Vaillant aroTHERM pro

What is the Vaillant aroTHERM pro?

Vaillant's heat pump range has been built around the aroTHERM plus for several years now. The pro sits alongside it as a newer, more affordable option. You get the same core engineering, the same Vaillant reliability and the same sensoCOMFORT controls, but at a lower price and with some features the plus doesn't have today.

The biggest of those features is the Flexible Space Function. Let's talk about that.

The exclusion zone problem, and how the pro solves it

R290 is a natural refrigerant. But it's flammable, which means any R290 heat pump has to meet specific safety rules about where it can be installed.

The main one is the exclusion zone. This is the area around the outdoor unit where you can't have anything that could ignite leaked refrigerant: no plug sockets, no light switches, no openable windows or doors. On a standard installation, that zone extends one metre out from the unit in every direction.

The Vaillant aroTHERM pro has a feature called the Flexible Space Function that changes this. When it's activated, the unit's fan runs at a low speed continuously, even in standby. That constant airflow disperses any potential refrigerant leak before it can build up. As a result, the exclusion zone shrinks dramatically, down to just the area directly below the unit.

In practice that means the pro can go in corners, up against walls, and in spaces where no other R290 unit would pass a safety check. If you've been told a heat pump won't fit in your garden, it's worth asking whether the aroTHERM pro has been considered.

One thing worth knowing: if the Flexible Space Function is active, the outdoor unit needs to stay powered on at all times. That's not normally an issue, but it's something your installer will explain at handover.

What else does the aroTHERM pro offer?

A variable-speed circulation pump

Inside the unit, the circulation pump adjusts its speed based on what the system actually needs rather than running at a constant rate. It's not a dramatic saving on any given day, but it's a real one over the lifetime of the system.

An anthracite finish

Most heat pumps are white. The aroTHERM pro comes in anthracite, a dark grey that looks considerably better against modern homes with dark window frames, grey render, or composite doors. There's also an optional base skirting that hides the feet for a cleaner look at ground level.

The sensoCOMFORT controller

The pro uses the same controller interface as the rest of the Vaillant range. If you've seen a sensoCOMFORT before, you already know how to use this. The unit also has self-calibrating sensors that improve the accuracy of its own performance monitoring over time.

Space and installation flexibility

For properties with very limited ground space, the aroTHERM pro can be wall-mounted. All sizes up to 135 kg are supported. The pro also has a smaller physical footprint than the plus — all three sizes use a single fan, whereas the aroTHERM plus moves to a twin-fan unit at 10 and 12 kW, which means a significantly larger casing. For homeowners already nervous about the visual impact of an outdoor unit, the pro's single-fan design across the full size range is a genuine reassurance.

Technical specifications

Available in 5 kW, 7 kW, and 11 kW. Operates in heating mode from -25°C to +43°C outdoor temperature. Sound power levels of 49 dB(A) for the 5 kW and 7 kW models. A noise reduction mode is available, programmable by time and level.

Is the aroTHERM pro right for your home?

For most UK homes, it's a great option. It's a well-built heat pump from a manufacturer with a long track record, at a price that makes sense for the majority of properties. The Flexible Space Function makes it more installable than anything else currently on the market using R290.

If you have very specific requirements around high flow temperatures or larger properties with unusual heat demands, a Heat Geek installer will be able to tell you whether the plus is worth the extra cost and the right option for you.

The only way to know for certain what's right for your home is a proper heat loss assessment. That's exactly what a Heat Geek Design Consultation covers. Book one and we'll tell you straight.

aroTHERM pro vs aroTHERM plus: side by side

For a deeper comparison, here's how the two units sit against each other across the features that matter most.