Vaillant aroTHERM Plus Review
| Spec | Detail |
|---|---|
| Refrigerant | R290 (propane) |
| COP (A7/W35) | Up to 5.1 |
| Noise level | 54 dB(A) at 3m |
| Capacities | 3.5–15kW |
| Installed price | £10,000–£14,000 |
| Warranty | 7 years (10 with registration) |
The Vaillant Arotherm Plus is the one to beat in the UK right now. If you want the best-performing air source heat pump on the market and you can stretch the budget, this is it. Full stop.
Why R290 matters
Most heat pumps still run on R32 or R410A refrigerants. Both are synthetic HFCs with high global warming potential, and both are being progressively phased down under F-gas regulations. The Arotherm Plus uses R290 — propane — a natural refrigerant with a GWP of just 3. Compared to R410A's GWP of 2,088, that's not a marginal improvement. It's a different league entirely.
This isn't just an environmental talking point. It's a genuine future-proofing argument. When synthetic refrigerants become harder and more expensive to service in the years ahead, R290 systems won't have that problem. You're buying ahead of the curve.
The performance numbers
A COP of 5.1 at A7/W35 means that for every 1kW of electricity you put in, you get 5.1kW of heat out. That's exceptional. In the real world, installed COPs will be lower — they always are — but the ceiling is high, and well-installed Arotherm Plus systems consistently outperform the competition in independently monitored datasets.
At 54 dB(A) at 3 metres, it's also one of the quietest units on the market. That matters if your outdoor unit is near a neighbour's boundary, a bedroom window, or your own garden where you actually want to sit in summer.
The capacity range works for most homes
The 3.5–15kW range covers everything from a well-insulated modern flat to a large detached house with a higher heat loss. The 3.5kW unit in particular is useful for smaller, better-insulated homes where a lot of heat pumps are oversized. Oversizing kills efficiency — so having a genuinely small unit available is a genuine advantage.
Build quality and warranty
Vaillant is a German manufacturer with over 140 years in heating. The build quality reflects that. Components are well-engineered, tolerances are tight, and the units are built to last. The 7-year warranty (extendable to 10 years with product registration) is the best standard warranty on this list and puts real skin in the game.
The honest downsides
This is the most expensive option here. At £10,000–£14,000 installed, it's £1,000–£2,000 more than a comparable Mitsubishi or Daikin. For some households that's meaningful money.
Installer availability is also worth thinking about. R290 requires specific F-gas handling qualifications — different to those needed for R32 systems. There are fewer trained installers in the UK right now. That's changing fast as the market moves, but if you're in a rural area, you may have to search a bit harder for someone qualified.
Who should buy this
- Anyone who wants the best-performing unit and has the budget to match.
- Long-term thinkers who want to own a system built around the refrigerant direction the industry is heading.
- Anyone with a noisy-unit concern — neighbours, garden, bedroom proximity.
Who should look elsewhere
- If you're budget-constrained, the Samsung EHS Mono gives you solid performance at significantly lower cost.
- If you're in a rural area with limited installer access, the Mitsubishi Ecodan's wider installer network may be more practical.
The Arotherm Plus is the benchmark. Everything else on this list is measured against it. See how it compares in our best heat pumps UK roundup, or check our heat pump costs guide for the full financial picture including the £7,500 BUS grant.