The Vaillant aroTHERM plus is one of the most capable air source heat pumps (ASHPs) on the UK market. With a Coefficient of Performance (COP) of up to 5.0 at A7/W35 conditions — meaning for every 1 kWh of electricity consumed it delivers up to 5 kWh of heat — it sets a high bar for efficiency. Add MCS certification (a requirement for the government's Boiler Upgrade Scheme grant), an A+++ energy rating, and a range of sizes from 5 kW to 17 kW, and it is easy to see why installers and homeowners alike rate it so highly. Here is what you need to know before committing to one.
Key Specifications at a Glance
The aroTHERM plus is available in six output sizes: 5 kW, 7 kW, 10 kW, 12 kW, 15 kW, and 17 kW. The right size depends on your home's heat loss calculation — a proper room-by-room survey carried out by a qualified installer is essential. Installing an undersized unit in a poorly insulated home will cause it to run flat out in cold weather, reducing efficiency and lifespan.
Noise levels are low for a heat pump of this class: typically 40–45 dB(A) measured at 1 m from the outdoor unit. That is roughly the volume of a quiet conversation, which matters if the unit is close to a bedroom window or a boundary with a neighbour.
The unit carries an ErP (Energy-related Products) rating compliant label and an A+++ seasonal space heating label — the highest available class — confirming its credentials as an efficient low-carbon heating solution.
Smart Controls: eRELAX, myVaillant App and sensoNET
Vaillant includes the eRELAX touchscreen programmer as standard. It handles scheduling and temperature zoning for the unit and, where fitted, a cylinder for domestic hot water. The interface is clean and straightforward, though not as polished as dedicated smart thermostats from brands like Nest or Hive.
For remote access, the myVaillant app (iOS and Android) connects via the optional sensoNET WiFi module. Once fitted, you can adjust schedules, monitor energy usage, and check system status from anywhere. The app has improved considerably in recent software updates and now shows daily and weekly energy consumption broken down by space heating and hot water — genuinely useful data for optimising running costs.
If you already run Home Assistant for heating control, it is worth knowing that third-party integrations for myVaillant exist in the community, though official API access is limited. For tighter home-automation integration, pairing the aroTHERM plus with a compatible smart thermostat via a qualified installer is a more reliable route.
The Boiler Upgrade Scheme: £7,500 Off the Installed Price
Because the aroTHERM plus is MCS certified, it qualifies for the UK government's Boiler Upgrade Scheme (BUS). As of 2024, this provides a £7,500 grant towards the cost of installing an air source heat pump in a property in England or Wales. Your installer applies for the grant on your behalf — you never handle the voucher directly.
Installed prices for the aroTHERM plus typically range from around £8,000 to £14,000 depending on output size, whether a new cylinder is needed, any remedial work on radiators or pipework, and regional labour rates. After the £7,500 BUS grant, the net cost can fall to as little as £500–£6,500 for many installations — though this will vary significantly by property. The Energy Saving Trust's heat pump running cost calculator is a good starting point for estimating ongoing savings versus a gas boiler.
It is worth noting that Scotland has its own equivalent scheme — the Home Energy Scotland Grant and Loan — and Northern Ireland has separate provision. Check the Ofgem BUS pages for the latest grant values, as these are subject to government review.
Compatibility: Radiators, Underfloor Heating and Hot Water
Heat pumps run at lower flow temperatures than gas boilers — typically 35–55°C rather than 70–80°C. This is not a problem for underfloor heating, which is designed for low-temperature operation and works exceptionally well with the aroTHERM plus. If you have a underfloor heating thermostat already installed, your installer can integrate it with the Vaillant controls.
With radiators, you may need to upsize some or all panels to achieve adequate heat output at lower flow temperatures. A heat loss survey will tell you exactly which radiators need replacing. Trying to run a heat pump through undersized radiators is one of the most common reasons for poor real-world performance — do not skip this step.
For domestic hot water, the aroTHERM plus works with a cylinder. Vaillant's own uniSTOR and allSTOR cylinders are designed to integrate neatly, but the unit is compatible with most unvented or vented cylinders of sufficient capacity.
Installation and Warranty
Installation must be carried out by an MCS-accredited installer — this is a requirement for the BUS grant. Vaillant's standard warranty in the UK is typically two years parts and labour, but this is extendable through Vaillant's own extended warranty schemes (terms vary; check with your installer and directly with Vaillant UK for the current offer). Some installers also offer their own workmanship guarantees on top.
The outdoor unit should be sited where there is good airflow, away from obstructions, and on a flat, stable base. Planning permission is generally not required for domestic ASHPs in England under permitted development rights, provided certain conditions around size and proximity to boundaries are met — but it is always worth checking with your local authority before installation.
Running Costs and Real-World Efficiency
The headline COP of 5.0 is achieved under standard laboratory test conditions (A7/W35: 7°C outside air, 35°C water output). In colder UK winters, when ambient temperatures drop and higher flow temperatures may be needed, the real-world Seasonal Coefficient of Performance (SCOP) is lower — typically in the range of 2.5–3.5 for most UK climates, depending on insulation levels and system design. This is still substantially more efficient than a condensing gas boiler, which operates at around 90% efficiency.
Whether a heat pump saves you money compared with gas depends on the electricity-to-gas price ratio, your tariff, and how well your system is designed and commissioned. At current UK energy prices, a well-installed heat pump in a reasonably insulated home can match or beat gas boiler running costs, particularly if you use an off-peak tariff such as Octopus Cosy or Economy 7. For context on whether smart heating upgrades are worthwhile, our guide on whether smart heating is worth it in the UK covers the broader picture.
Verdict
The Vaillant aroTHERM plus earns its reputation as one of the leading ASHPs in the UK market. Its high efficiency, wide size range, low noise output, and MCS certification make it a strong choice for homeowners ready to switch from gas — especially with the £7,500 BUS grant reducing the upfront cost. The smart controls are functional and improving, though home-automation enthusiasts may find the ecosystem less open than they would like.
The key caveat applies to all heat pumps: the technology is only as good as the installation. Proper heat loss calculations, correctly sized radiators or underfloor heating, a quality cylinder, and a skilled MCS installer are non-negotiable. Get those right and the aroTHERM plus is an excellent, low-carbon heating system that should serve your home well for 20 or more years.
Related: best air source heat pump brands UK, heat pump installation costs UK, and heat pump vs gas boiler UK.
