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Heat pumpsThe popular UK heat pump lines, compared on published specs
Every manufacturer claims efficiency. The useful comparison is the published numbers side by side, with the measurement conditions attached, because a SCOP quoted at 35C flow and one quoted at 65C flow are not the same claim.
Updated 4 August 2026 · written by the Clearline guidance team
How to read any heat pump spec sheet
Before the table, three rules. A SCOP figure is meaningless without the flow temperature it was measured at, because efficiency falls sharply as flow temperature rises. A noise figure is meaningless without knowing whether it is sound power or sound pressure, and if it is pressure, at what distance. And an output figure is meaningless without the air temperature it was rated at, because capacity falls as it gets colder outside.
Every number below carries its condition where the manufacturer publishes one. Where a figure comes from a review rather than a datasheet, it says so.
The badge matters less than the design
The Electrification of Heat trial monitored 742 heat pumps and found high variation in performance between installations, with a median in situ SPF of 2.80 across air source systems. That spread is wider than the spread between the units below. Choosing well matters. Designing well matters more.
The published specifications
| Line | Outputs | Refrigerant | Max flow temp | Published efficiency |
|---|---|---|---|---|
| Vaillant aroTHERM plus | 3.5, 5, 7, 10, 12 kW | R290, GWP of 3 | 75C | SCOP up to 5.03 |
| Mitsubishi Electric Ecodan R290 | 5 to 16 kW | R290 | 75C | SCOP 3.5 to 4.2 by size (review sourced) |
| Daikin Altherma 3 R | Standard monobloc range | R32 Bluevolution | Standard temperature | A+++ seasonal efficiency label |
| Daikin Altherma 3 H HT | Approx 11 to 13 kW, three classes | High temperature line | 70C | SCOP 4.71 at 35C |
| Samsung EHS Mono R290 Gen 7 | 5, 8, 12, 16 kW | R290 | Standard temperature | SCOP up to 4.84 at 35C on the 5 kW |
| Samsung EHS Mono HT Quiet | 8, 12, 14 kW | R32 | Hot water to 70C | SCOP 2.82, 3.01, 3.03 at 65C flow |
| Grant Aerona 290 | 4, 6.5, 9, 12, 15.5 kW single phase | R290 | Rated at 55C water flow | A+++ energy label |
| Ideal Logic Air | 4 to 10 kW | R32 | Standard temperature | SCOP 5.16 to 5.19 at 35C, 3.7 to 3.73 at 55C (review sourced) |
| Worcester Bosch Compress 7001i AW | 5, 7, 9, 13 kW | Manufacturer data sheet | Manufacturer data sheet | Manufacturer data sheet |
| Octopus Cosy 6 | See note | R290 | Own-brand monobloc | Real world SCOP up to 4.12 claimed (review sourced) |
Grant Aerona 290 outputs are each rated at minus 5C air temperature and 55C water flow, which is a colder and more demanding basis than many nominal figures. Octopus Cosy 6 nominal output figures vary between sources, so we do not publish a kW claim for it here: check the current Octopus datasheet. Blank cells mean the manufacturer publishes the figure but we have not verified it directly.
The R290 shift, and why it matters to you
The clearest market pattern in 2026 is refrigerant. Vaillant, Mitsubishi Electric, Samsung, Grant and Octopus all now lead with R290, which is propane, quoted by Vaillant at a global warming potential of 3. Daikin's mainstream Altherma 3 R uses R32, and Samsung keeps R32 on its high temperature Mono HT Quiet line.
The homeowner consequence is temperature. R290 units reach 70 to 75C flow, which is what makes keeping most of your existing radiators viable and what lets the heat pump handle cylinder hot water without leaning on an immersion heater. Vaillant states directly that the aroTHERM plus reaching 75C allows cylinder hot water without an immersion top up for legionella protection. That is a real running cost difference, not a marketing point.
High temperature capability is not a licence to run hot
A unit that reaches 75C should still be designed to the lowest flow temperature your emitters allow. Samsung's own numbers show the penalty: SCOP up to 4.84 at 35C flow against 2.82 to 3.03 at 65C. Buy the capability as a safety net, then design so you rarely use it.
Cold weather operation
Three of the lines publish an operating floor well below anything the British climate produces. Vaillant quotes the aroTHERM plus as operating down to minus 25C. The Mitsubishi Electric Ecodan R290 datasheet quotes the same minus 25C. Daikin quotes operation down to minus 25C on the Altherma 3 R.
Grant takes a different and arguably more honest approach with the Aerona 290, rating each output at minus 5C air temperature and 55C water flow rather than at a flattering mild condition. When you compare kW figures across brands, check what condition each one was measured at before concluding one unit is bigger than another.
Wondering which of these would actually suit your property and your radiators? The free remote design call answers that without a sales pitch.
Get your free quote →Noise, and why the figures do not compare directly
Manufacturers publish either sound power, which is the total acoustic energy the unit emits, or sound pressure, which is what you would measure at a stated distance. They are different measurements and comparing one against the other tells you nothing.
- Vaillant claims sound pressure below 30 dB(A) at 3 metres for the aroTHERM plus.
- Daikin quotes the Altherma 3 H HT at 38 dB(A) sound pressure at 3 metres in standard mode, and 35 dB(A) in low sound mode.
- Samsung quotes a 35 dB(A) quiet mode on the EHS Mono R290, and a four step quiet mode down to 35 dB(A) on the Mono HT Quiet.
- Mitsubishi Electric standard Ecodan models are reported at around 55 dB(A) sound power, with Ultra Quiet PUZ variants at 45 to 48 dB, both review sourced rather than taken from a manufacturer datasheet.
What actually governs whether a unit can go where you want it is not the datasheet, it is the MCS 020 (a) sound calculation, which must show 37 dB(A) or lower at the assessment position of the nearest noise sensitive premises. That calculation combines the unit's rating with distance, reflecting surfaces and the position of the neighbour's window. It is set out in heat pump noise and planning rules.
What to actually compare when you get quotes
- The design flow temperature the quote assumes, because it changes efficiency more than the brand does.
- The SCOP at that flow temperature, not the headline SCOP at 35C.
- The sizing basis, checked against the room by room heat loss calculation rather than the size of your old boiler.
- The MCS 020 (a) sound calculation result at the proposed position.
- The warranty terms and the availability of local service engineers for that brand, which matters more in year eight than in year one.
None of these units is a bad product, and the honest conclusion from the trial data is that the installation team's design decides your outcome far more than the badge does. That is why MCS certification and the survey get more space on this site than brand comparisons do.
Every county page on this site carries a local calculator and the current grant position, so start at our coverage map. The full heat pumps guide covers the rest of the system, and if you are weighing up solar panels alongside it, the combined electrical picture is worth planning in one pass.
Clearline does not sell, supply or endorse any product named here, and does not install. Installations are carried out by an MCS-certified installation team for your area. Specifications are taken from manufacturer pages and datasheets except where marked review sourced, and were checked on the date shown.
Comparison questions, answered
Which is the best air source heat pump in the UK?
There is no single answer, and the field data argues the question is less important than it looks. The Electrification of Heat trial found high variation in performance between installations of similar equipment, with a median in situ SPF of 2.80. Design quality, sizing and flow temperature move your bill further than the choice between these brands.
What is the difference between R290 and R32?
R290 is propane, quoted by Vaillant at a global warming potential of 3, and it enables the 70 to 75C flow temperatures that make radiator retrofits and immersion-free hot water viable. R32 remains in use across mainstream lines including the Daikin Altherma 3 R and the Ideal Logic Air. The practical difference for a homeowner is the maximum flow temperature available.
Why do SCOP figures vary so much between brands?
Mostly because they are measured at different flow temperatures. Ideal quotes 5.16 to 5.19 at 35C flow but 3.7 to 3.73 at 55C for the same units, and Samsung quotes up to 4.84 at 35C against 2.82 to 3.03 at 65C. Always check the condition attached to the number before comparing two brands.
Is the Octopus Cosy 6 a rebadged unit?
It is described as Octopus Energy's own-brand R290 monobloc, with a compact footprint of 855mm by 1125mm and a real world SCOP of up to 4.12 claimed in a review. Nominal output figures vary between sources, so confirm the current kW rating against the Octopus datasheet before relying on it.
Does Grant really make a 15.5 kW domestic unit?
Yes. The Aerona 290 range runs 4, 6.5, 9, 12 and 15.5 kW single phase, each rated at minus 5C air temperature and 55C water flow, and the 15.5 kW is sold through Octopus Energy for larger homes. Rating at minus 5C is a more demanding basis than many nominal figures, so compare like with like.
How do I compare noise figures between brands?
Carefully, because manufacturers publish sound power and sound pressure and the two are not interchangeable. Sound pressure figures also depend on the stated distance. For planning purposes the number that counts is the MCS 020 (a) calculation result at your neighbour's assessment position, which must be 37 dB(A) or lower.
See the numbers next: Duracell Dura16, installed, or what a battery costs.
Figures and specifications in this guide are sourced below and were checked on the date shown. Rates and product specifications change; we confirm the current picture on your free design call.
Sources
- Vaillant, aroTHERM plus product and specification pages: outputs, R290 with GWP of 3, SCOP up to 5.03, 75C flow, minus 25C operation, sound pressure below 30 dB(A) at 3 metres vaillant.co.uk
- Mitsubishi Electric Ecodan R290 datasheet (distributor copy): 5 to 16 kW outputs, 75C flow, minus 25C operation saturnsales.co.uk
- Solarinfo and Heatable, Mitsubishi Ecodan reviews (secondary): SCOP 3.5 to 4.2 by size, sound power figures, Ultra Quiet PUZ variants solarinfo.uk
- Daikin, Altherma 3 R product page and Altherma 3 H HT product page and installer brochure: R32 Bluevolution, A+++ label, minus 25C operation, 70C flow, SCOP 4.71 at 35C, 38 dB(A) and 35 dB(A) sound pressure at 3 metres daikin.co.uk
- Samsung Climate Solutions, EHS Mono R290 and EHS Mono HT Quiet product pages: capacities, SCOP up to 4.84 at 35C, SCOP 2.82 to 3.03 at 65C, 35 dB(A) quiet modes samsung-climatesolutions.com
- Grant UK, Aerona 290 range page and technical document rev 1.8, April 2026: outputs rated at minus 5C air and 55C flow, R290, A+++ label grantuk.com
- Ideal Logic Air brochure and distributor listing, with review-sourced datasheet SCOP figures dwellow.co.uk
- Worcester Bosch, Compress 7001i AW product page and technical data sheet: 5, 7, 9 and 13 kW outdoor units worcester-bosch.co.uk
- Future Heat, Octopus Cosy 6 review (secondary): own-brand R290 monobloc, 855mm by 1125mm footprint, claimed real world SCOP up to 4.12 futureheatltd.co.uk
- Energy Systems Catapult, Electrification of Heat performance data: median in situ SPF 2.80, variation between installations es.catapult.org.uk
- MCS 020 (a), Air Source Heat Pump Sound Calculation for Permitted Development Installations, Issue 1.0, July 2025 mcscertified.com
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