How Octopus Cosy works
Octopus Cosy gives you six hours of cheap electricity every day, split across three two-hour windows. The windows are fixed: they do not change day to day, do not require you to check prices, and do not vary by season. You know in advance exactly when your cheap electricity arrives.
The three windows are approximately 04:00-06:00 in the early morning, 13:00-16:00 in the early afternoon, and 21:00-23:00 in the evening. During these windows, the Cosy cheap rate sits at approximately 12-15p per kilowatt hour. Outside these windows, you pay a standard rate of approximately 24-26p.
The tariff was designed with heat pumps in mind. Heat pumps run most efficiently when they run for long, consistent periods rather than short bursts. The Cosy windows, particularly the afternoon period, align with times when heat pump operation is both cheap and beneficial. The afternoon window specifically aligns with peak solar generation, meaning grid electricity is typically abundant and inexpensive when Cosy prices are low.
Cosy requires a SMETS2 smart meter. The switch is done through Octopus Energy's website and takes effect within the standard switching timeline.
The three cheap periods and their practical uses
Each of Cosy's three windows serves a different household purpose, and understanding which loads to assign to each period is where the tariff pays off.
The early morning window, approximately 04:00-06:00, suits water heating and any overnight appliance runs that completed during the night but might benefit from topping up. If you have an immersion heater or hot water cylinder, setting it to boost in this window means you enter the morning with a full hot water tank at cheap rates.
The afternoon window, approximately 13:00-16:00, is the most flexible. This is when solar generation peaks in spring and summer, reducing grid costs and producing the most value. Running your dishwasher, washing machine, or tumble dryer in this window captures cheap electricity while contributing to grid balance. Heat pump owners who want to pre-warm the home before the evening can do so in this window at a significantly lower cost than waiting until the evening standard rate applies.
The evening window, approximately 21:00-23:00, is the final opportunity before midnight. Running any remaining appliances here before bed, topping up water heating, and setting overnight timers all fall naturally into this period. It also sits after the traditional 5-8pm peak, when grid prices are high and both Agile and standard tariffs are expensive.
Cosy vs Agile: when Cosy wins
Cosy beats Agile in one clear context: households that want reliable cheap electricity at known times without any daily management.
Heat pump owners are the primary beneficiary. A heat pump running during Cosy's afternoon window benefits from cheap rates, solar grid surplus, and optimal ambient temperature conditions for heat pump efficiency. The combination produces excellent economics without requiring the homeowner to track prices daily.
Households with rigid routines that happen to align with Cosy's windows also benefit significantly. If your dishwasher always runs after lunch, your washing machine always runs in the early afternoon, and you always use your tumble dryer before bed, Cosy maps almost perfectly onto your existing behaviour. You save money without changing anything.
The psychological argument for Cosy is genuine. Agile's daily price variation, while financially rewarding, creates a form of engagement that some households find stressful rather than satisfying. Knowing that cheap electricity arrives at consistent times every day, without checking any dashboard, has real value. Lower bill anxiety is itself a benefit that should be counted alongside the financial numbers.
Cosy vs Agile: when Agile wins
Agile consistently beats Cosy for households willing to engage with daily price information.
Agile's overnight rates, typically 2-8p between midnight and 6am, are significantly below Cosy's cheap rate of 12-15p. For households that run dishwashers, washing machines, and EV charging overnight, this gap represents material savings. A 10kWh overnight load costs £1.20 at Agile's average 12p overnight rate and £0.40 at a 4p Agile overnight rate. At Cosy's 12-15p, the same load costs £1.20-1.50. The overnight advantage is substantial for high overnight users.
Agile's plunge pricing events have no equivalent on Cosy. When the wholesale market drives Agile prices negative, 5-10 times per month, you earn money for consuming electricity. Running every available appliance during a negative-price event turns your energy bill into a source of income for that half-hour. Cosy customers pay 12-15p during the same period.
EV owners with flexible charging schedules consistently achieve lower per-charge costs on Agile than on Cosy. The gap between Agile's average overnight rate and Cosy's cheap rate represents approximately £30-50 per year for a household driving 8,000-10,000 miles annually. On the best Agile nights, the saving against Cosy is considerably larger. See the live dashboard on any weeknight to observe the difference between current Agile rates and Cosy's 12-15p benchmark.
Who Cosy is best for
Octopus Cosy has a clear target household, and it suits that household extremely well.
Heat pump owners are the primary audience. The design of the tariff, specifically the afternoon window, was built around heat pump usage patterns. If you have a heat pump and want to run it cheaply without daily price management, Cosy delivers this better than any other Octopus tariff except Agile for highly engaged users.
Older households and those managing on fixed incomes often find Cosy's predictability genuinely valuable. Knowing that cheap electricity arrives at the same three times every day removes the cognitive load of energy management. For households where simplicity matters more than maximum optimisation, Cosy is the right answer.
Any household whose natural daily rhythm aligns with the three Cosy windows should consider this tariff carefully. If you already run most of your appliances in the early afternoon and evening, Cosy rewards you for doing what you already do. The switch is low-effort and the saving is immediate.
How to switch to Cosy
Switching to Octopus Cosy follows the same process as any Octopus tariff change. You need a SMETS2 smart meter. If you already have one, the tariff change is handled through your Octopus account and takes effect within your current billing period, typically within a few days.
If you are switching from another supplier, the full switching process takes approximately 17 days. Octopus manages the meter and tariff setup. There are no exit fees to leave Cosy and no lock-in period. If you later decide Agile suits you better, switching between Octopus tariffs is free and fast.
Many households use Cosy as a stepping stone to Agile. They switch to Cosy first, learn to shift loads to the cheap windows, and then move to Agile once they are comfortable with the concept and ready to engage with daily price information for additional savings.