Vaillant aroTHERM Plus vs Mitsubishi Ecodan
Vaillant aroTHERM Plus vs Mitsubishi Ecodan: The Premium Heat Pump Shootout
If you've done any research on heat pumps in the UK, you've almost certainly come across these two names. Vaillant and Mitsubishi are the top of the market — both are excellent, both are widely installed, and both are approved for the Boiler Upgrade Scheme grant. So which one should you choose?
The honest answer is: you won't go wrong with either. But they have real differences, and depending on your situation, one is likely the better fit.
Specs at a Glance
| Feature | Vaillant aroTHERM Plus | Mitsubishi Ecodan |
|---|---|---|
| Peak COP | 5.1 | 4.6 |
| Refrigerant | R290 (propane — low GWP) | R32 |
| Noise level | 54dB | 45–62dB (model dependent) |
| Installed cost | £10,000–£14,000 | £9,000–£13,000 |
| Warranty | 7–10 years | 5–7 years |
| Installer network | Growing | Very large — well-established |
| Track record in UK | Newer to market | 10+ years of UK installations |
| Future-proofing | Excellent (R290 is future standard) | Good (R32 being phased down longer-term) |
The Case for Vaillant
On paper, Vaillant edges ahead. A COP of 5.1 is genuinely impressive — it means for every £1 of electricity you put in, you get £5.10 worth of heat out. That's better than most competitors at the same price point.
The bigger deal is the refrigerant. Vaillant's aroTHERM Plus uses R290 — propane — which has a global warming potential (GWP) of just 3. Compare that to R32, which has a GWP of 675. The EU and UK are moving towards natural refrigerants like R290. If you want a heat pump that's environmentally ahead of the curve and won't face regulatory complications in the future, Vaillant is the better choice.
The longer warranty — up to 10 years — is another mark in Vaillant's favour. That's a real statement of confidence in the product.
The Case for Mitsubishi
Mitsubishi has been installing Ecodan heat pumps in the UK for over a decade. That matters more than it sounds. There are thousands of trained Ecodan installers across the country, which means it's easier to find someone local who really knows the product inside out. That installer familiarity leads to better commissioning, better performance, and fewer problems.
Real-world data on the Ecodan is extensive. It performs well, it's reliable, and when something does go wrong, parts and expertise are readily available. Vaillant's aroTHERM Plus is newer to the UK market — the efficiency numbers are great, but you're relying on a shorter track record.
The Ecodan is also slightly cheaper to install in most cases, which gives you more room to invest elsewhere — better radiators, a hot water cylinder upgrade, or simply keeping more money in your pocket.
Noise: Does It Matter?
Both units produce some noise. The Vaillant aroTHERM Plus runs at a consistent 54dB. Mitsubishi's noise varies by model — quieter options sit around 45dB, louder ones hit 62dB. If noise is a concern (perhaps your outdoor unit will be near a bedroom window or close to a neighbour), check the specific Ecodan model your installer is proposing. The quietest Ecodan models are genuinely very quiet.
What Should You Actually Do?
Here's the practical advice: find a good installer first, then ask what they recommend. A heat pump is only as good as its installation. A perfectly specified Vaillant installed badly will underperform a well-installed Ecodan every time.
If your installer is highly experienced with Vaillant's aroTHERM Plus and enthusiastic about it, go with Vaillant. The efficiency and refrigerant advantages are real, and a confident installer will get the best out of it.
If your installer is primarily an Ecodan specialist — and many of the best heat pump engineers in the UK are — go with Mitsubishi. The track record is excellent and you'll benefit from their deep knowledge of the product.
If you're choosing between installers, and one quotes Vaillant while another quotes Mitsubishi, don't let the product be the deciding factor. Look at the installer's MCS certification, their reviews, and their commissioning process. That's what will make the difference to how warm your house is and how low your bills are.
The Verdict
Vaillant if you want the most efficient, future-proofed option and you can find a good installer who knows the product. Mitsubishi if you want a safe, proven choice with a massive installer network behind it. Genuinely, you won't regret either one. For detailed reviews, see our Vaillant Arotherm Plus review and Mitsubishi Ecodan review. For the wider picture, see our best heat pumps UK guide and heat pump costs guide.