Octopus: 99.6 percent of its heat pump owners pay less than gas

What the data shows

Source: Octopus Energy, 2 September 2026.

Octopus Energy released figures on 2 September 2026 stating that 99.6 percent of its Cosy heat pump customers pay less to heat their homes than they would with a gas boiler. The figure is drawn from the company's public Cosy fleet performance dashboard, which uses anonymised aggregate data from Cosy heat pump systems across Great Britain between 1 September 2025 and 31 August 2026, alongside Cosy Octopus smart tariff rates over the same period. The dashboard is published by Octopus itself, and the comparison is made against the cost of heating the same homes with a gas boiler.

The efficiency numbers behind the claim are central to how the saving arises. Octopus says Cosy systems generated more than 4 kWh of heat per kWh of electricity, a coefficient of performance of 3.97. That is measured against a generally accepted figure of 0.85 for a gas boiler, which makes the heat pump about 4.7 times more efficient in converting energy into heat. On that basis, Octopus says customers on the Cosy Octopus smart tariff save an average of 227 pounds a year compared with heating with a gas boiler. The company also says more than 550,000 people enquired about a heat pump from Octopus in the past year.

Rebecca Dibb-Simkin, Chief Product Officer at Octopus Energy, said: "For years, sceptics have said heat pumps are expensive to run, so we took the groundbreaking decision to put all our Cosy heat pump real-world performance online." The Cosy heat pump is designed and manufactured in the UK and can be updated remotely, and a recent update added a quiet Hush Mode. Octopus Energy designs, sells and installs the Cosy heat pump and sells the Cosy tariff, and Octopus Energy Group serves 11 million households globally.

The VAT claim

Octopus says VAT on electricity is set to fall to 0 percent from 1 October 2026 under a government intervention, while gas remains at 5 percent. That is Octopus's claim, and it should be checked against GOV.UK for the official notice before being treated as settled. The timing matters because Ofgem's energy price cap rose from 1 October 2026, and Octopus refers to the latest increase in its release. A change in VAT on electricity would affect the running cost comparison directly, because the saving figures rest on the unit rate a household actually pays.

For a household weighing a heat pump, the VAT position is one variable among several. The 227 pounds a year average saving is calculated on Cosy Octopus tariff rates, so any change to electricity VAT would alter the arithmetic in one direction, while the gas side would remain at 5 percent on Octopus's account. Until the official notice is published, the VAT element of the claim is best treated as an Octopus statement rather than a confirmed change in the law. The same caution applies to the headline 99.6 percent figure, which is a snapshot of one company's fleet on one company's tariff.

KT analysis: what the 99.6 percent rests on

The 99.6 percent figure describes Octopus customers on Octopus's own smart tariff with Octopus-installed pumps. That is a best case for a well-installed system: the pump, the installation and the tariff are all supplied by the same company, and the performance data comes from that company's own dashboard. A household on a standard variable tariff, or with a poorly sized system, would see a smaller gap between heat pump and gas running costs. The seller is the source, and the comparison assumes the Cosy tariff throughout.

The efficiency gap itself is the strongest part of the case. A coefficient of performance of 3.97 against 0.85 for gas is a wide margin, and it is the reason a heat pump can cost less to run even when electricity costs more per unit than gas. But that margin depends on installation quality, system sizing and how the home is heated. A heat pump that is undersized for the property, or fitted without adequate insulation and radiator sizing, will not reach the performance in the dashboard. The 227 pounds a year average saving is an average across the fleet, not a guarantee for any single home.

Upfront cost remains the barrier. The Boiler Upgrade Scheme in England and Wales offers a 7,500 pound grant towards an air source heat pump installed by an MCS-certified installer. That grant reduces the initial outlay but does not remove it, and the scheme does not cover every property type or every part of the UK in the same way. Homes also need adequate insulation and radiator sizing before a heat pump performs as the data suggests. The running cost case and the upfront cost case are separate questions, and the Octopus figures address only the first.

What it means for a household weighing a heat pump

Ask any installer for the design coefficient of performance for the specific property, and for the tariff assumption behind any saving claim. A saving quoted against a smart heat pump tariff will not apply to a household that stays on a standard variable rate. Compare the electricity unit rate on a smart heat pump tariff with the standard variable rate before treating a running cost figure as relevant. Check MCS certification for the installer, because the 7,500 pound Boiler Upgrade Scheme grant in England and Wales depends on it.

Treat software features such as Hush Mode as secondary to sizing and insulation. The Octopus data covers a fleet on the Cosy tariff, and the company sells and installs both the pump and the tariff. The 99.6 percent figure and the 227 pounds a year average are useful as a signal that heat pumps can run cheaper than gas in the right setup, but the household level questions are about the property, the tariff and the upfront cost. The VAT claim should be checked against GOV.UK once the official notice appears.

Source: Octopus Energy release, 2 September 2026.

Related coverage on Kael Tripton: Boiler Upgrade Scheme: £7,500 and £9,000 Heat Pump Grants, Heat Pump Grant Rises to £9,000 from 21 July: Who Qualifies and How to Apply, Energy Price Cap Rises to £1,723 From October 2026, Energy Price Cap Explained: Current Rates and Next Change, British Gas Boiler Cover Review UK: Homecare Plans, Costs and FOS Data.

Frequently asked questions

What does the 99.6 percent figure actually measure?

It is the share of Octopus Cosy heat pump customers who pay less to heat their homes than they would with a gas boiler, according to Octopus's public Cosy fleet performance dashboard. The dashboard uses anonymised aggregate data from Cosy heat pump systems across Great Britain between 1 September 2025 and 31 August 2026, and Cosy Octopus smart tariff rates over the same period.

How much can a Cosy heat pump customer save?

Octopus says customers on the Cosy Octopus smart tariff save an average of 227 pounds a year compared with heating with a gas boiler. That is an average across the fleet on that tariff, not a guaranteed figure for an individual home.

What efficiency figures sit behind the claim?

Octopus says Cosy systems generated more than 4 kWh of heat per kWh of electricity, a coefficient of performance of 3.97. That is compared with a generally accepted 0.85 for a gas boiler, which is about 4.7 times the efficiency.

Is the VAT change on electricity confirmed?

Octopus says VAT on electricity is set to fall to 0 percent from 1 October 2026 under a government intervention, while gas remains at 5 percent. This is Octopus's claim and should be checked against GOV.UK for the official notice.

What grant is available for a heat pump?

The Boiler Upgrade Scheme in England and Wales offers a 7,500 pound grant towards an air source heat pump installed by an MCS-certified installer.