Tariffs and grants / Supplier-specific tariffs / Cosy Octopus and Intelligent Flux

T-028·Tariffs and grants / Supplier-specific tariffs

Cosy Octopus and Intelligent Flux

Heat pump and battery tariffs using managed operation and peak windows.

Tariff availability, rates and terms were checked on 22 July 2026. They are a dated snapshot, so confirm the address-specific quote before acting.

Cosy Octopus and Intelligent Octopus Flux are two of Octopus Energy’s smart tariffs, built for different equipment. Cosy is open to eligible homes with a heat pump, electric boiler or electric radiators. Intelligent Flux is a combined import and export tariff for homes with solar panels and a compatible battery, where Octopus takes over the battery’s charging and discharging. Intelligent Flux was temporarily unavailable to new customers at this review; Cosy remained open, with Octopus offering fixed rates only during the current period of volatile pricing. Both use a 16:00 to 19:00 peak, and both can change their rates over time.

Cosy Octopus rates and cheap windows

Cosy charges three different rates through the day. The cheap rate, which Octopus calls Cosy Hours, runs in three windows: 04:00 to 07:00, 13:00 to 16:00 and 22:00 to midnight, eight hours in total, priced 51 per cent below the day rate. The peak rate runs 16:00 to 19:00 at 50 per cent above the day rate. Every other hour is charged at the day rate, which sits slightly above Octopus’s standard variable rate.

The rates are set as percentages of the regional flexible tariff, so they differ across the 14 UK distribution regions and shift each quarter with Ofgem’s price cap. In mid-2026 the cheap rate has been reported in the region of 13 to 15p per kWh and the peak rate between roughly 39 and 52p per kWh, depending on region. Cosy comes in a variable version and a fixed version, and neither has exit fees.

Why Cosy uses three cheap windows

Heat pumps run most efficiently little and often rather than in short hot bursts, so the three windows are spaced to keep the heating off the peak. The overnight window preheats the house, the early-afternoon window tops it up and the late-evening window gives a buffer before the next day. Octopus added the 22:00 to midnight window in July 2024, which made the tariff more useful for evening heating.

The Cosy Hours stay on UK local time all year and do not move with the clocks. An in-home display may show the wrong window times, but billing follows the correct local time.

What Cosy saves, and why estimates vary

How much Cosy saves depends heavily on the comparison being made, and published estimates vary widely. Octopus’s own figure is around £82 a year against its OctopusFixed tariff, based on a home using 5,877 kWh in total with 3,177 kWh for heating. Sunsave puts the typical saving nearer £35 a year for a home with a 6,600 kWh heat pump. Energy Stats UK and Cucumber Eco estimate £200 or more a year once the household actively shifts heating into the cheap windows. The gap between these numbers comes from different baselines, whether a fixed tariff, the standard variable tariff or a gas boiler, and different assumptions about how much load moves off-peak. A household that can genuinely run most of its heating during the eight cheap hours saves the most; one that cannot saves far less.

Octopus’s live dashboard for its Cosy heat pump customers reports that 95 per cent of them heat their homes more cheaply than a gas boiler would at April 2026 rates, saving an average of £223 a year against gas. It also reports that 52.2 per cent would still beat a gas boiler on the standard Flexible Octopus tariff rather than Cosy.

Cosy eligibility and metering

Cosy is open to any Octopus Energy customer with a heat pump (air source or ground source), an electric boiler or electric radiators installed and working. The heating does not have to have been installed by Octopus, though Octopus may check that the installer holds MCS accreditation. The property needs a second-generation smart meter (SMETS2) or a Secure-branded first-generation meter (SMETS1) providing half-hourly readings; connecting a new smart meter usually takes about 14 days. The September 2025 terms (version 1.3) state that eligibility requires a heat pump or compatible low-carbon heating system installed and operational.

Cosy is electricity-only. There is no gas version, and the tariff exists to take advantage of how wholesale electricity prices move through the day.

Fixed and variable Cosy

The variable version is the default for new sign-ups, and its rates move each quarter with the price cap. The fixed version keeps the same three-rate structure but locks the rates in at sign-up for the term, typically 12 months for Octopus fixed tariffs, then rolls onto the variable version at term end unless the customer switches. Energy Stats UK tracks a fixed Cosy product (COSY-F) that was updated on 26 June 2026. With a 13 per cent price cap rise due in July 2026, the fixed version is comparatively attractive for anyone wanting price certainty, while the variable version benefits if wholesale prices fall.

Running Cosy with a battery

A home battery can charge during Cosy’s cheaper periods and discharge through the higher-priced period, but the tariff windows do not determine the right battery size. Capacity should be based on the home’s half-hourly winter demand, the energy that must be shifted, the backup reserve and conversion losses. Charge and discharge power must also be sufficient for the relevant windows and loads.

Using several charging periods can increase battery throughput. The financial calculation should therefore include round-trip losses and the exact product warranty’s treatment of cycling and third-party control, not just the difference between the tariff rates.

Adding export: Cosy with Outgoing Octopus

Cosy only covers imports. A home with solar panels that wants paying for export must add a separate export tariff, normally Outgoing Octopus or its half-hourly variant Agile Outgoing. Outgoing Octopus pays a flat 12p per kWh at any time of day, cut from 15p on 1 March 2026, its first change since September 2022. Agile Outgoing pays a half-hourly rate that averaged around 9.4p per kWh over the year to March 2026. The import and export tariffs are billed separately and netted on the monthly statement, and the export side carries no standing charge. Because Outgoing pays the same rate all day, a Cosy plus Outgoing home earns nothing extra for exporting during the evening peak, unlike Flux, which pays its highest rate then.

Signing up for Outgoing needs an MCS or Flexi-Orb certificate for the solar installation, DNO notification confirmation and a separate export MPAN, which together take from a couple of days to a few weeks. A home still receiving Feed-in Tariff export payments has to give those up first.

Intelligent Octopus Flux and matched rates

Intelligent Flux is a combined import and export tariff for homes with solar panels and a compatible battery, where Octopus manages the battery. Import and export rates match: at any moment, the price paid to import a unit equals the price received for exporting one. Rates are lowest off-peak, around 10 per cent below the standard variable rate, and highest during the 16:00 to 19:00 peak, where export has been reported in the region of 30 to 32p per kWh in mid-2026. The rates are variable and regional.

Octopus’s headline claim is up to £300 profit a year. It says that between June 2024 and May 2025, 34 per cent of Intelligent Flux customers paid less to import than they earned from export, and the top 12 per cent covered their whole bill plus more than £314. Sunsave estimates average earnings of around £893 a year for a 4.9 kWp system with a 5.2 kWh battery exporting 65 per cent of its generation. Actual earnings depend heavily on the size of the system and how much the home exports.

How Octopus controls the battery on Intelligent Flux

On Intelligent Flux, Octopus controls the battery’s charging and discharging rather than the owner. It charges the battery from the cheapest and greenest periods overnight and through the day, using weather forecasts to predict solar generation, then discharges into the 16:00 to 19:00 peak. The owner cannot set a target charge level or a ready-by time, unlike Intelligent Octopus Go. The battery holds a minimum 20 per cent state of charge. Only one device can be enrolled per property, so a home with both a compatible battery and a compatible EV charger has to choose which one Octopus controls.

Octopus holds exclusive rights to use the battery for demand response while the home is on the tariff, so it cannot also join another virtual power plant or flexibility scheme. Disconnecting the battery from Octopus’s control for more than 30 days loses eligibility.

Owner reports are mixed. Some find the automation works as they expect, particularly in summer. Others report the battery being scheduled to charge during the peak, being left idle or using only part of its capacity, and some have moved to standard Flux to schedule the battery themselves.

When Intelligent Flux pays and when it does not

The peak export rate near 32p per kWh looks generous, but importing during that same peak costs the same 32p. The tariff works for a home that exports more over the year than it imports; for a home that imports more than it exports, the matching works against it. One analysis illustrates this: a home importing 4,900 kWh and exporting 3,500 kWh a year at matched rates around 21p would pay roughly £295 net, while the same home importing on Intelligent Octopus Go (around 8p) and exporting on Outgoing (12p) would finish about £28 in credit.

Intelligent Flux tends to suit a home with a large solar array, a large usable battery, a generous export limit, a three-phase supply that allows higher export power and low daytime and winter import. It tends not to suit a home with heavy evening use, EV charging or a heat pump, a small battery or a modest array.

Intelligent Flux eligibility and compatible batteries

Intelligent Flux needs solar panels, a compatible battery connected to Octopus over an application programming interface (API), a SMETS2 or Secure SMETS1 meter and the home already on both an Octopus import tariff and an Octopus export tariff. It also needs a supported phone: an iPhone on iOS 15 or later, or Android 7 or later. The solar installation needs an MCS or Flexi-Orb certificate and DNO notification, as standard Flux does.

Octopus’s public eligibility picker lists ten brands: AlphaESS, Ecoflow, Enphase, Fox ESS, GivEnergy, Hanchu ESS, Huawei, Sigenergy, SolarEdge and SunPower. Its own FAQ describes only four as currently integrated: GivEnergy, Enphase, SolarEdge and Tesla Powerwall, with Hanchu ESS coming soon. The two lists do not match, and the eligibility check inside an Octopus account is the reliable one. Solis and LuxPowerTek do not appear on any public list as of mid-2026.

Both Flux tariffs are paused to new customers

Octopus paused standard Flux and Intelligent Flux on or around 5 March 2026, along with Snug Octopus, and as of July 2026 has not given a reopening date. The notice on both pages reads: “Energy prices are particularly volatile right now, so this tariff is temporarily unavailable.” The matched-rate design leaves Octopus more exposed when wholesale prices swing, because the rate it pays for export is tied to the rate it charges for import.

Existing Flux customers keep their tariff and are unaffected. Anyone who leaves Flux cannot rejoin while the pause holds, and a separate 30-day rule blocks rejoining any smart tariff for 30 days after switching away. The previous Flux pause, in 2022 to 2023, lasted several months.

Choosing between Cosy, Flux and Go

Octopus’s own guidance maps equipment to tariffs: a heat pump points to Cosy, solar plus a battery to Flux, a battery without solar to Agile plus Outgoing and a heat pump plus EV to Intelligent Octopus Go. A heat pump with solar is steered to Cosy paired with Outgoing.

Some owners with a heat pump, solar and a battery run Cosy through winter, when heating demand is high and generation is low, then switch to Intelligent Flux in summer, when export earns more. That seasonal switch is harder to run now that Flux is closed to new sign-ups, and the 30-day re-switch rule limits how quickly a household can move between smart tariffs. For a home with solar, a battery and an EV, whether Intelligent Flux or Intelligent Octopus Go comes out ahead turns mainly on the ratio of generation to consumption. A home generating well above what it uses gains more from Flux’s summer export, while Go’s cheap overnight import wins for a home that imports more than it exports.

Heat pump tariffs from other suppliers

Cosy is not the only heat pump tariff. Several other suppliers run heat pump time-of-use tariffs, all import-only, so each needs a separate export tariff for a home with solar, usually a SEG (Smart Export Guarantee) rate.

Supplier Tariff Off-peak window Off-peak rate
ScottishPower Heat Pump Saver 11:00 to 16:00 14p per kWh
EDF Heat Pump Tracker 04:00 to 07:00 and 13:00 to 16:00 10p below the regional standard rate
E.ON Next Next Pumped 06:00 to 16:00 below the standard rate, with a 16:00 to 19:00 peak above it
British Gas Heat Pump tariff 00:00 to 07:00 and 13:00 to 16:00 half-price electricity

Cosy’s eight cheap hours are split across three windows, and it adds a 16:00 to 19:00 peak above the day rate. E.ON Next Pumped has the longest single off-peak block at ten hours but also charges a peak. British Gas gives ten half-price hours across two windows with no late-evening dip. EDF’s Heat Pump Tracker uses the same two daytime windows as Cosy but without the 22:00 to midnight one. OVO’s Heat Pump Plus tariff has been discontinued.

Feed-in Tariff, SEG and export tax

A home still on the old Feed-in Tariff (FiT) is paid two ways: a generation element for everything generated and an export element for what leaves the property. Switching to a smart tariff never affects the generation payment, which continues. Because Cosy is import-only, a Cosy customer can keep FiT export payments untouched. Adding Outgoing Octopus, or moving to Flux, means giving up the FiT export element, and that decision cannot be reversed. The trade is usually worth it, because Flux’s peak export around 30p or Outgoing’s flat 12p beats a typical FiT deemed export rate of about 5 to 6p, though it depends on how much the home exports and how generous the old FiT rate is. A home on a SEG tariff rather than FiT can switch freely, with no export element to surrender.

Export earnings are usually tax-free, but not automatically. HM Revenue and Customs (HMRC) treats domestic microgeneration income as exempt from Income Tax where the electricity is generated mainly for the home’s own use and export is incidental, under a specific exemption (section 782A of the Income Tax (Trading and Other Income) Act 2005). HMRC guidance reads this as covering homes that generate no more than about 20 per cent above their own consumption, though that is HMRC’s interpretation rather than statute. A separate £1,000 trading allowance covers miscellaneous income including export earnings, so a household earning under £1,000 a year from export has nothing to declare. Most Cosy plus Outgoing homes earn well below that; Intelligent Flux homes with high export can approach £1,000 but usually stay under it. A home that does exceed £1,000 without the domestic exemption may need to file a Self Assessment return by 31 January, with a £100 penalty for filing late. An estimated 54,000 solar households were thought to need returns for 2024-25.

Applies to

Solar, Battery, Heat

Last reviewed

22 Jul 2026