Daikin Altherma 3 vs Mitsubishi Ecodan: Two Japanese Giants Compared
Daikin and Mitsubishi are two of the most respected names in heat pumps globally, and both make excellent products for UK homes. If you're comparing these two, you're already in good territory. You're not going to end up with a bad heat pump either way. The question is which one is right for your specific situation.
Here's my honest take: trust your installer's recommendation more than this comparison. But let me explain why, and what the real differences are.
The Specs Side by Side
| Feature | Daikin Altherma 3 | Mitsubishi Ecodan |
|---|---|---|
| Headline efficiency (brochure) | Energy label up to A+++. Daikin UK publishes no per-model COP or SCOP | SCOP 4.49–4.62 on the R290 range |
| What you'll actually get | A seasonal COP around 3.3–3.5 | A seasonal COP around 3.3 |
| Refrigerant | R32 | R32 |
| Cold weather performance | Excellent | Very good |
| Installed cost | £9,000–£13,000 | £9,000–£13,000 |
| Unit size | Compact: good for smaller spaces | Standard: various sizes available |
| UK installer base | Large and growing | Very large: market leading |
| Track record in UK | Strong | Excellent: 10+ years |
| Warranty | 2 years, 5 with Stand By Me registration, 7 via a Sustainable Home Expert | 3 years, up to 7 through a Business Solutions Partner |
| Controls/smart integration | Daikin Onecta app | MELCloud app |
Where Daikin Pulls Ahead
Daikin's advantage isn't the headline number, because Daikin doesn't publish one. Its UK product pages carry an energy label and an operating envelope and nothing else: no COP, no SCOP, per model. What it does publish is the envelope, and it's a good one. Operation down to -28°C on the Altherma 3 H HT and H MT F, and -25°C on the Altherma 3 R F. When it's genuinely cold and the heat pump is working hardest, that's the spec that tells you something.
The one efficiency figure Daikin UK does put in writing is on a blog post, and it's refreshingly unflattering: "Daikin's standard heat pumps run at 3.6 SCOP". Compare that with the 4.5 to 5.4 its competitors advertise and you get a fair sense of how much of the gap between these brands is engineering and how much is marketing.
One correction while we're here, because we had it wrong and so does most of the internet: "flash injection" is Mitsubishi's term, used for its Zubadan compressors. It isn't Daikin's technology and it isn't what makes the Altherma good in the cold. Both manufacturers use enhanced vapour injection of one sort or another. The marketing names differ, the physics doesn't.
In practice, this is most relevant if you're in a colder part of the UK: northern England, Scotland, elevated areas. If you're in the south of England where temperatures rarely drop below -5°C, the advantage is real but less dramatic in day-to-day use.
The Daikin Altherma 3 is also notably compact. If you have a tighter space for the outdoor unit (a small side return, a narrow passage, a compact garden), the Daikin's smaller footprint can be a genuine practical advantage.
Where Mitsubishi Pulls Ahead
Mitsubishi's strength is depth of experience and installer familiarity. The Ecodan has been in UK homes for over a decade. There are more trained Ecodan installers than for any other heat pump brand. That matters enormously.
A heat pump is a sophisticated piece of equipment. It needs to be sized correctly for your home, installed carefully, and commissioned properly, with the correct flow temperature, the right settings for your radiators or underfloor heating, and the controls configured well. An installer who has commissioned 200 Ecodans will do a better job than one who has done 20 Daikins, even if the Daikin is technically more efficient on paper.
Mitsubishi's real-world reliability data across UK installations is also very strong. When you're spending £10,000+ on a heating system, knowing that thousands of similar systems are running well in similar homes is genuinely reassuring.
The Apps: Daikin Onecta vs Mitsubishi MELCloud
Both manufacturers have invested in smart home controls. Daikin's Onecta app has improved significantly in recent years and is now genuinely good. You can set schedules, monitor performance, and adjust temperatures remotely. MELCloud, Mitsubishi's equivalent, is reliable and widely used, though some users find the interface less intuitive.
Neither is dramatically better than the other. Both work well with smart tariffs and home automation systems. Don't let the app be a deciding factor.
The Price Is Essentially the Same
Unlike the Vaillant vs Mitsubishi comparison, where there's a meaningful price difference, Daikin and Mitsubishi come in at very similar costs. You're typically looking at £9,000–£13,000 installed for either, depending on the size of system, any radiator upgrades needed, and your location. This makes the decision genuinely close.
So Which One Should You Get?
This is where I'll be direct: ask your installer, and trust the answer. Here's why that's not a cop-out.
The difference in real-world performance between a well-installed Daikin and a well-installed Mitsubishi is marginal. Both will keep your house warm, both will give you a seasonal COP comfortably above 3 in normal UK conditions, and both are reliable. Put a number on it: a house needing 12,500 kWh of heat a year costs £997 to heat at a seasonal COP of 3.3 and £940 at 3.5, on the current 26.32p cap. That's £57 a year, which is less than the error bar on any efficiency estimate and a lot less than the difference a good commissioning job makes.
What makes a genuinely large difference is how well your system is designed and installed. Flow temperature settings, radiator sizing, cylinder configuration, controls setup: these choices affect your bills far more than which brand is on the outdoor unit.
If your installer says "I've done 150 Ecodans and I know them inside out, I'd recommend Mitsubishi," go with Mitsubishi. If they say "I'm fully trained on Daikin and I think the Altherma 3 is the best product on the market right now," go with Daikin.
One Exception: Cold Climates
If you're in a genuinely cold part of the UK and you get prolonged spells below -5°C, the Altherma's low-ambient envelope is a real advantage. Ask specifically for the HT or MT variant, which is where the -28°C figure applies; the Altherma 3 R stops at -25°C. And ask to see the capacity and COP at A-7/W35 for the exact model on the quote, which Daikin keeps in the technical data sheets rather than on the website.
The Verdict
Both are excellent. Daikin edges ahead on cold-weather envelope. Mitsubishi edges ahead on installer familiarity, track record, and on actually telling you what its machines do. The price is the same. Follow your installer's lead. Their experience with the specific product matters more than anything on a spec sheet. For detailed reviews of each, see our Daikin Altherma 3 review and Mitsubishi Ecodan review. For the full brand ranking, see our best heat pumps UK guide.