Grant Aerona³ 290 vs Mitsubishi Ecodan
A UK retrofit-focused comparison between Grant’s R290 retrofit performer and Mitsubishi’s long-established Ecodan platform. We prioritise real outcomes: comfort, running costs, noise placement, support confidence and value — assuming correct heat loss and commissioning.
Reviewed for UK retrofit relevance. Read How we score.
Score snapshot
Scores assume correct heat loss, emitter sizing and commissioning. In real UK installs, installer quality often outweighs brand differences.
Key differences in 60 seconds
- Positioning: Grant is a top-tier retrofit value performer; Ecodan is the mainstream UK “safe choice”.
- Support confidence: both strong — Ecodan edges on ecosystem depth; Grant is highly trusted in practical UK retrofits.
- Efficiency reality: both can be excellent — flow temperature targets decide outcomes more than brand.
- Decision rule: choose Grant for top-tier value; choose Ecodan for mainstream familiarity and service pathways.
In most homes, the best “upgrade” isn’t the brand — it’s better design, correct emitters and proper commissioning.
Choose Grant if… / Choose Ecodan if…
Choose Grant if…
- You want top-tier retrofit value
- You prefer practical, straightforward systems
- You want strong UK-focused support
- Your installer regularly fits Grant R290 systems
Choose Mitsubishi Ecodan if…
- You want the mainstream UK safe choice
- Installer familiarity and service pathways matter most
- You want predictable behaviour and broad support coverage
- You’re less concerned about “premium feel” and more about ecosystem depth
Retrofit reality
Both platforms can deliver excellent comfort and running costs in UK retrofits — but neither can overcome poor design. The most important factor is whether your home can deliver heat at sensible flow temperatures.
- Undersized emitters: higher flow temps, higher bills, less stable comfort.
- Good emitter capacity: lower flow temps, better efficiency and stability.
- Commissioning: often decides whether the homeowner loves or hates the system.
If your quote doesn’t include room-by-room heat loss and an emitter schedule, treat that as a bigger risk than brand selection.
Efficiency and flow temperature targets
Both can be efficient when designed for low/medium flow temperatures. The biggest efficiency differences in real homes come from flow temperature targets and emitter sizing — not the logo on the outdoor unit.
HeatPick tip
Ask: “What flow temperature are you designing for, and which radiators must change to achieve that?”
Noise and placement
Noise outcomes are mostly placement and mounting. Boundary distance, mounting surface, vibration isolation and commissioning choices often matter more than brochure differences.
If you’re on a tight plot, insist on a placement plan before signing anything.
Controls and day-to-day usability
Grant is generally “straightforward and practical”. Ecodan is reliable but can feel more functional than polished. In both cases, setup and handover decide whether it feels simple or confusing.
- Get your key settings in writing (weather curve, limits, DHW schedule).
- Ask what you should and shouldn’t change as a homeowner.
- Make sure weather compensation is configured and explained.
Support and ownership confidence
Ecodan’s advantage is the depth of UK installer familiarity and servicing pathways. Grant’s advantage is strong UK-focused practicality and a reputation for delivering retrofit outcomes reliably.
In practice, the biggest support variable is still your installer’s aftercare and willingness to optimise post-install.
Value
Grant often wins on value within the upper tier: excellent retrofit outcomes without maximum premium pricing. Ecodan can be great value if you prioritise the mainstream ecosystem and want the lowest-risk servicing pathway.
The best value move either way is paying for proper design up front to avoid expensive rework later.
Common mistakes (that make any heat pump look bad)
- No room-by-room heat loss and emitter schedule
- Trying to keep all radiators and compensate with high flow temperatures
- Weather compensation not commissioned or explained
- Outdoor placement decided late and causes noise issues
- No homeowner handover or documentation of settings
Questions to ask your installer (for this comparison)
- Which of these platforms do you install and service most often — and why?
- What flow temperature target are you designing for, and which emitters must change to hit it?
- What does commissioning day include, and what evidence do I receive?
- Where will the outdoor unit go, and how are noise/boundary constraints handled?
- If comfort or bills aren’t right, what is your aftercare and optimisation process?
Decision matrix
Not sure? Use the Home Check to narrow the most realistic next step.
How HeatPick approaches this
Method
- UK retrofit-first: we prioritise real installation outcomes.
- We score using weighted criteria (performance, efficiency, support, value, noise).
- We assume correct heat loss, emitter sizing and commissioning.
Read more: How we score.
Important
- This page is guidance, not a substitute for a room-by-room heat loss survey.
- Installer quality and commissioning can outweigh brand differences.
- Noise outcomes are mostly placement and mounting dependent.
FAQs
Is Grant better than Ecodan?
Not universally. Grant often wins on retrofit value, while Ecodan often wins on mainstream UK ecosystem depth. Installer quality matters more than the badge.
Which is cheaper to run?
In a correctly designed low/medium flow system, both can be efficient. Running costs are usually dominated by design targets, emitter capacity and commissioning.
Do I need radiator upgrades with either?
Often yes in UK retrofits. A room-by-room heat loss and emitter schedule gives the real answer, regardless of brand.
Is the Ecodan app experience a big issue?
It’s functional rather than premium. Many owners are fine with it, and setup/handover matters more than the interface.
What’s the best way to choose?
Choose the best installer with the strongest design and commissioning process, then choose the platform they’re most experienced with.
Verdict
Choose Grant Aerona³ 290 if you want top-tier retrofit value and strong UK practicality. Choose Mitsubishi Ecodan if you want the mainstream UK safe choice backed by deep installer familiarity and servicing pathways. Either way, system design and commissioning will matter more than the badge.