Vaillant is a German heating manufacturer, and its aroTHERM air source heat pumps are designed to replace a gas or oil boiler and heat your home through radiators or underfloor heating. There are two designs to choose from: a monobloc, where the refrigerant stays sealed in the outdoor unit, and a split, where refrigerant pipes link a compact outdoor unit to an indoor unit.
A monobloc heat pump using natural R290 refrigerant, with flow temperatures up to 75°C for more flexibility with existing radiators and hot water. Five sizes from 3.5kW to 12kW, and Quiet Mark certified on most sizes.
Monobloc
A compact outdoor unit linked by refrigerant pipes to a wall-mounted indoor unit. It comes pre-filled for pipe runs up to 15 metres, is Quiet Mark certified and is available from 3.5kW to 12kW.
Split
Both models suit typical UK homes. The main differences are the refrigerant, how hot they can run and how the outdoor unit connects to your home.
| aroTHERM plus | aroTHERM split | |
|---|---|---|
| Type | Monobloc | Split |
| Outputs | 3.5, 5, 7, 10 and 12kW | 3.5, 5, 7, 10 and 12kW |
| Refrigerant | R290 (natural) | R410A |
| Max flow temperature | Up to 75°C | 55°C for heating |
| Noise | Quiet Mark (all sizes except 10kW) | Quiet Mark certified |
| Warranty | 2 years standard, up to 7 years with a qualifying installer and Vaillant cylinder | 2 years standard, up to 7 years when registered with a Vaillant cylinder |
| Best for | Most homes with radiators, especially where higher flow temperatures help | Homes with little outdoor space, or where the unit needs to sit away from the house |
Our comparison guides put each model side by side in plain English, so you can see the differences before you speak to an installer.
The aroTHERM plus ticks the boxes most people look for. It uses natural R290 refrigerant, reaches flow temperatures up to 75°C, carries an A+++ energy rating, works in outdoor temperatures down to minus 25°C and is Quiet Mark certified on most sizes. How well any heat pump performs still depends on the design and installation, so the installer matters as much as the brand.
A Vaillant heat pump is priced as part of a full installation, so there's no single figure. The Energy Saving Trust puts the typical cost of installing an air source heat pump at around £14,000. Your price depends on the size of the unit, your home, whether radiators need upgrading and the cylinder and controls you choose. In England and Wales, the £7,500 Boiler Upgrade Scheme grant comes off the bill.
It's one of the quieter options. The 3.5kW, 5kW, 7kW and 12kW aroTHERM plus models are Quiet Mark certified, an independent award for quieter products. Close to the unit you'll hear a gentle fan and compressor hum, and much less from inside. A good installer will also choose the position carefully so noise isn't an issue for you or your neighbours.
Vaillant gives a 2-year guarantee as standard, and this can be extended up to 7 years. The longer cover depends on your installer: it's available through Vaillant's Platinum and Renewable Partner installers who register the heat pump with a Vaillant cylinder. The heat pump must be registered within 30 days of installation, so ask your installer which level of cover you'll get.
For most homes the aroTHERM plus is the natural choice, as everything sits in one outdoor unit, it runs on R290 and it reaches 75°C. The aroTHERM split suits homes where outdoor space is tight or the unit needs to sit further from the house, up to 15 metres on its pre-filled refrigerant. The right size comes from a room-by-room heat loss survey.
Yes. Vaillant says the aroTHERM plus is eligible for the Boiler Upgrade Scheme, as long as you meet the scheme rules. In England and Wales, the Boiler Upgrade Scheme gives £7,500 towards an air source heat pump, or £9,000 if your off-gas-grid home is replacing oil or LPG, thanks to an extra £1,500 available until March 2027. Your installer applies on your behalf. In Scotland, Home Energy Scotland offers grant funding instead.
Often, yes. The aroTHERM plus can reach flow temperatures up to 75°C, which gives it more flexibility with existing radiators than lower-temperature models. Heat pumps run most efficiently at lower temperatures, though, so your installer may suggest swapping a few radiators for larger ones. A proper heat loss survey will show exactly what each room needs.
Vaillant doesn't publish a set lifespan, and how long any heat pump lasts depends on it being sized correctly, installed well and looked after. The firmest guide is the guarantee, which runs up to 7 years with a qualifying installer. Ask your installer about an annual service, as regular checks help catch small problems before they become big ones.
Our recommended installers
These recommended installers in our network fit Vaillant heat pumps. Each one designs the system around your home, from the heat loss survey to the final handover.
Tell us where you live and we’ll point you to our recommended installer for your area, who can survey your home and size the right model for you.
