Daikin Altherma vs Octopus Cosy: Which Air Source Heat Pump Is Better? (2026)
Quick Verdict
Daikin Altherma is the more efficient choice with a higher SCOP, meaning lower running costs over time.
Side-by-Side Comparison
| Feature | Daikin Altherma | Octopus Cosy |
|---|---|---|
| Installed price (before grant) | £7,000 - £14,000Lower | £8,000 - £12,000 |
| After £7,500 grant (illustrative, England and Wales) | £0 - £6,500 | £500 - £4,500 |
| SCOP (seasonal efficiency) | 4.2Higher | 4.1 |
| Max heat output | 14kWLarger homes | 9kW |
| Unit warranty | 5 years | 5 years |
| Compressor warranty | 5 years | 5 years |
| Noise level | 44dBQuieter | 45dB |
| Annual running cost (est.) | ~£595/yrLower | ~£610/yr |
| Refrigerant | Varies by model | Varies by model |
| Country | Japan | UK |
| UK brand | No | Yes |
| Best for | Buyers wanting proven mainstream hardware with plenty of competing quotes | Price-led switchers happy to go with one vertically integrated provider |
Specifications and pricing are indicative for the UK market as at June 2026. Post-grant figures illustrate the £7,500 Boiler Upgrade Scheme in England and Wales (Scotland uses the Home Energy Scotland grant and loan; Northern Ireland has no equivalent). Running costs assume ~10,000 kWh of heat a year at 25p/kWh (Ofgem cap average; changes quarterly). Confirm current models and exact pricing with your MCS-certified installer.
Price Comparison
Daikin Altherma starts from £7,000 installed before any support (indicative, June 2026), while Octopus Cosy starts from £8,000. That is a difference of roughly £1,000 at the entry level. Daikin Altherma is the more budget-friendly option upfront, though Octopus Cosy may claw some of that back through running costs over time. Both are installed prices in GBP with 0% VAT (until 31 March 2027) already applied. In England and Wales the £7,500 Boiler Upgrade Scheme grant comes off both equally, so the pre-grant difference carries straight through: illustratively £0 - £6,500 for Daikin Altherma and £500 - £4,500 for Octopus Cosy out of pocket. Your MCS-certified installer claims the grant for you.
Efficiency Comparison
SCOP (seasonal coefficient of performance) is the key efficiency metric for a heating heat pump: it measures how many kilowatt-hours of heat you get per kilowatt-hour of electricity across a whole heating season. Daikin Altherma reaches a SCOP of 4.2, while Octopus Cosy reaches 4.1. The Daikin Altherma is roughly 2% more efficient on this measure, which on our estimates is worth about £15 a year at Ofgem cap electricity prices, or approximately £150 over ten years. Real-world SCOP depends heavily on system design and flow temperature, which is what the MCS heat-loss survey is for.
Warranty Comparison
Daikin Altherma offers a 5-year unit warranty and 5-year compressor warranty. Octopus Cosy offers a 5-year unit warranty and 5-year compressor warranty. Both brands offer the same unit warranty length, so coverage is comparable; check what extended terms each installer can register. Workmanship cover for the installation itself comes separately from your installer and should be at least 12 months, in writing.
Noise Comparison
Noise matters in UK homes because the outdoor unit often sits close to a neighbour's boundary or a bedroom window, and siting is part of the installation assessment. Daikin Altherma operates from 44dB, while Octopus Cosy runs from 45dB. The Daikin Altherma is quieter at 44dB. At this level it is moderate, similar to a quiet conversation; ask the installer to position the unit away from bedroom windows and boundary walls.
Cold-Weather and Retrofit Suitability
Two things decide how well a unit suits an older UK home: cold-weather output and flow temperature. Daikin Altherma uses a refrigerant that varies by model, while Octopus Cosy uses a refrigerant that varies by model. Modern units from both brands hold useful output well below freezing. In the colder parts of the UK (Scotland and northern England in particular), frosty mornings trigger short defrost cycles that trim efficiency, so ask each installer for low-temperature output figures and take the MCS heat-loss survey seriously; radiator upsizing is more commonly recommended there so the system can run at efficient flow temperatures.
Pros and Cons
Daikin Altherma
Pros
- World's largest heat pump manufacturer
- High-temperature models suit older radiator systems
- Wide UK installer base
- Strong cold-weather output
- Competitive entry pricing
Cons
- Warranty shorter than some rivals unless extended
- Quality of install varies with such a large network - vet quotes carefully
Octopus Cosy
Pros
- Cheapest mainstream route to a heat pump (avg ~£4,460 post-grant via Octopus)
- UK-designed, end-to-end install by one company
- Tariff pairing cuts running costs
- Grant handled entirely for you
Cons
- Install only through Octopus (no independent quotes on the hardware)
- Newer hardware with a shorter track record
- Standard 5-year warranty
Which Should You Choose?
Choose Daikin Altherma if...
- You want a lower upfront cost (from £7,000 vs £8,000 before the grant)
- You want the best efficiency and lowest running costs (SCOP 4.2 vs 4.1)
- Quiet operation matters to you (44dB vs 45dB)
- You want lower estimated annual running costs (~£595/yr vs ~£610/yr)
Choose Octopus Cosy if...
- You want a UK brand with local manufacturing or headquarters behind it
The grant is the same, whichever brand you pick
Every air-to-water unit on this page qualifies for the £7,500 Boiler Upgrade Scheme grant in England and Wales (£9,000 for oil and LPG heated homes from 21 July 2026) when fitted by an MCS-certified installer, who claims it on your behalf so it comes straight off the quote. Scotland uses the Home Energy Scotland grant of up to £7,500 (£9,000 rural and island) plus an optional interest-free loan; Northern Ireland currently has no equivalent scheme. 0% VAT on residential installations applies UK-wide until 31 March 2027. Accurate as at June 2026.
Where are you?
See indicative costs and local installers for your area