Octopus Cosy Tariff for Heat Pump Owners: The Complete Guide
Octopus Cosy is the UK's most popular dedicated heat pump electricity tariff, and for good reason. It offers nine hours of cheap electricity spread across three daily windows, perfectly timed for heating your home and hot water at a fraction of the standard rate. But is it right for you, and how much will you actually save?
This guide covers everything you need to know about Cosy Octopus: how it works, current rates, eligibility, and how to squeeze the maximum savings from it.
How Octopus Cosy Works
Unlike a standard electricity tariff where you pay the same rate all day, Cosy divides the day into three rate tiers:
Off-Peak Windows (Cheapest Rate)
- 4:00am to 7:00am — Morning pre-heat window
- 1:00pm to 4:00pm — Afternoon boost window
- 10:00pm to 12:00am — Evening hot water window
Total: 9 hours of cheap electricity per day at approximately 10p per kWh.
Peak Window (Most Expensive Rate)
- 4:00pm to 7:00pm — Evening peak
Total: 3 hours at approximately 30-35p per kWh.
Standard Rate (Everything Else)
- 7:00am to 1:00pm and 7:00pm to 10:00pm and 12:00am to 4:00am
Total: 12 hours at approximately 22-24p per kWh.
The rates vary slightly by region (Octopus operates different pricing zones across GB), so check the exact rates for your postcode on the Octopus website. The figures above are indicative for early 2026.
Current Cosy Octopus Rates (Q1 2026)
Rates as of March 2026 (South England region — other regions vary slightly):
- Off-peak: 10.0p per kWh
- Standard: 23.5p per kWh
- Peak: 33.0p per kWh
- Standing charge: 53p per day
These rates are variable and Octopus can adjust them, typically in line with Ofgem price cap changes each quarter. The off-peak rate has remained consistently below 12p/kWh since the tariff launched, which is roughly 60% cheaper than the standard rate.
Who Is Eligible for Cosy Octopus?
You need to meet three requirements:
- A heat pump: Air source, ground source, or hybrid heat pump. You will need to provide evidence of your installation — typically your MCS certificate or heat pump serial number
- A smart meter: SMETS2 preferred, but upgraded SMETS1 meters work too. If you do not have one, Octopus will arrange a free installation
- An Octopus Energy account: You need to be an Octopus electricity customer. If you are with another supplier, you will switch to Octopus first
The tariff covers your entire household electricity supply — not just the heat pump. This means all your appliances, lighting, and other electrical use are also billed at the Cosy rates. This is important to understand: if you use the washing machine during peak hours, you pay the peak rate for that too.
How Much Can You Save on Cosy?
Savings depend on two factors: how much electricity your heat pump uses, and how much of that usage you can shift to off-peak windows.
Example 1: Average 3-Bedroom Home
Heat pump usage: 4,000 kWh per year. Other household electricity: 3,000 kWh per year.
On standard flat rate (24.5p/kWh):
- Total annual cost: 7,000 kWh × 24.5p = £1,715 + standing charge (£193) = £1,908
On Cosy (60% of heat pump usage shifted to off-peak):
- Heat pump off-peak: 2,400 kWh × 10p = £240
- Heat pump standard: 1,200 kWh × 23.5p = £282
- Heat pump peak: 400 kWh × 33p = £132
- Other usage (assumed 40% off-peak, 15% peak, 45% standard): £564
- Total: £1,218 + standing charge (£193) = £1,411
- Annual saving: £497
Example 2: Larger 4-Bedroom Detached
Heat pump usage: 6,000 kWh per year. Other household electricity: 4,000 kWh per year.
On standard flat rate: £2,450 + £193 = £2,643
On Cosy (65% of heat pump usage shifted to off-peak): Approximately £1,820 + £193 = £2,013
Annual saving: £630
These are realistic figures, not best-case scenarios. Homeowners with excellent insulation who aggressively schedule their heating report savings of £600-800 per year.
How to Maximise Savings on Cosy
Schedule Your Heat Pump Properly
The single most important thing you can do is align your heat pump schedule with the off-peak windows. Here is the optimal approach:
Morning pre-heat (4am-7am off-peak): Set your heat pump to raise the house temperature to your preferred level by 7am. The house then coasts on stored heat through the morning. In a reasonably insulated home, the temperature will drop by only 1-2°C over the next six hours.
Afternoon boost (1pm-4pm off-peak): Your heat pump tops up the temperature during the second cheap window. This is particularly valuable in winter when the morning's stored heat starts to run out.
Avoid the peak (4pm-7pm): Try to avoid running the heat pump during this window. If you have pre-heated effectively during the afternoon off-peak period, the house should hold its temperature for three hours. Some owners set their thermostat 1°C lower during peak to prevent the heat pump kicking in.
Hot water (10pm-midnight off-peak): Schedule your hot water cylinder reheat during this window. A well-insulated cylinder heated to 50-55°C overnight will provide hot water all through the following day.
Improve Your Insulation
The better your home holds heat, the less you need to run your heat pump during expensive periods. Even relatively cheap improvements make a difference:
- Loft insulation top-up: £300-400, reduces heat loss significantly
- Draught-proofing: £100-200, stops warm air escaping through gaps
- Cylinder jacket: £15-25, keeps hot water hotter for longer
- Heavy curtains: £200-500, reduce heat loss through windows overnight
These investments pay for themselves within a year through reduced heat pump runtime and better use of cheap off-peak electricity. See our guide on heat pump insulation requirements for more detail.
Use a Hot Water Cylinder as Thermal Storage
Your hot water cylinder is essentially a thermal battery. On Cosy, the optimal strategy is to heat it during the cheapest window (typically 10pm-midnight or 4am-7am) and avoid reheating it during peak hours.
A 200-litre cylinder heated to 55°C stores approximately 7 kWh of usable energy. That is enough for 2-3 showers and general hot water use. A 300-litre cylinder gives even more buffer. If your current cylinder is small (100-120 litres), upgrading to a larger one is worth considering.
Common Mistakes on Cosy Octopus
Running the Heat Pump on Default Settings
If you do not actively schedule your heat pump around the off-peak windows, you will not save much. The default "weather compensation" or "always on" modes do not account for tariff pricing — they run whenever the house needs heat, regardless of cost.
Ignoring Non-Heat-Pump Usage
Remember, Cosy applies to all your electricity, not just the heat pump. If you run your tumble dryer, oven, or dishwasher during peak hours (4-7pm), you pay 33p/kWh for that too. Try to shift laundry and dishwasher cycles to off-peak windows using delay timers.
Setting Flow Temperatures Too High
A heat pump running at high flow temperatures (above 45°C) is less efficient and uses more electricity. On Cosy, this means more kWh consumed during each window, potentially pushing usage into expensive standard-rate periods. Ensure your flow temperature is optimised — typically 35-40°C for well-designed systems with adequately sized radiators.
Not Monitoring Your Usage
The Octopus app shows your half-hourly consumption and costs. Review it weekly for the first few months to identify patterns. You might discover your heat pump is running during peak hours due to a scheduling error, or that your hot water is reheating at expensive times.
Cosy Octopus and Solar Panels
If you have solar panels, Cosy becomes even more powerful. During spring and summer, your solar panels generate free electricity during the day, meaning you barely draw from the grid at all during standard-rate hours. Combined with cheap off-peak overnight electricity for your heat pump, your annual electricity cost drops dramatically.
Octopus also offers export tariffs (like Outgoing Octopus) for surplus solar generation. This means excess solar energy earns you money whilst your heat pump runs on cheap off-peak electricity. It is an excellent combination.
Switching to Cosy Octopus
The switching process is simple:
- Go to the Octopus Energy website and get a quote for your postcode
- Sign up (or switch from your current supplier — Octopus handles the transfer)
- Once your account is active, request the Cosy tariff through your Octopus account or by contacting their support
- Provide your heat pump details (MCS certificate, make and model, installation date)
- Octopus verifies your heat pump and activates Cosy — usually within a few days
- If you need a smart meter, Octopus arranges a free installation (may take 2-4 weeks)
There is no lock-in and no exit fees. If Cosy does not suit you, switch to another Octopus tariff or leave Octopus entirely at any time.
Is Cosy Octopus Worth It?
For the vast majority of UK heat pump owners, yes. If you can shift even half your heat pump electricity to off-peak windows, you will save £300-500 per year compared to a standard tariff. That is money back in your pocket with no investment required — just a change of tariff and some heating schedule adjustments.
The only scenario where Cosy might not suit you is if your home has very poor insulation and cannot hold heat between off-peak windows. In that case, you might end up running the heat pump during expensive peak hours regardless of your schedule, negating the savings. Address insulation first, then switch to Cosy.
For a broader comparison of all UK heat pump tariffs, see our best heat pump tariff guide and our detailed tariff comparison table.
Frequently Asked Questions
Can I use Cosy Octopus with a ground source heat pump?
Yes, Cosy is available for all heat pump types including air source, ground source, and hybrid systems. The scheduling principles are identical — align your heat pump's operation with the off-peak windows to maximise savings.
Do I need to be home during off-peak windows for Cosy to work?
No. Your heat pump operates automatically based on the schedule you set. The house heats up during off-peak windows whether you are home, asleep, or at work. That is the beauty of pre-heating — the warmth is waiting for you.
What happens during a power cut or smart meter outage?
If your smart meter stops communicating, Octopus bills you on estimated usage until the issue is resolved. They typically use your historical usage pattern to estimate fairly. Contact them promptly if your meter has issues to avoid surprises.
Is Cosy Octopus cheaper than Economy 7?
Almost always, yes. Cosy offers more off-peak hours (9 vs 7), multiple windows throughout the day (vs just overnight), and a lower premium on the daytime rate. Economy 7's daytime rate is typically 28-32p/kWh, whereas Cosy's standard rate is around 23.5p. For heat pump owners, Cosy is the better choice.
Can I run my heat pump continuously on Cosy?
You can, but you will not maximise your savings. Running continuously means the heat pump operates during peak and standard-rate periods as well as off-peak. For best results, schedule intensive heating during off-peak windows and let the house coast during expensive periods. See our guide on time-of-use tariffs for scheduling strategies.
How long does it take to switch to Cosy?
If you are already an Octopus customer with a smart meter, switching to Cosy takes a few days. If you are coming from another supplier, the switch takes 2-3 weeks. If you also need a smart meter installed, allow 4-6 weeks in total.