Octopus Energy occupies a position no other heat pump brand in the UK holds. It manufactures the unit, employs the installers who fit it, and sells you the electricity that runs it afterwards. That vertical integration is the whole argument for and against them.
It also produces something the rest of the industry does not offer: published performance data from every heat pump they have installed, measured from real metered consumption rather than a laboratory. That single dashboard makes Octopus the easiest heat pump in Britain to assess honestly.
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- Octopus Energy’s typical price is £4,459 after the £7,500 grant - their median post-survey figure for quotes between September 2025 and February 2026, with the grant applied by them rather than claimed by you
- Measured fleet efficiency is 3.77, higher than the lab ratings - real-world performance across every Cosy customer usually falls below spec, and here it does not
- Three units cover most homes: 5.2, 8.1 and 10kW upward - with lab SCOP of 3.4, 3.6 and 3.9 at 50°C flow
- The 8 year warranty is among the longest offered as standard - no installer-tier upgrade needed to reach it
- Noise is the real weak point at 58 to 59 dB(A) on the Cosy 6 - materially louder than the quietest competitors, which matters on a terrace
What Octopus Energy Charges
Octopus states a typical price of £4,459. That figure is already net of the £7,500 Boiler Upgrade Scheme, and it is the median post-survey price across their quotes between 1 September 2025 and 28 February 2026.
Two details matter more than the number. First, Octopus applies the grant themselves rather than leaving you to claim it, which removes the part of the process most likely to go wrong. Second, it is a post-survey median, so it reflects what people actually paid after their property was assessed, not a headline teaser.
Octopus Energy positions this against a £5,600 national average. Treat that comparator with care: it is their characterisation of the market they compete in, not an independently verified figure. For context on what the wider market charges, our air source heat pump cost guide works through installed pricing across brands.
The £7,500 is the standard Boiler Upgrade Scheme rate, rising to £9,000 off the gas grid on oil or LPG. Our guide to heat pump grants covers eligibility and the exclusions that catch people out.
The Cosy Range and Which Size You Need
Octopus sells three units. They are deliberately a narrow range, covering the bulk of UK housing without the specification sprawl of the traditional manufacturers.
| Model | Heat output | SCOP at 50°C | Sound | Size (W x H x D) |
|---|---|---|---|---|
| Cosy 6 | 5.2–5.6 kW | 3.4 | 58–59 dB(A) | 855 x 1125 x 595mm |
| Cosy 9 | 8.1–8.7 kW | 3.6 | 56–57 dB(A) | 855 x 1375 x 595mm |
| Cosy 12 | 10–11.2 kW | 3.9 | 61 dB(A) | 855 x 1375 x 595mm |
Note that efficiency rises with size across the range, which is the opposite of what buyers often assume. The Cosy 12 is the most efficient unit on paper and the Cosy 6 the least. Sizing is still set by your property’s heat loss rather than by chasing the better SCOP, and our heat pump sizing guide explains the calculation an installer must perform.
Hot water recovery is quick. A 180 litre cylinder reheats in 70 minutes on the Cosy 6, falling to 40 minutes on the Cosy 12. A 300 litre cylinder takes 125 minutes down to 70 minutes across the same range.
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Real-World Performance: The Part Nobody Else Publishes
Every heat pump manufacturer quotes a SCOP from laboratory testing. Almost none publish what their units actually achieve in customers’ homes, and the honest industry position is that real-world performance usually lands below the lab figure.
Octopus publishes a live dashboard drawn from the metered consumption of every Cosy heat pump customer, refreshed weekly. For the year to 30 August 2026 it reports an average seasonal performance factor of 3.77, covering both heating and hot water.
That number is the most interesting thing about this product. It sits at or above the lab SCOP of the individual units, which is unusual and points to installation quality rather than to the hardware. A heat pump’s real efficiency is decided by flow temperature, emitter sizing and controls, all of which Octopus controls because it does the install itself.
| Outside temperature | Median COP |
|---|---|
| −5°C to 0°C | 2.72–3.11 |
| 0°C to 5°C | 3.11–3.64 |
| 5°C to 12°C | 3.64–4.34 |
| 12°C to 15.5°C | 4.23–4.36 |
The cold-weather column is the one to read carefully. At below freezing the units deliver roughly 2.7 to 3.1 units of heat per unit of electricity, comfortably better than any resistive electric heating and still ahead of gas on carbon, though the running-cost gap narrows sharply. Our heat pump versus gas boiler comparison works through where that leaves you on cost.
The Cosy Octopus Tariff
Because Octopus also supplies your electricity, they offer a tariff built around heat pump usage. Cosy Octopus gives three cheap windows a day: 04:00 to 07:00, 13:00 to 16:00 and 22:00 to 00:00. Those windows are priced 51% below the day rate for your region, and the peak period sits 50% above it.
Octopus publishes the tariff only as a percentage of your regional day rate, with the absolute pence per kWh behind a postcode lookup, so we are not going to quote a headline rate that will be wrong for most readers. Eligibility needs an Octopus account, a smart meter and a heat pump, electric radiator or electric boiler at the property.
The structure rewards running the heat pump hard during cheap windows and coasting through peak, which suits a well-insulated home with a decent thermal buffer far better than a draughty one. That is the same conclusion our heat pump running costs guide reaches about specialist tariffs generally.
Noise: The Honest Weak Point
The Cosy 6 is rated at 58 to 59 dB(A) and the Cosy 12 at 61 dB(A). For comparison, the Vaillant aroTHERM Plus is Quiet Mark certified at 54 dB, and several units in our best air source heat pump brands roundup sit in the low 30s.
Decibels are logarithmic, so the gap is larger than it reads. On a detached property with garden space this is unlikely to matter. On a terrace, in a close-packed estate, or anywhere a planning officer may take an interest in the boundary noise limit, it is the first thing to check before committing.
How Octopus Compares
Comparing heat pumps on headline SCOP is the most common mistake buyers make, and it is worth understanding before you put Octopus next to anyone else.
SCOP is quoted at a specific flow temperature, and the number rises sharply as that temperature falls. Octopus publishes 3.4 to 3.9 at 50°C. Vaillant publishes up to 5.03 at 35°C. Those are not comparable figures, and a brand quoting a large number at 35°C is not necessarily more efficient in your house than one quoting a smaller number at 50°C.
What matters is the flow temperature your emitters actually need. A home keeping its existing radiators may need 50°C or higher, in which case a 35°C rating tells you very little. A home with underfloor heating or upsized radiators can run at 35°C and will see the higher number.
Any SCOP figure without a flow temperature attached is marketing rather than specification. Ask every installer what flow temperature their quoted efficiency assumes, and what flow temperature your property will actually run at.
On the comparisons that are like for like, Octopus leads on warranty at 8 years standard, and on transparency by a distance, because nobody else publishes measured fleet data at all. It trails clearly on noise. On price the picture is muddied by Octopus quoting post-grant and most manufacturers quoting pre-grant or not at all, which is why our brand comparison normalises them.
Who Should Buy One
Octopus suits people who want the whole thing handled and are willing to accept a narrow product range in exchange. The grant is applied for you, the install is done by the company that built the unit, and the tariff is designed around the appliance. For a mainstream retrofit that is a strong package.
It suits you less if noise is a constraint, if you want a specific manufacturer’s hardware, or if your property needs a high flow temperature because the radiators are staying as they are. In those cases a wider search is worth the effort, and if you have the land, a ground source system reaches efficiencies no air source unit will match.
Our Verdict
Octopus Energy Cosy heat pump review: £4,459 typical after the grant, a measured fleet efficiency of 3.77, and the noise figure worth checking first.
The Octopus Cosy scores 8.7 out of 10. Measured fleet performance of 3.77, a keen post-grant price and an 8 year warranty make it the strongest mainstream package in the UK right now. Noise is the one thing that will rule it out, and it rules it out completely rather than partially.
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How We Researched This Review
Specifications, pricing, warranty and tariff structure come from Octopus Energy’s own product, performance and tariff pages, checked on 1 September 2026. The efficiency figures come from their published fleet dashboard, which draws on metered consumption from every Cosy customer over the year to 30 August 2026 and refreshes weekly.
We have not repeated the parts and labour warranty split that circulates in search results, because it does not appear on Octopus’s own product page. Where Octopus publishes a figure about its competitors rather than about itself, we have attributed it to them rather than presenting it as market fact.
