Octopus Cosy — The Heat Pump Tariff Reviewed
Cosy is built around a heat pump's daily rhythm. Two cheap windows — 4am–7am and 1pm–4pm — let you pre-heat the house when prices are low, then coast through the expensive 4pm–7pm peak with stored warmth. Done well, it's the cheapest way to run a heat pump in the UK.
In one sentence
Heat pump tariff with two off-peak windows. Cheapest UK option for low-flow-temp heating. Peak rate stings if you can't avoid 4pm–7pm.
What Octopus Cosy actually is
Octopus Cosy is a three-rate (time-of-use) electricity tariff with two cheap windows — 04:00 to 07:00 and 13:00 to 16:00 — and a high-cost peak from 16:00 to 19:00 every day.
It's designed to match how an efficient heat pump should run: pre-heat early morning while the cylinder warms, top up mid-afternoon before the peak, then ride out the expensive evening window on stored heat in the fabric and water.
Eligibility: you need a heat pump, a SMETS2 smart meter, and Octopus needs to verify the install. Customers without a heat pump are usually declined or pushed to Go/Agile.
Pros
- Two cheap windows totalling 6 hours per day — much more usable than Go's single 5-hour overnight window.
- Off-peak rate of ~13p/kWh is roughly half the price cap.
- Mid-afternoon window lines up perfectly with solar PV gaps in winter.
- Genuinely the cheapest tariff for running a UK heat pump if you have the controls.
- No exit fees.
Cons
- Peak rate of ~36p/kWh (4pm–7pm) is well above the cap — you must avoid using power then.
- Requires a heat pump — Octopus verifies before approving.
- Manual heating controls don't really work — you need a smart controller or you'll forget.
- Cooking dinner in the peak window costs 30–40% more than on the standard variable.
- Day rate (everything outside the three windows) is also higher than the cap.
Who Octopus Cosy suits
- Heat pump owners with a well-insulated home and a heat curve set up for low-flow-temp running.
- Households with a hot water cylinder that can be reheated in the off-peak windows.
- Anyone with thermal mass (solid floors, brick walls) that holds heat through the 3-hour peak.
- Smart heating controllers (Homely, Havenwise, Adia) that schedule based on Cosy rates.
Who should avoid it
- Homes without a heat pump — you can't sign up.
- Poorly insulated homes that lose heat fast through the peak window.
- Households that need a hot dinner cooked on the hob at 6pm every night and can't shift it.
- People not willing to set up a heating schedule — running 24/7 on Cosy is more expensive than the standard variable.
Current rates
Live rates pulled from the Octopus Energy public API for Octopus Cosy (COSY-FIX-12M-26-06-25). Standing charges and unit rates shown include VAT. Agile shows a 24h average; half-hourly prices vary throughout the day.
| Region | Unit rate | Standing charge |
|---|---|---|
| London | 33.37p/kWh | 44.12p/day |
| South East | 30.81p/kWh | 49.41p/day |
| North West | 30.53p/kWh | 46.63p/day |
| Scotland | 33.40p/kWh | 57.99p/day |
| Wales (South) | 30.34p/kWh | 56.56p/day |
Worked example: heat pump home, 6,000 kWh electricity/year
A 3-bed heat-pumped home uses 6,000 kWh/year (4,000 kWh for heating, 2,000 kWh other). On the Ofgem cap that's £1,620 in unit charges.
On Cosy with smart controls: 3,000 kWh in the off-peak windows at 13p (£390), 2,500 kWh during the day at 26p (£650), and just 500 kWh during the peak at 36p (£180). Total: £1,220 — a £400 saving.
On Cosy without smart controls (heat pump runs 24/7, cooking in the peak window): bill rises to £1,720, which is £100 more than the cap. The savings only materialise if heating is scheduled to avoid 4pm–7pm.
How to switch to Octopus Cosy
- Confirm you have a heat pump installed (Octopus will ask for make/model during signup).
- Confirm your SMETS2 smart meter is sending half-hourly readings.
- Apply at octopus.energy/cosy — Octopus may take 1–2 weeks to verify the heat pump install.
- Set up smart heating controls (Homely, Havenwise, or any controller that supports Cosy windows). Without these, savings are marginal.
- Schedule hot water reheats for the off-peak windows. Don't run an immersion in the peak.
- After 30 days, compare bills against the price cap. If you're not at least 15% under, your schedule needs work.
Independent review. Power Guardian UK is not affiliated with Octopus Energy. Rates shown are indicative for Octopus Energy's Octopus Cosy tariff at the time of review — check the supplier's website for current pricing before signing up.
Frequently Asked Questions
Other Octopus tariffs
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Single daily rate for gas and electricity. Cheaper than the cap most of the year, painful during winter wholesale spikes.
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