Vaillant aroTHERM plus heat pump

The Vaillant aroTHERM plus is an air source heat pump sold in five outputs: 3.5kW, 5kW, 7kW, 10kW and 12kW¹. It is an air-to-water monobloc, meaning the outdoor unit heats water that circulates to radiators, underfloor circuits and a hot water cylinder, and the refrigerant circuit is sealed at the factory rather than run as pipework into the house. Vaillant describes it as ideal for retrofit and new building, and pairs it with a Vaillant hot water cylinder and indoor unit¹.

The headline numbers are an ErP rating of up to A+++, a sound power figure as low as 54 dB(A) at three metres, and a standard guarantee of 2 years that can be extended to 7 years when the unit is installed and registered with a Vaillant cylinder by a Platinum or Renewable Partner installer¹. It runs on R290, a natural refrigerant with a global warming potential of 3³.

For a household, the appeal is straightforward: the unit draws heat from outside air rather than burning gas on site, so the fuel dependence shifts from a gas supplier to electricity. What remains is a dependence on the grid, on a competent installer for the guarantee terms, and on Vaillant for parts, servicing and the app that runs the controls.

What the aroTHERM plus is: an air-to-water monobloc

The aroTHERM plus is an air source heat pump that takes heat from the air outside and delivers it as hot water for space heating and domestic hot water⁴. It is a monobloc design, so the refrigeration circuit is completed and charged in the factory and only water pipework and electrical connections cross the boundary of the house. That matters for installation: there is no need for an F-Gas qualified engineer to make refrigerant joints on site, and the outdoor unit can be sited with more flexibility.

Vaillant positions the unit as part of a system rather than a standalone box. The aroTHERM plus paired with a Vaillant hot water cylinder and indoor unit is described as ideal for a wide range of properties, and the maker states it can provide up to 25% more usable hot water with a 75 degrees C flow temperature¹. That higher flow temperature matters in retrofit, where existing radiators may be sized for a boiler rather than a heat pump.

The applications listed are domestic hot water and heating². There is a base cover accessory available at the point of installation to tidy the pipework entry². The wider Vaillant range includes the aroTHERM, a four-model line covering 5, 8, 11 and 15kW heating output, and the aroTHERM split, which separates the outdoor and indoor sections⁴. The aroTHERM pro is a separate line available in 5, 7 and 11kW outputs⁶.

Range and outputs: 3.5 to 12kW, and which suits which home

Five outputs are available: 3.5kW, 5kW, 7kW, 10kW and 12kW¹. The same list appears in Vaillant's technical documentation, which records 3.5, 5, 7, 10 and 12kW models⁷, and in independent listings from Quiet Mark, which describes the range as available in 3.5kW, 5kW, 7kW, 10kW and 12kW outputs³. Ofgem's approved innovation measures list also records the Vaillant aroTHERM Plus ASHP at 3.5kW, 5kW, 7kW, 10kW and 12kW⁹.

The spread is wide enough to cover most UK homes. The smallest unit suits a well-insulated flat or a small house with modest heat loss; the largest suits a larger detached property or one with poorer fabric. Output is not a matter of picking the biggest number: a heat pump that is oversized cycles on and off, which reduces efficiency and increases wear, while one that is undersized struggles to hold temperature in a cold snap. The correct figure comes from a room-by-room heat loss calculation, not from floor area alone.

The 3.5kW and 5kW models carry an energy efficiency class of A++ at 35 degrees C on the maker's datasheet¹¹. The 10kW and 12kW units are listed at a sound power of 51 dB(A) at A7/W35, and the 7kW at 49 dB(A)¹¹. Sizing decisions belong with a competent installer working from measured heat loss, and the wider subject is covered under heat pump sizing.

Efficiency: SCOP up to 5.03 and A+++ ratings

Vaillant states the aroTHERM plus has an energy efficiency class of A+++¹, and describes an ErP of up to A+++ that ensures performance for both underfloor heating and radiators². Quiet Mark's independent listing records a highest ErP rating of A+++ and a SCOP of up to 4.88⁸. The documents give different seasonal figures, and the difference reflects the model, the flow temperature and the test basis rather than a dispute about the appliance.

The gap between a headline SCOP and what a household sees is the important part. One customer review installation published by Vaillant reports a SCOP of 4.2 from January to July, with the house kept at the heating setpoint through the winter¹. That is a real installation over a real heating season, and it sits below the quoted maximum. Seasonal performance depends on flow temperature, emitter sizing, insulation, controls and how the system is commissioned.

The practical lever is flow temperature. A heat pump gains most when it runs at the lowest temperature that still heats the house, which is why underfloor circuits and generously sized radiators perform better than undersized ones. The subject is set out in more detail under heat pump efficiency and flow temperature.

Noise: as low as 54 dB(A), with Quiet Mark on all but the 10kW model

Vaillant states the aroTHERM plus has sound power as low as 54 dB(A) at a three metre distance, and that the range has been awarded Quiet Mark, with the 10kW model excluded from that claim¹. A separate Vaillant page gives a particularly low noise level of only 44 dB(A), based on the 3.5kW model². The two figures are not the same measurement: one is sound power at three metres across the range, the other is tied specifically to the smallest unit.

The maker's datasheet gives model-level sound power figures at A7/W35: 48 dB(A) for the 3.5kW model, 49 dB(A) for the 7kW, and 51 dB(A) for the 10kW and 12kW units¹¹. A spec sheet also records an acoustic pressure level of less than 30 dB(A) from three metres away, which it presents as an aid to planning and siting⁷. Independent case study material repeats the 54 dB sound power figure¹².

Noise is the most common planning concern for air source heat pumps, and the assessment method is set out under MCS 020 and heat pump noise. Siting, clearances and the position of neighbouring windows usually matter more than the decibel figure on the datasheet.

R290 refrigerant and why its global warming potential matters

The aroTHERM plus operates using R290 refrigerant¹³. R290 is propane, a natural refrigerant, and Quiet Mark's listing records that the aroTHERM plus uses a natural refrigerant with an exceptionally low global warming potential of just 3³. For comparison, the same independent listing source records an LG Therma V R290 Monobloc at a GWP of 3¹⁴, so the figure is a property of the refrigerant rather than a claim unique to one maker.

Global warming potential measures how much a gas warms the atmosphere relative to carbon dioxide over a set period. A low figure matters because refrigerant can escape during manufacture, servicing or disposal, and because the F-Gas rules increasingly push the market towards lower-GWP options. A refrigerant with a GWP of 3 carries a far smaller penalty if it leaks than the fluorinated gases it replaces.

R290 is also mildly flammable, which shapes how the unit is installed and serviced rather than whether it can be used domestically. The wider comparison between refrigerant types is covered under heat pump refrigerants and R290 vs R32.

Controls and smart features: sensoCOMFORT, sensoHOME and the myVAILLANT app

Vaillant's control ecosystem for the aroTHERM range centres on the sensoCOMFORT heating control, which allows management of all heating appliances through the touchscreen unit or remotely, paired with the myVAILLANT connect internet gateway and the myVaillant app⁵. The sensoCOMFORT, sensoHOME and sensoROOM controls form the current line.

This is where the clearest dependence in the system sits. Local control at the unit and at a wired programmer continues without an internet connection, but scheduling from away, energy monitoring and remote diagnostics depend on a home broadband connection, on Vaillant's servers and on a manufacturer's app. A household that wants to run the system without that chain can do so, but loses the remote functions.

The controls subject is developed under heat pump controls, including weather compensation, which adjusts flow temperature to outdoor conditions and is one of the largest single influences on real-world running cost.

Cooling, PV compatibility and SG-ready flexibility

Vaillant states that its heat pumps easily integrate with PV systems, whether the solar was installed before the heat pump or as part of a wider renovation², and the maker's datasheet records that the aroTHERM plus can also be combined with photovoltaic systems¹¹. That pairing works because a heat pump runs on electricity, so self-generated power offsets imported units rather than being sold back at a lower rate.

The aroTHERM plus is also compatible with hybrid arrangements. Quiet Mark's listing for the Vaillant ecoTEC sustain combi boiler range records that it is compatible with aroTHERM air-to-water heat pump hybrid system¹⁵, so a household can keep a gas boiler alongside a heat pump rather than removing it. That changes the dependence profile: a hybrid keeps the gas connection and the gas supplier, and adds a heat pump for the milder part of the year.

Cooling is a further option on air-to-water systems, and the subject is covered under heat pump cooling. The comparison between a hybrid and a full heat pump is set out under hybrid heat pumps and hybrid vs full heat pump cost.

Warranty: 2 years standard, extendable to 7 years

The aroTHERM plus comes with a 2-year standard guarantee, extendable up to 7 years when installed with a Vaillant cylinder fitted by a myREWARDS installer². The same structure applies across the range: the aroTHERM split carries a 2-year standard guarantee extendable up to 7 years⁵, and the aroTHERM pro carries a 2-year guarantee as standard after installation, with Cover and Care packages extending it up to 10 years⁶.

The 7-year term is conditional, and the conditions are specific. Availability is limited to Platinum and Renewable Partner installers who also register the appliance with a Vaillant cylinder, and upgrades may incur charges if the installer is a lower tier or if a cylinder has not been installed¹. The same wording appears on the aroTHERM plus page: eligibility applies when installed and registered with a Vaillant cylinder, and if an eligible cylinder is not installed, additional upgrade costs may apply².

Registration runs through the installer or through Vaillant, using the benchmark Commissioning record from the back of the product manual¹⁶. Servicing terms also appear in scheme documentation: Ofgem's approved innovation measures record a 12-year warranty at no cost to the end-user for the Vaillant aroTHERM Plus ASHP, with servicing each year for 11 years beginning 12 months after the installation date⁹. That is a scheme-specific arrangement rather than the standard retail term, and the two should not be conflated. The relationship between servicing and cover is covered under heat pump servicing and warranty.

Cost, the Boiler Upgrade Scheme and buying in the UK

There is no published Vaillant list price for a supplied and fitted aroTHERM plus. Prices are installer-quoted after a survey, and the figure depends on the output chosen, whether radiators or pipework need upgrading, and the siting and electrical work involved.

The grant position is where the documents diverge, and the divergence is worth stating plainly. Vaillant states the aroTHERM plus is eligible for the Boiler Upgrade Scheme grant in England and Wales¹, and elsewhere states the aroTHERM is covered by the scheme with a £7,500 grant towards the cost and installation of a heat pump⁴. The Energy Saving Trust describes the scheme as a grant for people in England or Wales to get up to £7,500 off the cost of installing a heat pump¹⁷. Ofgem's scheme rules state £9,000 off the cost and installation of air-to-water or ground source heat pumps in eligible off-gas grid properties, available until 31 March 2027¹⁸, and government guidance states that until March 2027 an additional £1,500 is available towards an air source or ground source heat pump¹⁹. A separate official notice records a £9,000 figure²⁰.

The scheme is administered by Ofgem¹⁸, and grants assist with installation costs²². It applies in England and Wales, so households in Scotland and Northern Ireland fall outside it and rely on different support. The wider picture across the four nations is covered under heat pump grants and heat pump cost.

On buying, Vaillant directs buyers to choose a retailer to explore purchasing options³, and the extended guarantee terms are tied to accredited installers¹. Most households buy the unit as part of a supplied and fitted installation rather than as a standalone purchase.

Vaillant as a maker: 150 years, family-owned and UK support

Vaillant Group UK operates more than 250 service engineers across the UK¹³. The company's sustainability report records the Belper manufacturing plant receiving the RoSPA President's Award in 2025 after ten consecutive RoSPA Gold Awards, a battery-powered shunting vehicle trial with Kinaxia and Volvo, the launch of the Growing Communities platform, and the establishment of a Training and Learning Council¹³. In 2025 the company also helped restore heating and hot water for 87 residents in Derbyshire through work with YMCA Derbyshire¹³.

Independent product material describes Vaillant as combining proven German engineering with award winning UK manufacturing¹⁵. The ecoTEC plus system boiler range is described as engineered in Germany and manufactured in the UK²³, which is the pattern across the group's UK operations.

For repairs, Vaillant's heat pump line for units in guarantee is 0330 100 3540, option 1, and the call centre is open 7 days a week, 364 days of the year²⁴. Out of guarantee, the company offers an annual maintenance and support plan or a one-off repair, booked through the myVaillant Web portal²⁴. Diagnosis stays tied to the manufacturer, since the fault code list and the in-guarantee repair route both run through Vaillant.

The dependence this creates is worth naming. A household that installs an aroTHERM plus keeps a relationship with Vaillant for parts, servicing and the app, and with an accredited installer for the guarantee terms. The fuel dependence shifts from gas to electricity, which means the grid and an electricity supplier rather than a gas supplier. The wider subject is covered under heat pumps and energy independence and Vaillant heat pumps.