Home Heat Pump Guide

Vaillant Arotherm Heat Pump Review

Vaillant is a name that millions of UK homeowners already know from their gas boilers. The German manufacturer has been in the heating industry since 1874, and their transition into heat pumps has produced one of the most technically advanced domestic models on the market: the Arotherm Plus. What sets it apart from most competitors is its use of R290 (propane) refrigerant — a natural substance with a global warming potential of just 3, compared to 675 for R32 used by most rivals.

This review examines the Vaillant Arotherm Plus range in detail, covering real-world performance in UK homes, pricing, warranty, and whether it deserves its growing reputation as one of the best heat pumps available in Britain.

The Vaillant Arotherm Plus Range

The Arotherm Plus is Vaillant's flagship air-to-water heat pump for the UK domestic market. It is a monobloc design, meaning all refrigerant components are contained within the outdoor unit. Only insulated water pipes and electrical cables connect it to the indoor system.

Key Specifications

  • Capacity range: 3.5kW, 5kW, 7kW, 10kW, 12kW, and 15kW models
  • Refrigerant: R290 (propane) — GWP of 3
  • SCOP (at 35°C flow): Up to 4.65 (5kW model)
  • SCOP (at 55°C flow): Up to 3.37
  • Max flow temperature: 75°C
  • Noise at 1m: 38 to 48dB (varies by model and output)
  • Operating range: -25°C to +40°C outdoor temperature
  • Weight: 112 to 175kg (varies by model)

R290 Refrigerant: Why It Matters

The Arotherm Plus's most significant differentiator is its use of R290 (propane) as a refrigerant. While most domestic heat pumps in the UK use R32, Vaillant has moved to R290 across the Arotherm Plus range. Here is why this matters:

Environmental Impact

R290 has a global warming potential (GWP) of just 3. R32, used by Daikin, Mitsubishi, and others, has a GWP of 675. The older R410A, still used in some models, has a GWP of 2,088. If you care about the full environmental impact of your heating system — not just the carbon saved from switching away from gas — R290 is the clear winner.

Future-Proofing

EU and UK regulations are progressively tightening restrictions on high-GWP refrigerants. The F-gas Regulation is driving the industry towards natural refrigerants like R290. By choosing an R290 system now, you are ahead of regulatory changes that will eventually affect R32 availability and servicing costs.

Practical Considerations

R290 is mildly flammable (A3 classification), which means the outdoor unit must maintain certain clearance distances from building openings (windows, doors, vents). For most UK installations, this is straightforward — the unit needs to be positioned at least 750mm from any opening into the building, depending on the charge size. This is rarely a problem in practice but needs to be confirmed during the site survey.

The R290 charge in the Arotherm Plus is relatively small (under 1kg in most models), which minimises any safety considerations and means that installation does not require the same level of F-gas certification as systems with larger refrigerant charges.

High Flow Temperature: 75°C Capability

The Arotherm Plus can deliver flow temperatures up to 75°C, which is one of the highest available in any domestic air source heat pump. This is significant for several reasons:

  • Existing radiators: Older homes with standard radiators designed for a gas boiler (typically running at 65 to 75°C) can use the Arotherm Plus without replacing radiators in many cases
  • Solid-wall properties: Stone-built homes and other poorly insulated properties that need higher temperatures to maintain comfort can use the Arotherm Plus effectively
  • Domestic hot water: Higher flow temperatures mean faster hot water cylinder recovery times and the ability to run anti-legionella pasteurisation cycles without an electric immersion heater

However, it is important to understand the efficiency trade-off. At 75°C flow temperature, the COP drops significantly — to around 2.0 to 2.3 in real-world conditions. The system is most efficient at 35 to 45°C, where COP reaches 3.5 to 4.0. The 75°C capability is best thought of as a safety net for peak demand or hot water pasteurisation, rather than the normal operating mode.

Real-World COP Performance

Based on monitored installations in UK homes, the Vaillant Arotherm Plus typically achieves:

  • 3.3 to 4.0 seasonal COP when running at 35 to 40°C flow temperature (well-insulated homes with underfloor heating or large radiators)
  • 2.7 to 3.3 seasonal COP when running at 45 to 55°C (moderately insulated homes, standard radiators)
  • 2.0 to 2.5 seasonal COP when running at 60 to 75°C (poorly insulated homes needing high temperatures)

These figures are among the best in the industry and are consistent with the manufacturer's SCOP ratings. Weather compensation — where the system automatically reduces flow temperature as outdoor temperatures rise — is key to maximising efficiency and should always be enabled.

Indoor Components and Controls

The Arotherm Plus integrates with Vaillant's wider system components:

uniTOWER Plus

Vaillant's uniTOWER Plus is an integrated hydraulic station and hot water cylinder in one unit. Available in 190-litre and 290-litre versions, it contains the circulating pump, expansion vessel, and controls alongside the hot water storage. This reduces the number of separate components and simplifies installation.

sensoCOMFORT Controller

The wall-mounted sensoCOMFORT is a clear, well-designed controller that allows homeowners to set heating schedules, adjust temperatures, and monitor system status. It is one of the better controller interfaces on the market — intuitive enough for most homeowners to use without referring to the manual.

myVAILLANT App

Vaillant's smartphone app provides remote monitoring and control. You can adjust temperatures, change schedules, and view basic energy data from anywhere. The app also allows your installer to monitor the system remotely and diagnose issues, which can mean faster support when problems occur.

Noise Levels

The Arotherm Plus achieves noise levels of 38 to 48dB at one metre, depending on the model size and operating load. The smaller models (3.5kW and 5kW) are particularly quiet at 38 to 40dB — comparable to a quiet library.

The inverter-driven compressor allows the unit to modulate its output rather than cycling on and off, which reduces noise during normal operation. At partial load (which is the majority of operating time), noise levels are lower than the rated figures.

Noise compliance with MCS standards is typically straightforward with the Arotherm Plus, even on smaller properties with close neighbours. The main consideration is the R290-related clearance distances, which may slightly constrain placement options compared to R32 units.

Installation

Vaillant benefits from having one of the largest installer networks in the UK, built up over decades of gas boiler installations. Many existing Vaillant Advance installers have now been trained on the Arotherm Plus range, which means finding a competent, experienced installer is easier than with some other brands.

The monobloc design means the outdoor unit arrives with the refrigerant circuit factory-sealed. Installation involves:

  1. Preparing a level concrete base or wall-mounted bracket for the outdoor unit
  2. Running insulated flow and return water pipes from the outdoor unit into the property
  3. Connecting to the uniTOWER or separate cylinder
  4. Electrical connections (dedicated circuit from the consumer unit)
  5. Commissioning — setting weather compensation curves, flow temperatures, and schedules

Typical installation takes one to two days for a straightforward replacement of a gas boiler.

Warranty

Vaillant offers a 5-year standard manufacturer warranty on the Arotherm Plus. This can be extended to 7 years if the system is installed by a Vaillant Advance installer and registered within 30 days of installation.

The warranty covers all major components including the compressor, heat exchangers, and electronic controls. As with all heat pump warranties, regular annual servicing is a condition of the warranty, and the system must be installed by a qualified professional.

Pricing

Vaillant Arotherm Plus unit prices (before installation) typically range from:

  • 3.5 to 5kW models: £4,000 to £5,000
  • 7 to 10kW models: £5,000 to £6,000
  • 12 to 15kW models: £6,000 to £7,000

Total installed costs including the uniTOWER, controls, pipework, and commissioning typically range from £9,000 to £15,000. After the Boiler Upgrade Scheme grant of up to £7,500, out-of-pocket costs are typically £2,500 to £8,000.

Vaillant is positioned at the premium end of the market. You will typically pay £500 to £1,500 more for a Vaillant system than for a comparable Samsung or Mitsubishi installation. The premium reflects the R290 technology, high flow temperature capability, and the Vaillant brand.

Vaillant vs Competitors

Vaillant vs Daikin

Daikin Altherma 3 achieves similar SCOP figures and lower noise levels on some models. Vaillant wins on refrigerant (R290 vs R32), maximum flow temperature (75°C vs 55/70°C), and arguably on controller quality. Daikin has a longer track record in heat pumps specifically.

Vaillant vs Mitsubishi Ecodan

Mitsubishi Ecodan has the largest installed base in the UK and arguably the best long-term reliability data. Vaillant offers higher flow temperatures, R290 refrigerant, and higher SCOP. Mitsubishi is typically cheaper. Both have excellent UK installer networks.

Vaillant vs Bosch Compress 7400i

Bosch also uses R290 and offers similar high flow temperatures. The Vaillant Arotherm Plus has slightly higher SCOP ratings and a more established heat pump installer network. Both are strong choices for homeowners prioritising environmental credentials.

Pros and Cons Summary

Pros

  • R290 refrigerant — lowest environmental impact, most future-proof
  • 75°C maximum flow temperature — works with existing radiators in older homes
  • Excellent SCOP figures — up to 4.65 at 35°C
  • Massive UK installer network from boiler heritage
  • High-quality sensoCOMFORT controller and myVAILLANT app
  • Monobloc design simplifies installation
  • Wide capacity range from 3.5kW to 15kW
  • Strong brand recognition and after-sales support in the UK

Cons

  • Premium pricing — typically the most expensive mainstream option
  • R290 clearance distances may restrict placement in some tight spaces
  • The outdoor unit is heavier than some R32 alternatives (112 to 175kg)
  • 7-year maximum extended warranty — shorter than Daikin's 10-year option
  • Less heat pump-specific track record than Daikin or Mitsubishi (Vaillant's heritage is in boilers)

Who Is the Vaillant Arotherm Plus Best Suited For?

  • Homeowners who prioritise environmental credentials and want the lowest-GWP refrigerant
  • Older properties that need higher flow temperatures without replacing all radiators
  • Homeowners switching from a Vaillant gas boiler — the existing installer relationship and familiarity with the brand can smooth the transition
  • Anyone who values a premium product with strong UK support and excellent build quality

Frequently Asked Questions

Is the Vaillant Arotherm Plus a good heat pump?

Yes. It is one of the best domestic air source heat pumps available in the UK. The combination of R290 refrigerant, high flow temperatures, excellent SCOP, and Vaillant's UK support network makes it a strong choice for most UK homes.

How much does a Vaillant heat pump cost installed?

Total installed costs typically range from £9,000 to £15,000 before the BUS grant. After the grant, homeowners typically pay £2,500 to £8,000.

Is the R290 refrigerant safe?

Yes. R290 (propane) is mildly flammable but the small quantities used (under 1kg in most models) and the outdoor installation mean the risk is negligible. The system is designed with safety features to prevent leaks, and the refrigerant is contained entirely within the outdoor unit.

Can the Vaillant Arotherm work with my existing radiators?

In many cases, yes. The 75°C maximum flow temperature means it can deliver enough heat through existing radiators in most homes. However, running at lower flow temperatures (35 to 45°C) is significantly more efficient. Your installer should calculate whether existing radiators are large enough at lower temperatures, or whether a compromise flow temperature achieves the best balance of comfort and efficiency.

What is the warranty on a Vaillant Arotherm Plus?

5 years standard, extendable to 7 years through a Vaillant Advance installer. Regular annual servicing is required to maintain the warranty.

How does Vaillant compare to other brands?

Vaillant sits at the premium end of the market. It matches or beats most competitors on efficiency and exceeds all on environmental credentials (R290 refrigerant). The main trade-off is price — you will typically pay more than for a Samsung or Mitsubishi equivalent. See our full brand comparison guide for details.