Cosy Octopus for heat pumps: how it works and what it costs

How Cosy works

Cosy has three rates, and the times are the same every day:

• Cosy hours (cheapest): 04:00 to 07:00, 13:00 to 16:00 and 22:00 to midnight, eight hours in total
• Peak (dearest): 16:00 to 19:00
• Standard: every other hour of the day

The rates apply to everything in the house, not just the heat pump. Octopus describes the Cosy hours as 51% cheaper than the day rate in your region and the peak as 50% above it.

To be eligible you need:

• a heat pump (air or ground source), electric radiators or an electric boiler
• a SMETS2 smart meter, or one of the SMETS1 types Octopus can connect to
• to be an Octopus customer

Octopus offers Cosy as a 12-month fix with a £50 exit fee, and as a flexible version with no exit fee whose rates can go up or down.

What it costs

Rates vary by region. These are the rates Octopus publishes for the Cosy 12-month fix available from 30 October 2026. VAT on home electricity is 0% from 1 October 2026 until 31 March 2027, so there's no VAT to add.

On 1 November 2026 the flexible version was cheaper in South Scotland, at 13.86p in the Cosy hours, 28.27p standard and 42.40p peak, with a 61.44p standing charge. Flexible rates move with the market, so that gap may not last. Octopus reprices the fix every few weeks, so check the rates for your own postcode before you switch.

A worked example

Octopus's Cosy page bases its own figures on a heat pump home using 5,877 kWh of electricity a year, 3,177 kWh of it for heating. Using that total, the South Scotland fixed rates and the GB average price cap:

• At the price cap the year costs about £1,747, standing charge included.
• With 60% of use in the Cosy hours and 5% in the peak, Cosy comes to about £1,574, around £170 less.
• With only 40% in the Cosy hours and 15% in the peak, Cosy comes to about £1,860, around £115 more.
• On the flexible rates the same two cases come to about £1,419 and £1,671.

These are my calculations from published rates, not an Octopus figure and not a promise of what you'll pay. What decides it is how much of your use you can keep out of 16:00 to 19:00.

Getting more of your use into the cheap hours

A heat pump runs for long stretches rather than in one overnight burst, which is why Home Energy Scotland notes that Economy 7 doesn't always suit them. Cosy's afternoon window helps here. The settings worth looking at are:

• heating the hot water cylinder in one of the Cosy windows rather than in the evening
• letting the house warm up a little more between 13:00 and 16:00 so the heat pump can ease off during the peak
• keeping the dishwasher, washing machine and any EV charging out of 16:00 to 19:00

How far you can push this depends on the heat pump's controls and how well the house holds heat. Your installer or the heat pump maker can tell you what scheduling the controls support.

Who it suits, and who it doesn't

It suits you if you have a heat pump with controls you can schedule, a hot water cylinder you can heat at set times, and not much else running in the early evening.

It is unlikely to suit you if a lot of your electricity goes on cooking, washing or EV charging between 16:00 and 19:00, or the heat pump has to run hard through the evening to keep the house warm. In those cases the peak rate takes back what the Cosy hours save.

Without a heat pump, electric radiators or an electric boiler you can't join Cosy, and Octopus's standard fixed tariffs or Agile are the ones to compare.