We recently visited Vaillant's UK headquarters and manufacturing site in Belper to get unusually close to the new aroTHERM plus, speak directly with its renewables team and see what has actually changed.

And one of the most interesting improvements isn't its efficiency.

It's where you can put the thing.

The redesigned aroTHERM plus introduces Vaillant's Flexible Space Function (FSF), which can substantially reduce the protective area normally required around an R290 heat pump. That potentially opens up locations close to doors and windows that would previously have been much more difficult to use.

There are improvements elsewhere too.

The latest aroTHERM plus comes in outputs from 3.5kW to 12kW, can produce flow temperatures up to 75°C and uses natural R290 refrigerant. Vaillant quotes efficiency of up to A+++, a maximum COP of 5.39 under specified conditions and seasonal performance figures reaching a SCOP of 5.03.

The smallest model is also rated at just 44dB(A), making this Vaillant's quietest air-to-water heat pump to date.

Lovely collection of numbers.

But the interesting question is whether all that engineering actually fixes the problems homeowners run into when trying to install a heat pump.

Because, as we discovered while making our video, sometimes the problem isn't whether the heat pump can heat the house.

It's whether you're allowed to put it anywhere useful.

Ready to make your home more energy-efficient and cut down on your heating bills? Get a heat pump quote today.

Vaillant aroTHERM plus review: the quick verdict

The Vaillant aroTHERM plus is a premium air source heat pump that is particularly well suited to UK retrofit projects.

Its ability to produce higher flow temperatures gives installers more flexibility when working with existing radiator systems, while its low noise output makes it a sensible option for terraces, semis and homes with nearby neighbours.

The latest aroTHERM plus also addresses one of the less glamorous but surprisingly important problems with R290 heat pumps: siting restrictions.

Its Flexible Space Function actively disperses refrigerant in the unlikely event of a leak, allowing the protective area around the unit to be reduced when the system is appropriately designed and commissioned.

For homeowners with smaller gardens, windows close to the proposed installation position or limited external wall space, that could be just as valuable as another fraction of a point on the efficiency rating.

It is not the cheapest heat pump available, and its standard two-year guarantee looks a little underwhelming until extended-cover conditions are met.

However, its efficiency, controls and established UK support network make it a very strong all-rounder.

Our scores:

In short: it is the German estate car of heat pumps. Sensible, refined and unlikely to start demanding attention halfway up the M6.

Key Vaillant aroTHERM plus specifications

What is the Vaillant aroTHERM plus?

The aroTHERM plus is an air-to-water heat pump.

It absorbs heat from the outside air and uses a compressor to raise its temperature before transferring that energy into your central heating and hot-water system.

Yes, it still works when it is cold outside. There does not need to be a small Mediterranean climate taking place behind your bins.

It is a monobloc system, meaning the refrigerant circuit is sealed inside the outdoor unit. Water pipes then connect the heat pump to the equipment inside your home.

In most installations, that indoor equipment will include:

• A hot-water cylinder

• Heating controls

• Pumps and valves

• Potentially a buffer vessel or volumiser

• Any upgraded radiators required by the system design

This is important if you currently have a combi boiler. A heat pump normally needs stored hot water, so you will need to find room for a cylinder indoors.

What's actually new about the latest aroTHERM plus?

Heat pumps have improved enormously, but one of the industry's problems has been that the installation rules did not always improve at the same speed.

We saw a good example while filming our aroTHERM plus video.

Homeowner Sam had planned his renovation around installing a heat pump. He upgraded insulation, altered his underfloor heating, increased radiator sizes and even changed pipework after surveys of the property.

After roughly nine months and several surveys, the proposed installation was ultimately rejected because of concerns around where the outdoor unit could be positioned and its calculated noise impact on a neighbouring window.

That is quite a lot of effort to end up with precisely no heat pump.

The latest aroTHERM plus has been designed partly around problems like these.

There are two particularly interesting improvements.

1. Flexible Space Function makes positioning easier

The aroTHERM plus still uses R290.

That's propane.

R290 is an excellent refrigerant for heat pumps because of its thermodynamic properties and extremely low climate impact, but it is also flammable.

For that reason, R290 heat pumps normally have manufacturer-defined protective areas around the outdoor unit. Openings such as windows, doors and cellar vents can therefore complicate an otherwise perfectly sensible installation.

Vaillant's new Flexible Space Function, or FSF, attacks that problem directly.

The idea is simple: if refrigerant were ever to escape, the airflow would disperse it rather than allowing propane to accumulate around the unit.

That allows Vaillant to substantially reduce the required protective zone in suitable installations.

It doesn't mean you can literally put the aroTHERM plus anywhere.

Manufacturer requirements, airflow, servicing access, drainage, acoustic calculations and planning rules still apply.

But it potentially removes one of the more awkward limitations of R290 systems, particularly in terraces and smaller properties where there may be a window or door almost everywhere you would sensibly want the heat pump.

2. The new aroTHERM plus is considerably quieter

Noise is another surprisingly common reason otherwise viable heat-pump installations become complicated.

The new-generation aroTHERM plus is Vaillant's quietest air-to-water heat pump so far.

We tested the new Vaillant aroTHERM plus at Vaillant’s UK facility and found it exceptionally quiet at close range.

Vaillant quotes a sound-power level as low as 44dB(A) for the 3.5kW model, although noise output varies by model and operating conditions.

We also heard one operating inside Vaillant's training facility.

Standing next to it, there was remarkably little to hear.

That isn't a scientific acoustic test and homeowners shouldn't interpret it as one. An outdoor installation will behave differently according to load, temperature, positioning and reflective surfaces.

But it does illustrate the disconnect between the enduring image of a heat pump roaring outside the kitchen window and what a modern inverter-driven unit can actually sound like.

🎥 Watch Our Vaillant aroTHERM Plus Heat Pump Case Study

Prefer to see the heat pump rather than read several thousand words about one?

In our case study, we take a closer look at the Vaillant aroTherm, including its construction, controls, key components and how it performed in a UK home:

Vaillant aroTHERM plus sizes

The aroTHERM plus is available in five nominal outputs:

These are only rough examples.

Heat pumps should be selected using a room-by-room heat-loss calculation - not the number of bedrooms, the output of your old boiler or an installer standing in the driveway and squinting thoughtfully at the roof.

A well-insulated four-bedroom home could need less output than a draughty three-bedroom property. Oversizing can also cause cycling, reduce efficiency and shorten component life.

For more detail, read our guide to choosing the right heat pump size.

Reliability: 4.5/5

Vaillant is an established heating manufacturer with a substantial UK installer, service and spare-parts network.

That matters.

A heat pump could be capable of warming Buckingham Palace using the breath of a field mouse, but it is not much use if nobody within 200 miles knows how to service it.

The aroTHERM plus is also a mature product rather than a newly launched experiment.

Vaillant’s product-specific Feefo page displayed almost 200 verified aroTHERM plus reviews when checked in July 2026.

Feedback highlighted by Vaillant includes positive reports about ease of use, quiet operation and maintaining a warm home during sub-zero weather.

As always, reviews should be treated with some perspective. The system’s reliability and comfort will depend heavily on the quality of its design and installation.

A brilliant heat pump installed badly is still a badly installed heat pump.

There is another reason we score Vaillant particularly highly here: serviceability and connectivity.

With myVAILLANT connect, compatible installations can provide installers with remote access to system information through myVAILLANT Pro.

That includes operating data, system status and fault history, potentially allowing an engineer to diagnose a problem before arriving at the property.

Remote monitoring isn't quite the same as the heat pump repairing itself while you watch Netflix, unfortunately.

But for increasingly software-driven heating systems, the ability to see what the appliance is doing without immediately dispatching an engineer is a meaningful advantage.

Performance and efficiency: 5/5

Performance is where the aroTHERM plus earns its premium badge.

Vaillant publishes a maximum SCOP of 5.03 under specific test conditions.

In simple terms, that means the system can produce just over five units of heat for every unit of electricity consumed.

That does not mean every aroTHERM plus will achieve a SCOP of 5.03 in every home.

Real-world efficiency depends on:

• Outdoor temperatures

• Required flow temperature

• Radiator or underfloor-heating design

• Heat loss

• Hot-water use

• Controls and weather compensation

• Installation and commissioning quality

The lower the required flow temperature, the more efficiently a heat pump will generally operate.

A well-designed system running at 35°C to 45°C could produce excellent seasonal results.

A system constantly being asked to fire out 65°C or 70°C water will consume more electricity.

The 75°C flow temperature

One of the aroTHERM plus’s headline features is its ability to reach a flow temperature of up to 75°C.

That makes it more flexible than many conventional low-temperature heat pumps, particularly when retrofitting an older property with existing radiators.

However, 75°C should be viewed as extra capability - not the everyday target.

It is a bit like the top speed on your car. Reassuring to know it is there, but you probably should not use it to collect a prescription.

A professional installer should still design the system to operate at the lowest practical flow temperature. Some radiators may need replacing or upsizing to achieve this.

What does it cost to run?

Using the average July–September 2026 Direct Debit rates quoted in Heatable’s energy price-cap guide:

• Electricity costs approximately 26.11p per kWh.

• Gas costs approximately 7.33p per kWh.

• A heat pump achieving a SCOP of 3.5 produces useful heat for roughly 7.5p per kWh.

• At a SCOP of 4, that falls to approximately 6.5p per kWh.

• A 90%-efficient gas boiler produces useful heat for approximately 8.1p per kWh.

These are simplified comparisons and exclude standing charges. Energy rates also change every three months.

The point is not that an aroTHERM plus is guaranteed to slash every gas-heated home’s bills.

It is that a well-designed system can be highly competitive, while a poorly designed system running at unnecessarily high temperatures can quickly ruin the maths.

Find more examples in our guide to heat pump costs and running expenses.

How quiet is the Vaillant aroTHERM plus?

Very quiet, provided the model is correctly selected and positioned.

Vaillant’s current technical information lists sound power figures from approximately 48dB(A), depending on the model and operating condition.

It also states that sound pressure can fall below 30dB(A) at a distance of three metres under specified conditions.

Several aroTHERM plus outputs have received Quiet Mark certification, although certification and sound levels vary across the range.

In normal-person language, the smaller models should not sound like someone permanently drying their hair behind your fence.

You will hear the fan and compressor when standing close to the outdoor unit, particularly during colder weather or hot-water heating.

Correct placement, anti-vibration measures and the installer’s acoustic assessment remain important.

How quiet is the new Vaillant aroTHERM plus?

Quieter than the model figures previously associated with the aroTHERM plus range.

Vaillant describes the redesigned model as its quietest air-to-water heat pump and quotes sound power from 44dB(A) on the 3.5kW version.

Model size and operating conditions matter, so don't compare that number blindly with a competitor quoting sound pressure from three metres away. They are different measurements.

During our visit to Vaillant's UK facility, we stood directly beside an operating unit and placed our microphone next to it.

It was exceptionally quiet.

That remains an informal demonstration rather than laboratory testing, but it provides useful context for homeowners concerned that installing a heat pump means putting a permanently operating industrial fan outside the window.

You will still hear an aroTHERM plus under certain conditions, particularly at higher loads, during colder weather and when heating hot water.

Good siting and an appropriate acoustic assessment therefore remain important.

Controls and smart features

The aroTHERM plus can be paired with Vaillant’s sensoCOMFORT controller.

This provides weather compensation, adjusting the system’s flow temperature as outdoor conditions change.

It is a small difference with a potentially large effect on efficiency.

With the myVAILLANT connect internet gateway, homeowners can also use the myVAILLANT app to:

• Adjust temperatures

• Set heating and hot-water schedules

• Monitor the system

• Make changes remotely

The gateway and associated controls may not be included in every quotation, so check exactly what your installer has specified.

The digital side is more capable than simply changing the thermostat from your phone.

With myVAILLANT connect installed, the system can feed operating information into Vaillant's connected platform. Installers using myVAILLANT Pro can remotely view system data, status information and fault history and use that information for diagnostics.

That's potentially valuable with heat pumps because poor performance isn't always caused by a failed component.

Sometimes it is a control setting, heating curve or system configuration that needs attention.

Remote visibility gives installers another way of finding those problems without immediately sending somebody to the house.

R290 refrigerant: why it matters

R290 refrigerant and the new Flexible Space Function

The aroTHERM plus uses R290, better known as propane, as its refrigerant.

Before you picture a camping stove cable-tied to the patio, relax.

The refrigerant is contained inside the heat pump's sealed refrigeration circuit and the installation has to comply with Vaillant's siting requirements.

R290 is increasingly important because synthetic refrigerants with much higher global-warming impacts are progressively being phased down.

The trade-off is flammability.

Traditional R290 installations therefore require a protective zone around the unit designed to prevent leaking refrigerant accumulating near openings or ignition sources.

This is where the latest aroTHERM plus gets interesting.

Its new Flexible Space Function can operate the fan at low speed when required to disperse refrigerant should a leak occur.

That means the protective zone can be significantly reduced in appropriate installations, potentially allowing the heat pump to sit closer to windows, doors and other locations that previously created problems.

It's a relatively obscure engineering change that could make a very practical difference to whether a heat pump actually fits around your house.

We visited Vaillant's Belper facility, where the company has invested in UK heat-pump production.

Warranty: 4/5

The Vaillant aroTHERM plus comes with a two-year standard guarantee.

That is adequate, although hardly an excuse to release balloons from the ceiling.

The guarantee can be extended to as much as seven years when the system meets Vaillant’s conditions.

These include installation and registration through an eligible Vaillant partner and, for certain offers, installation with a qualifying Vaillant cylinder. Annual servicing and other terms may also apply.

Always ask your installer to confirm:

• The exact guarantee period included

• Which components are covered

• Whether labour is included

• The servicing requirements

• Who will register the system

• Whether the cylinder and controls have separate cover

“Up to seven years” and “seven years included with this quotation” are not automatically the same thing.

Vaillant aroTHERM plus cost: 4/5

A complete aroTHERM plus installation will typically cost around £9,000 to £15,000 before grants.

The final price depends on far more than the outdoor unit. It can include:

• A suitable hot-water cylinder

• New or upgraded radiators

• Larger pipework

• Electrical work

• Heating controls

• System cleaning

• Groundwork and mounting

• Design, commissioning and certification

A straightforward installation in a reasonably heat-pump-ready home may sit near the lower end.

A larger property requiring several radiator and pipework upgrades can comfortably exceed it.

The aroTHERM plus is not a budget heat pump, but its higher-temperature capability, strong efficiency and UK support network help justify the premium.

Boiler Upgrade Scheme grants

Eligible homeowners in England and Wales can currently receive £7,500 towards an air-to-water heat pump through the Boiler Upgrade Scheme.

Until March 2027, an additional £1,500 is available where both of the following apply:

• The property is heated by oil or LPG.

• The property does not have a mains-gas connection.

That brings the grant to £9,000 for qualifying off-grid properties.

The grant is installer-led, so an MCS-certified installer applies and deducts the approved amount from the price.

You do not receive £9,000 in your bank account to spend on a heat pump, a hot tub and an unnecessarily large ornamental gong.

Hybrid heat-pump systems are not eligible for the BUS.

Installation and space requirements

The smaller aroTHERM plus units measure approximately 1,100mm wide, 765mm high and 450mm deep.

The 10kW and 12kW models are taller, at roughly 1,565mm high, 965mm wide and 450mm deep.

Inside, most homes will need a hot-water cylinder. Vaillant offers matching uniSTOR cylinders, although the precise cylinder size should reflect the household’s hot-water demand.

Installation commonly takes between two and five days, depending on how much work the existing heating system needs.

Expect a proper installation process to include:

• A room-by-room heat-loss calculation.

• Radiator and pipework assessment.

• Outdoor-unit siting and noise calculations.

• Hot-water-cylinder sizing.

• Electrical assessment.

• Installation and system cleaning.

• Commissioning and control setup.

• MCS, warranty and grant paperwork.

If the entire survey consists of somebody asking how many bedrooms you have, it is not a survey. It is small talk.

Is the aroTHERM plus easier to install than older heat pumps?

Potentially, yes, although this needs some qualification.

The video highlighted three barriers that have historically made heat-pump installations unnecessarily difficult:

• R290 safety zones

• Acoustic calculations and neighbour proximity

• Planning restrictions

The product itself now helps considerably with the first two.

FSF gives installers much greater freedom when positioning the heat pump, while the new model's reduced sound output can make acoustic compliance easier.

Planning rules have also become less restrictive in England.

However, don't interpret that as meaning "heat pumps no longer need planning permission".

Most qualifying domestic installations can be completed under permitted-development rights, but restrictions remain depending on the property, number and size of units, listed-building status, location and compliance with the relevant noise standard.

In other words, the direction of travel is much better.

The rulebook has not ceased to exist.

Vaillant aroTHERM plus pros and cons

Pros:

• Excellent maximum SCOP of up to 5.03.

• Flow temperatures up to 75°C provide added retrofit flexibility.

• Broad 3.5kW to 12kW range.

• Quiet Mark certification on eligible models.

• Low-GWP R290 refrigerant.

• Suitable for radiators and underfloor heating.

• Strong UK installer and support network.

• Smart controls and weather compensation available.

• Up to seven years of guarantee cover when the relevant conditions are met.

• Eligible installations can access the Boiler Upgrade Scheme.

Cons:

• More expensive than several entry-level heat pumps.

• Only a two-year standard guarantee.

• The full seven-year guarantee is conditional.

• A hot-water cylinder will usually be required.

• Some homes will still need radiator or pipework upgrades.

• Higher flow temperatures reduce efficiency when used regularly.

• Controls, gateway and cylinder packages can make quotations difficult to compare.

• Larger 10kW and 12kW units need considerably more outdoor space.

Vaillant aroTHERM plus vs the competition

There is no universal best heat pump.

The Vaillant’s special talent is combining premium efficiency with a maximum temperature that gives installers more options in existing homes.

Read our best heat pump brands guide for a wider comparison.

Who is the aroTHERM plus best for?

The Vaillant aroTHERM plus should make your shortlist if:

• You own an existing property with radiators.

• You want a premium heat pump from an established manufacturer.

• Noise is an important consideration.

• You want app-based controls and weather compensation.

• Your home needs more retrofit flexibility than a basic low-temperature model provides.

• You are replacing oil, LPG or direct electric heating.

• You have room for an outdoor unit and hot-water cylinder.

• You value long-term efficiency more than finding the cheapest initial quotation.

Who might want to look elsewhere?

Another model could be a better fit if:

• Your main priority is the lowest possible upfront price.

• You cannot accommodate a hot-water cylinder.

• Outdoor space is extremely restricted.

• Your home needs extensive fabric, pipework and radiator upgrades that you do not want to undertake.

• You want a longer unconditional standard warranty.

• You are expecting boiler-style bursts of heat rather than steady, lower-temperature heating.

Not sure whether your property makes sense? Read our guide: Is my home suitable for a heat pump?

What we learned after seeing the aroTHERM plus in person

Specifications tell only half the story with the latest aroTHERM plus.

The most convincing thing about the new model isn't another decimal point on its efficiency figure.

It's that Vaillant appears to be attacking the boring practical reasons heat-pump projects fail.

Noise: reduced.

R290 siting restrictions: substantially improved through FSF.

Remote diagnostics: increasingly built into the connected system.

Installation flexibility: better.

Appearance: considerably less "commercial refrigeration unit abandoned beside the bins".

There are still limitations.

A heat pump needs competent system design. Some homes need emitter or pipework upgrades. You normally need somewhere for stored hot water. Installation remains considerably more involved than swapping one combination boiler for another.

And no clever fan mode changes the laws of thermodynamics.

But the latest aroTHERM plus feels less like a technology homeowners have to redesign their property around and more like a product being redesigned around actual homes.

That's an important distinction.

Heatable Verdict

The aroTHERM plus was already one of the strongest premium retrofit heat pumps available in Britain.

The new generation is more interesting because Vaillant hasn't merely chased a higher efficiency number.

Its quieter operation and Flexible Space Function address two of the practical issues that have historically prevented heat pumps being installed in otherwise suitable properties.

Combine that with 75°C maximum flow temperatures, R290 refrigerant, outputs from 3.5kW to 12kW, connected diagnostics and Vaillant's established UK service infrastructure, and this remains one of the most complete premium retrofit packages available.

It isn't cheap.

It won't make poor system design irrelevant.

And "more flexible siting" absolutely should not be translated into "put it anywhere you fancy".

But this feels like the direction heat pumps needed to go: less engineering around the house and more engineering inside the heat pump.

Our final score: 4.5 out of 5.

Get the specification and installer right, and the Vaillant aroTHERM plus should keep quietly extracting heat from the British weather while you remain indoors, refusing to make eye contact with February.

Very sensible.

Next Steps For Your Heat Pump Journey:

When planning to install a heat pump for your home, there are several important factors to consider. Make sure to refer to the following guides to help you make informed decisions:

• What is the Boiler Upgrade Scheme?

• Is my home suitable for a heat pump?

• How much do heat pumps cost?

• Best heat pump brands

• What size heat pump do you need?

• Aira heat pump review

• Vaillant SensoComfort review

• Cold climate heat pumps

• Air source vs ground source heat pumps

• Octopus cosy 6 heat pump review

To dive deeper into these topics, head over to our advice section or check out our YouTube channel to learn more.

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• Up to 12-year guarantee on selected heat pumps.

• Fixed price guarantee: No hidden costs.

• Save your quote and decide later.

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