Vaillant aroTHERM plus Review:
An Installer’s Guide to the 2026 Range

The right aroTHERM plus size is decided by a room-by-room heat-loss calculation, not by floor area or by the size of the boiler it replaces.

Gas boilers are routinely oversized, because oversizing a boiler costs little. A heat pump is different: an oversized unit cycles on and off inefficiently, while an undersized one struggles on the coldest days. That is why every quote we give follows a full survey.

The table below shows the key figures for Vaillant’s technical data for the 2026 range:

All models are 1,100 mm wide and 450 mm deep, and all run on a standard 230V single-phase supply.

The 10 kW and 12 kW are also available in 400V three-phase versions, with slightly higher CoP figures of 5.39 at A7/W35.

CoP figures are to EN 14511; A7/W35 means 7°C outside air and a 35°C flow temperature.

3.5 kW and 5 kW – smaller and well-insulated homes

At 765 mm tall – about the height of a washing machine – these are the discreet end of the range, suited to smaller houses, bungalows and newer, well-insulated properties with modest heat loss. Both carry the range’s best sound figure at 44 dB(A).

7 kW – the typical three-bedroom retrofit

In our experience this is the size most often specified for a typical three-bedroom semi-detached or detached home of average insulation – though the survey, not the floor plan, makes the final call. It steps up to 965 mm tall and 47 dB(A).

Laboratory efficiency figures are a starting point, not a promise. System design and how you run the heating matter as much as the heat pump itself.

A CoP of 4.92 at A7/W35 means the unit delivers 4.92 kWh of heat for every 1 kWh of electricity, in mild weather with a low flow temperature. Push the flow temperature up to 55°C – closer to how a boiler-era radiator system runs – and the CoP drops to around 2.8-3.2. Over a full year, a well-designed system lands somewhere between those points.

The variables that get you there are correctly sized radiators or underfloor heating, the lowest flow temperature that keeps the house warm, and weather-compensated controls, all of which are design decisions made before installation, which is why the survey matters more than the brochure.

An air source heat pump is a system purchase: the cylinder, controls, and connectivity shape day-to-day running costs as much as the outdoor unit does.

• Hot water. The aroTHERM plus pairs with Vaillant’s uniSTOR pure and plus cylinders, available from 90 to 300 litres in slimline and standard diameters, so there is a fit for most airing cupboards. Vaillant backs the internal stainless-steel tank with a 25-year anti-corrosion guarantee, and pairing the heat pump with a Vaillant cylinder also unlocks the longest heat pump guarantee – see the next section.
• Controls. The sensoCOMFORT control includes weather compensation: an outdoor sensor lets the system adjust flow temperatures automatically as conditions change, which is one of the biggest levers on running cost.
• Connectivity. With the myVAILLANT connect internet gateway, the myVaillant app lets you track energy consumption and set temperatures and schedules from your phone. For aftercare, the myVAILLANT Pro service allows us – with your consent – to monitor the system remotely and read fault codes, which can flag issues early and often saves a diagnostic visit.

Through Infinity Energy Services, the 2026 Vaillant aroTHERM plus carries a guarantee of up to 7 years, depending on the cylinder it is installed with.

As a Vaillant Advance Installer, we can register the following cover on your behalf:

Vaillant’s extended guarantees are conditional on the installation being registered and on routine servicing.

On top of the manufacturer’s cover, our own 2-year insurance-backed workmanship guarantee covers the installation itself: the manufacturer stands behind the equipment, we stand behind the workmanship.

Annual servicing also keeps the system running at its designed efficiency, so it earns its keep either way.

The aroTHERM plus suits most UK homes on paper; whether it suits your particular home is a question the heat-loss survey answers.

The strongest candidates are off-gas-grid homes currently heated by oil or LPG. The running-cost case is best there, and the £9,000 grant really brings the overall cost down.

Homes with reasonable insulation, space for a cylinder, and a workable outdoor position also tend to do very well, and the Flexible Space Function rescues plenty of positions that would previously have failed the siting rules. The points we check before recommending it are radiator sizing, hot water demand, the electrical supply and the noise assessment.

We are technical experts, not a sales company: if the survey says a heat pump is the wrong answer for your property, we will tell you, and explain why.

“We don’t recommend a heat pump until the heat-loss survey tells us it will work. The aroTHERM plus makes that conversation easier. Its 75°C flow temperature means we can often keep the radiators a customer already has, and the new siting rules mean it now fits properties we would have struggled with two years ago.” – Daniel Hanslip, Managing Director, Infinity Energy Services

How much does a Vaillant aroTHERM plus cost?

Most aroTHERM plus installations land between £3,500 and £8,500 after the £7,500 Boiler Upgrade Scheme grant and 0% VAT, which runs until 31 March 2027. Eligible oil and LPG homes get £9,000 instead, bringing the net cost lower. Your exact figure depends on the output size, the cylinder, any radiator upgrades, and the property itself, so we provide a fixed quote after a free survey.

What is the difference between the aroTHERM pro and the aroTHERM plus?

Both use R290 refrigerant and share the same core Vaillant platform and sensoCOMFORT controls. The aroTHERM pro is the newer, more compact single-fan model, available in 5, 7 and 11 kW. The flagship aroTHERM plus covered in this guide offers a wider 3.5-12 kW range, flow temperatures of up to 75°C rather than 70°C, and twin-fan units at 10 and 12 kW for larger properties. We advise on which suits your property at survey.

How loud is the aroTHERM plus?

Sound power on the 2026 range is 44 dB(A) on the 3.5 kW and 5 kW models, 47 dB(A) on the 7 kW and 50 dB(A) on the 10 kW and 12 kW, and Vaillant describes it as the quietest air-to-water heat pump in its portfolio. The level you actually hear at a neighbouring window is lower, and is checked in the MCS noise assessment before installation.

Will it work with my existing radiators?

Often, yes. Flow temperatures of up to 75°C mean the aroTHERM plus can run radiator systems that older heat pumps could not. Whether your radiators are the right size to run efficiently at lower flow temperatures is confirmed in the heat-loss survey; some homes need one or more radiators upsized.

Can I power my Vaillant heat pump with solar panels?

Yes, and the two work well together – though not perfectly. Solar generation peaks in summer while heat demand peaks in winter, so panels will cover much of your hot water in the warmer months and a smaller share of winter heating. Adding battery storage improves things considerably, letting you store daytime generation for evening use. We install solar panels and battery storage alongside heat pumps, so a single survey can cover the whole system.

What grant can I get?

£7,500 through the Boiler Upgrade Scheme for an air-to-water heat pump in England and Wales. From 21 July 2026 until 31 March 2027, eligible off-gas-grid homes heated by oil or LPG receive £9,000 instead. We apply on your behalf and deduct the grant from your quote.

What guarantee does it come with?

Installed by us with a Vaillant cylinder, 7 years. With a third-party cylinder, 5 years; or 7 years with a £200 paid upgrade. Our own 2-year insurance-backed workmanship guarantee covers the installation itself.

How long does installation take?

It varies with the system: the cylinder location, any radiator changes, and the electrical works all affect it. Typically it takes 3-5 days. Our process runs from an initial consultation and desktop survey through system design, an on-site technical survey, installation, commissioning and handover, and we confirm the timescale for your property when we quote.