB(A) and does not carry the certification. For context, 50 dB(A) is roughly equivalent to a quiet conversation at 3 metres; 58 dB(A) is closer to a typical office environment. Planning authorities increasingly consider noise when approving heat pump installations in back gardens, and Quiet Mark certification provides documented evidence that the system meets acceptable thresholds.
sensoCOMFORT Weather Compensation
Weather compensation is arguably the most important operational feature of any heat pump. The sensoCOMFORT controller adjusts the system’s target flow temperature automatically based on outdoor ambient temperature – reducing the flow temperature (and energy consumption) as the weather warms. A well-configured weather compensation curve can improve real-world SCOP by 15-20% compared to a fixed-setpoint installation. The sensoCOMFORT also manages hot water scheduling, legionella cycle frequency, and integrates with the myVaillant app via the optional internet gateway.
myVaillant App and Internet Gateway
The myVaillant app (iOS and Android) provides remote temperature control, scheduling, energy monitoring, and system diagnostics. Users can view live system data, set hot water boost modes, and receive service reminders. The app is competent for daily control, though the energy monitoring display has a documented inaccuracy issue: the COP figure shown in the app is calculated using only electrical input to the compressor, not the full system power draw (including controls, pump, and ancillaries). Real-world monitoring from the Heat Geek community consistently shows the app reporting COP of around 2.0 when actual measured values are closer to 3.5. This is a software limitation, not a performance issue, but it can create confusion and unfairly undermine confidence in the system.
The internet gateway (approximately £120-£150) is sold separately and required for app connectivity. It is not included in the base unit price.
uniTOWER Integration
The uniTOWER is a vertical indoor unit combining a 190-litre hot water cylinder, hydraulic module, pump, expansion vessel, and controls into a single floor-standing cabinet. It simplifies installation considerably – Vaillant claims a trained MasterTEC installer can complete a full aroTHERM Plus plus uniTOWER installation in a single day. For properties replacing a combi boiler (which has no existing cylinder), the uniTOWER reduces the complexity and cost of the indirect cylinder installation significantly. It is available in white or anthracite and fits through a standard UK doorway.
Cooling Mode
The aroTHERM Plus hardware supports active cooling through underfloor heating circuits or fan coil units, but this function is locked by default and requires a paid software activation (approximately £500 through a MasterTEC installer). This is a frustration for buyers in warmer climates or south-facing homes who want summer cooling capability as standard. Passive cooling (circulating cooler water through UFH without running the refrigeration cycle) is available without activation but provides limited benefit in UK summers.
MCS Umbrella Partner Scheme
Vaillant operates an MCS Umbrella Partner scheme through its MasterTEC network. Rather than the installing contractor needing individual MCS registration (a barrier for smaller heating engineers), Vaillant’s corporate MCS registration covers MasterTEC-trained installers working under their umbrella. This broadens the eligible installer network and makes BUS grant access more straightforward for homeowners in areas with fewer independently MCS-registered engineers.
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Pros and Cons
The aroTHERM Plus leads the market on environmental credentials and retrofit flexibility, but the app’s COP reporting inaccuracy and cooling being a paid extra are notable frustrations.
Efficiency and Running Costs
Real-world SCOP for well-installed aroTHERM Plus systems runs 3.6-4.0. Annual running costs for a 3-bed semi are approximately £909-£1,125 at Ofgem’s Q1 2026 electricity rate of 27.69p/kWh.
MCS-certified SCOP figures are measured at standardised conditions and represent the best-case scenario. Real-world performance depends heavily on flow temperature, system design, property insulation, and installer setup quality. The table below shows how SCOP degrades as flow temperature increases – underscoring why running the system at the lowest feasible flow temperature is the single most important efficiency decision.
SCOP by Flow Temperature (MCS Certified)
| Model | SCOP at 35°C | SCOP at 45°C | SCOP at 55°C | Max Flow Temp |
|---|---|---|---|---|
| aroTHERM Plus 5kW | 4.64 | 3.43 | 2.78 | 75°C |
| aroTHERM Plus 7kW | 5.03 | 3.72 | 2.95 | 75°C |
| aroTHERM Plus 10kW | 4.90 | 3.65 | 2.90 | 75°C |
| aroTHERM Plus 12kW | 4.72 | 3.48 | 2.80 | 75°C |
Estimated Annual Running Costs
The calculations below use Ofgem’s Q1 2026 electricity price cap rate of 27.69p/kWh and assume average UK space and water heating demand. A real-world SCOP of 3.6 (achievable in a typical retrofit with 45-50°C flow) is used for the base estimate, with a range reflecting best-case (SCOP 4.0, well-optimised system with UFH or low-temperature radiators) and worst-case (SCOP 3.0, older property running at 55°C+) scenarios.
| Property | Annual Heat Demand | Best Case (SCOP 4.0) | Typical (SCOP 3.6) | Worst Case (SCOP 3.0) |
|---|---|---|---|---|
| 2-bed terrace | 8,000 kWh | £554/yr | £615/yr | £738/yr |
| 3-bed semi-detached | 12,000 kWh | £830/yr | £923/yr | £1,108/yr |
| 4-bed detached | 18,000 kWh | £1,245/yr | £1,384/yr | £1,661/yr |
The myVaillant app’s COP display should be ignored as a performance indicator – it consistently underreports real-world efficiency by 40-60%. Homeowners who want accurate monitoring should use a separate electricity meter on the heat pump circuit. The widely documented discrepancy has been acknowledged by Vaillant but not yet corrected via a firmware update as of February 2026.
How It Compares
The aroTHERM Plus leads on environmental credentials and retrofit compatibility, but Samsung’s EHS Mono HT Quiet is measurably quieter, and Mitsubishi’s Ecodan offers superior part-load modulation for new builds with underfloor heating.
The six-brand comparison below covers the UK’s most commonly specified residential heat pumps, using MCS-certified or manufacturer-published SCOP figures at 35°C flow temperature, which is the standard comparison point. Noise figures are sound power level (dB(A)). Supply costs are trade/installer prices verified February 2026.
| Brand & Model | Outputs | Refrigerant | Max Flow Temp | Peak SCOP | Noise (dB) | Warranty | Supply Cost |
|---|---|---|---|---|---|---|---|
| Vaillant aroTHERM Plus PICK | 3.5-12kW | R290 (GWP 3) | 75°C | 5.03 | 48-58 dB | 2-7 yr | £3,990-£6,770 |
| Daikin Altherma 3 HT | 4-16kW | R32 (GWP 675) | 70°C | 5.43 (COP) | 49-62 dB | 5 yr | £4,200-£8,500 |
| Mitsubishi Ecodan | 4.5-14kW | R32 (GWP 675) | 60°C | 4.92 | 45-55 dB | 5 yr | £3,800-£7,200 |
| Samsung EHS Mono HT Quiet | 5-16kW | R32 (GWP 675) | 70°C | 4.80 | 35-46 dB | 5 yr | £3,500-£7,000 |
| Grant Aerona3 R32 | 6-17kW | R32 (GWP 675) | 65°C | 5.41 (13kW) | 52-62 dB | 7 yr | £2,500-£5,000 |
| Nibe F2040 | 6-12kW | R32 (GWP 675) | 65°C | 4.75 | 46-54 dB | 2-5 yr | £5,200-£8,800 |
The Samsung EHS Mono HT Quiet is the standout choice for noise-sensitive installations: its 35-46 dB range undercuts Vaillant by a meaningful margin, and it carries a 70°C flow temperature, making it a strong retrofit contender. Mitsubishi’s Ecodan is the preferred specification for new builds with underfloor heating where maximum flow temperature is less critical, offering superior inverter modulation at very low output levels (down to around 1.5kW on some models). Grant’s Aerona3 is the best-value entry point if budget is the primary concern. The aroTHERM Plus’s decisive advantage is the combination of R290 refrigerant, 75°C flow temperature, and Quiet Mark certification that no single competitor currently matches simultaneously.
aroTHERM Plus vs the Rest of Vaillant’s Heat Pump Range
Vaillant currently sells five heat pump products in the UK. The aroTHERM Plus is the flagship monobloc, but it sits alongside other models targeted at different installation scenarios. If you’ve come here from a search for "aroTHERM Pro", note that Vaillant does not currently market an "aroTHERM Pro" — that name typically appears in installer-network or third-party marketing rather than Vaillant’s official product range. The list below is the actual Vaillant lineup as published on vaillant.co.uk:
- aroTHERM Plus — R290 monobloc, 75°C flow temp, 3.5-12kW. The flagship and the focus of this review — best fit for retrofits and most UK homes.
- aroTHERM Split — refrigerant split system rather than monobloc. Useful where outdoor space is constrained or noise must sit further from the home, but adds an indoor unit and an F-gas-trained installer requirement.
- flexoTHERM — ground- and water-source unit (not air-source). Higher SCOP potential than any ASHP but only viable with land suitable for a borehole or trench loop, plus a substantially higher install cost.
- aroTHERM — the original air-source unit, still listed alongside the Plus. Lower flow temperature and higher-GWP refrigerant than the Plus — specify the Plus over this where retrofit is the goal.
- aroSTOR — an air-source heat pump cylinder for hot water only, not a space-heating product. Often paired with a separate heating system rather than replacing one.
For the vast majority of UK retrofit installations, the aroTHERM Plus remains the right choice within Vaillant’s range. Specify the Split if outdoor noise/space is the binding constraint, or flexoTHERM if you have land for a ground loop and a budget that can absorb £15,000+ extra for the groundworks.
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Warranty
The aroTHERM Plus comes with a 2-year standard warranty, extendable to 7 years at no additional cost when installed by a Vaillant MasterTEC installer who registers the product within 30 days.
Vaillant’s warranty structure for the aroTHERM Plus is straightforward but conditional. The base 2-year parts-and-labour warranty applies to all installations. The extended 7-year warranty – one of the most competitive terms in the market – is available free of charge but requires:
- Installation by a Vaillant MasterTEC-registered engineer
- Product registration on myVaillant Pro within 30 days of installation
- Annual service carried out by a Gas Safe / F-gas registered engineer
- Completion of the MCS Benchmark Commissioning Checklist
The annual service requirement is the most important condition to maintain. Missing a service year voids the extended warranty and reverts to the 2-year base cover. Vaillant’s recommended service cost is £150-£300 per year depending on the engineer and location.
| Brand | Standard Warranty | Extended Warranty | Conditions |
|---|---|---|---|
| Vaillant aroTHERM Plus | 2 years | 7 years (free) | MasterTEC installer + annual service + registration |
| Daikin Altherma 3 | 5 years | Up to 10 years (paid) | Annual service required |
| Mitsubishi Ecodan | 5 years | Up to 7 years (paid) | Registered installer + annual service |
| Samsung EHS | 5 years | N/A | Annual service required |
| Grant Aerona3 | 7 years | N/A | Annual service + online registration |
| Nibe F2040 | 2 years | 5 years (conditions apply) | Nibe-authorised installer |
Vaillant’s 7-year free extended warranty is genuinely competitive – only Grant matches or beats it at the standard level. The key caveat is that the 2-year base warranty is weak relative to Daikin, Mitsubishi, and Samsung’s standard 5-year cover. If you cannot guarantee annual services through a MasterTEC engineer, consider whether the extended warranty is reliably achievable in practice.
Who Should Buy the Vaillant aroTHERM Plus?
The aroTHERM Plus is best suited to UK retrofit projects where existing radiators need higher flow temperatures, and for eco-conscious buyers who prioritise R290’s minimal climate impact over upfront cost.
The aroTHERM Plus is a technically excellent system, but it is not the right choice for every application. If you’re undecided on whether now is the right time, our guide on whether heat pumps are worth it covers the full payback analysis. Understanding where it genuinely leads and where alternatives are more appropriate will save both money and disappointment.
Best For
- Retrofit projects with existing radiators where replacing to low-temperature panels is uneconomical or impractical – the 75°C flow temperature is a decisive advantage
- Eco-conscious homeowners who want the lowest possible environmental impact from their heating system and a future-proof refrigerant choice as F-gas regulations tighten
- Properties with planning sensitivity around noise – Quiet Mark certification on 4 models provides documented evidence for permitted development or pre-application queries
- Buyers prioritising long-term reliability and brand trust – Vaillant’s 4.5/5 Trustpilot score from nearly 23,000 reviews reflects a broadly positive after-sales experience
- Homes replacing an oil or LPG boiler where running cost savings are most pronounced and the higher installed cost is justified by fuel savings alone
- uniTOWER installations where rapid single-day installation minimises disruption – particularly for owner-occupied properties or rental properties between tenancies
Not Ideal For
- New builds with underfloor heating throughout where a Mitsubishi Ecodan’s superior modulation at very low loads provides better part-load efficiency
- Noise-critical locations where the absolute quietest system is required – Samsung’s EHS Mono HT Quiet at 35 dB(A) is measurably quieter than the best Vaillant model
- Budget-constrained buyers where the Grant Aerona3 at a lower supply price offers comparable headline SCOP figures
- Properties where a summer cooling function is a priority – the £500 activation charge for cooling is a hidden cost that tips the calculation toward Samsung or Daikin, which offer cooling as standard
- Buyers who want the longest standard warranty without conditions – Daikin’s 5-year base cover and Grant’s 7-year standard warranty require fewer hoops
Our Verdict
Vaillant aroTHERM Plus review: R290 refrigerant, 75°C flow temp, SCOP up to 5.03. Installed £9,000-£20,000 (£1,500 after BUS grant). Verdict: 8.4/10.
The Vaillant aroTHERM Plus scores 8.5/10 – the UK’s most future-proof ASHP, combining R290 refrigerant, 75°C retrofit capability, and A+++ efficiency. App inaccuracies and premium pricing are the main drawbacks.
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