Is a home battery worth it on Cosy Octopus?
Cosy Octopus is for homes heated by electricity — a heat pump, electric radiators or an electric boiler. It has three cheap windows (04:00–07:00, 13:00–16:00 and 22:00–00:00) and a dear peak from 16:00 to 19:00.
The tariff in brief
| Price pattern | Cheap 04:00–07:00, 13:00–16:00 and 22:00–00:00; peak 16:00–19:00. |
|---|---|
| Who can get it | Needs a heat pump, electric radiators or an electric boiler. |
| Octopus product code | COSY-22-12-08 |
| London unit rates | 14.8p / 30.2p / 45.4p per kWh |
| London standing charge | 44.4p per day |
Octopus public API, fetched 25 October 2026. Import prices shown with the normal 5% VAT (VAT is off bills from 1 October 2026 to 31 March 2027).
A day on this tariff in London
All 48 half-hours
| Time | p/kWh | Time | p/kWh |
|---|---|---|---|
| 00:00 | 30.2p | 12:00 | 30.2p |
| 00:30 | 30.2p | 12:30 | 30.2p |
| 01:00 | 30.2p | 13:00 | 14.8p |
| 01:30 | 30.2p | 13:30 | 14.8p |
| 02:00 | 30.2p | 14:00 | 14.8p |
| 02:30 | 30.2p | 14:30 | 14.8p |
| 03:00 | 30.2p | 15:00 | 14.8p |
| 03:30 | 30.2p | 15:30 | 14.8p |
| 04:00 | 14.8p | 16:00 | 45.4p |
| 04:30 | 14.8p | 16:30 | 45.4p |
| 05:00 | 14.8p | 17:00 | 45.4p |
| 05:30 | 14.8p | 17:30 | 45.4p |
| 06:00 | 14.8p | 18:00 | 45.4p |
| 06:30 | 14.8p | 18:30 | 45.4p |
| 07:00 | 30.2p | 19:00 | 30.2p |
| 07:30 | 30.2p | 19:30 | 30.2p |
| 08:00 | 30.2p | 20:00 | 30.2p |
| 08:30 | 30.2p | 20:30 | 30.2p |
| 09:00 | 30.2p | 21:00 | 30.2p |
| 09:30 | 30.2p | 21:30 | 30.2p |
| 10:00 | 30.2p | 22:00 | 14.8p |
| 10:30 | 30.2p | 22:30 | 14.8p |
| 11:00 | 30.2p | 23:00 | 14.8p |
| 11:30 | 30.2p | 23:30 | 14.8p |
The afternoon window lets a battery refill just before the peak, so even a small battery can cycle twice on some days. Heat pump homes use most in winter, when Cosy’s windows matter most.
What a battery saves on Cosy Octopus: four modelled homes
London prices, typical-household profiles (Elexon Profile Class 1 shape), battery 95% usable, 90% round trip. “Most to pay” is the 10-year price ceiling with capacity fading to 80%. Only electrically heated homes can join Cosy.
| Home | Bill, no battery | 5 kWh saves | 10 kWh saves | 13.5 kWh saves | Most to pay for 10 kWh |
|---|---|---|---|---|---|
| Typical home, 2,500 kWh a year | £876 | £284 | £284 | £284 | £2,588 |
| Home all day, 3,500 kWh | £1,157 | £392 | £392 | £392 | £3,563 |
| Electric car, 2,700 + 2,000 kWh | £1,230 | £307 | £307 | £307 | £2,795 |
| Heat pump, 2,700 + 3,500 kWh | £1,902 | £479 | £654 | £659 | £5,949 |
For comparison, the typical home pays £876 a year on Cosy Octopus without a battery; Flexible Octopus in London is 27.9p per kWh.
Cosy Octopus in every region
| Region | Standing charge, p/day | Cheapest rate | Dearest rate |
|---|---|---|---|
| A Eastern England | 54.26 | 14.8p | 45.4p |
| B East Midlands | 53.28 | 14.1p | 43.2p |
| C London | 44.41 | 14.8p | 45.4p |
| D Merseyside and North Wales | 70.08 | 15.5p | 47.5p |
| E West Midlands | 59.44 | 14.3p | 43.7p |
| F North East England | 63.74 | 14.2p | 43.4p |
| G North West England | 47.09 | 14.8p | 45.2p |
| H Southern England | 49.85 | 14.8p | 45.1p |
| J South East England | 54.82 | 15p | 45.8p |
| K South Wales | 57.08 | 14.8p | 45.3p |
| L South West England | 58.30 | 14.8p | 45.3p |
| M Yorkshire | 63.90 | 14.3p | 43.7p |
| N South and Central Scotland | 64.51 | 14.6p | 44.5p |
| P North Scotland | 58.04 | 14.7p | 44.9p |
Frequently asked questions
Is a home battery worth it on Cosy Octopus?
In Fortyeight’s model of a London home, a 10 kWh battery on Cosy Octopus saves about £284 a year for a typical 2,500 kWh home and up to £654 for the heavier users modelled. To pay back in 10 years it would need to cost under £5,949 at best. Your own data will differ.
Who can get Cosy Octopus?
Needs a heat pump, electric radiators or an electric boiler.
What are the cheap hours on Cosy Octopus?
Cheap 04:00–07:00, 13:00–16:00 and 22:00–00:00; peak 16:00–19:00. Times are UK clock time, as published by Octopus in October 2026.
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