Octopus Flux with solar How it works, best settings and is it worth switching?
Octopus Flux charges you cheaply between 02:00 and 05:00, and pays a high rate for electricity you export between 16:00 and 19:00. Paired with solar and battery storage, this three-period tariff is one of the most financially attractive products in the UK market. This guide covers how Flux works, how to configure every major inverter brand, and what can go wrong.
If you're dealing with a fault related to this topic, a remote diagnostic identifies the root cause and recommends the fix — usually within 30 minutes. All major brands supported.
Book a diagnostic — £75 → How diagnostics workThe three-period Flux day explained
Unlike flat-rate tariffs, Flux charges different prices for electricity at different times of day — and, uniquely among simple consumer tariffs, it also pays a meaningful rate when you export during peak hours. Understanding the three periods is the foundation of everything else.
Cheapest import rate of the day. This is when you charge your battery from the grid. Import during this window only — avoid charging at any other time if you can help it.
Standard Flux rate — higher than the off-peak rate but lower than the peak rate. Solar generation and battery discharge cover household demand during this period to minimise expensive imports.
Most expensive import. But Octopus also pays a high export rate during peak — exporting stored battery energy during this window is where most of the financial benefit comes from.
Octopus Go has one cheap import window (usually 00:30–04:30) and a flat standard rate for everything else. Export earnings are based on the standard SEG rate, which is not tariff-specific. Flux adds a third element: a premium export rate during the peak window. This means Flux rewards both the import side (cheap charging) and the export side (selling at peak) — Go only rewards the import side. The tradeoff is that Flux's standard rate is typically higher than Go's daytime rate, so your bill balance depends heavily on how much you can shift to the off-peak and peak windows.
Flux has three eligibility requirements: a SMETS2 smart meter (second-generation, capable of half-hourly reads); an inverter capable of bidirectional metering (both import and export must be recorded by your smart meter); and an active export setup (your inverter must be permitted to export — export limit not set to zero). If any of these are missing, contact Octopus before switching — they can arrange a meter upgrade if needed.
You do not need a battery to be eligible for Flux, but without a battery you cannot take advantage of the cheap overnight rate or build up stored energy for the peak export window. A solar-only Flux customer only benefits from the peak export rate when panels are still generating after 16:00 — which is limited in autumn and winter.
When you are on Octopus Flux, your export earnings during the peak window are handled directly through the Flux tariff — Octopus pays you the peak export rate for units exported between 16:00 and 19:00, and a lower rate outside that window. This replaces a separate SEG contract in most cases. If you have an existing SEG contract with a different supplier, check whether that contract requires you to use Octopus as your import supplier too, or whether you can hold both simultaneously. Most SEG contracts require your import and export to be with the same supplier for simplicity. See the Smart Export Guarantee guide for details on how SEG and Flux interact.
Is Octopus Flux worth it with solar?
The answer depends almost entirely on your battery capacity and how you use it. Here are the three scenarios, from worst to best.
A solar-only household on Flux benefits from the peak export rate when panels are still generating after 16:00 — mainly in summer. In winter, panels rarely produce meaningful output after 15:00 and the peak window yields little export. Meanwhile, the higher standard Flux rate applies for all evening and overnight import. Unless you have a very large east/west-facing array that generates well in the late afternoon, Flux is not compelling for solar-only homes. Octopus Go or a standard fixed-rate tariff with a competitive SEG rate is usually a better fit.
A 5 kWh battery can typically charge fully in the 3-hour off-peak window and discharge meaningfully during the 3-hour peak export window. In winter, the battery is likely to reach 100% from the cheap grid charge alone. In summer, solar may fill the battery before 16:00 without any overnight grid charge, leaving the cheap window available for future use. The limiting factor is battery size: a 5 kWh battery exported at a high peak rate generates less income per day than a larger system. Flux is generally worth it with a small battery — just not transformative.
This is the scenario Flux is designed for. A 10 kWh battery charges fully from the grid during the off-peak window. Solar tops it up again during the day at zero cost. The battery then has a full or near-full charge available to export during the peak window. In winter, the cheap overnight charge plus peak export can effectively give you a daily net energy cost close to zero or even positive — the peak export income offsets the overnight charge cost. In summer, solar generation often means no overnight grid charge is needed at all, making the peak export window essentially pure income. A 10 kWh+ system well-configured for Flux is one of the best financial propositions in consumer solar energy.
The optimal daily Flux strategy for solar + battery
A well-configured Flux setup follows the same daily cycle in winter. Summer shifts the solar contribution forward, often eliminating the need for any grid charge at all on sunny days.
The inverter draws power from the grid and charges the battery to 100% SoC. Cost: approximately 21–27p (3 hours × ~7–9p/kWh × 3 kW typical charge rate), less if the battery was already partially charged from the previous day's solar. This is the only time grid import is financially acceptable on Flux.
Solar panels generate from sunrise. The inverter prioritises powering the house directly from solar, then re-charges the battery if it was partially discharged, then exports any remaining surplus. During this period, the aim is to keep the battery at a high SoC so it has maximum charge available for the 16:00 peak export window.
In summer, this period may fully recharge the battery without any grid input, making the overnight cheap charge unnecessary. In winter, solar production is lower and the battery likely relies on the overnight grid charge to reach full capacity.
The inverter discharges the battery to the grid (Timed Export mode) at maximum rate during the three-hour peak window. A 10 kWh battery at 3.6 kW export rate can push approximately 10.8 kWh to the grid during this window (subject to your export limit). At a ~30p/kWh export rate, this generates approximately £3.24 per day — around £1,180 per year before accounting for the overnight charging cost.
After the peak export window closes, the battery switches to powering the house (Timed Discharge or Eco Mode) to cover household demand through the evening. The aim is to avoid paying the standard Flux rate for any avoidable evening imports. Set a minimum SoC reserve of 5–10% to ensure there is always some charge remaining when the off-peak window opens at 02:00. An empty battery at 02:00 charges more slowly and may not reach 100% by 05:00.
A remote diagnostic session reviews your portal data and schedule settings to confirm whether your charge and export windows are aligned to the Flux periods — and identifies any configuration issues costing you income.
How to configure your inverter for Octopus Flux
The settings are the same across all brands in principle — a charge window from 02:00 to 05:00 and an export window from 16:00 to 19:00 — but the interface, terminology, and mode names differ. Here is what to do for each common UK inverter.
All four brands use SolarMan or a similar TOU schedule interface. The principle is identical: a charge window 02:00–05:00 (grid charge, SoC target 100%) and a discharge-to-grid window 16:00–19:00 (minimum SoC 5–10%). The key variable between brands is whether grid export is available on your firmware version and whether the brand's portal labels the mode as 'Sell', 'Export', 'Discharge to Grid', or 'Force Discharge'.
Octopus API integration vs manual schedule configuration
Octopus offers API connections to compatible inverters that automate charge and export window management. This is not the same as manual TOU configuration — and running both simultaneously is a common cause of erratic battery behaviour.
You configure TOU slots directly in your inverter portal. No API connection. You control exactly when the battery charges and exports. Settings persist unless you change them or a firmware update resets them. Compatible with all inverter brands.
Octopus connects to your inverter's cloud API and sends automated charge/export signals. Flux uses this integration to manage the three daily periods automatically based on its pricing model.
Why your Flux setup might not be working correctly
These are the five most common reasons a Flux-configured system fails to perform as expected — in order of frequency.
Check in order: (1) Is the TOU charge slot correctly configured with grid charge enabled? (2) Is the system mode set to allow grid charging (not 'Self-Use only' which may reject grid charge on some brands)? (3) Is the inverter clock showing the correct current time? If the clock is on GMT in summer (BST), the slot fires one hour late and misses the off-peak window. (4) If you have an Octopus API connection, is it conflicting with the manual schedule? (5) Is the CT clamp correctly oriented — a reversed clamp causes the inverter to misread import as export and refuse to charge from the grid.
See the battery not charging guide for systematic diagnosis steps.
Check in order: (1) Is the export limit set to a non-zero value? If the export limit was reset to 0W (common after firmware updates), no power can reach the grid even in Timed Export mode. (2) Is the TOU export slot correctly configured as 'export to grid' rather than 'discharge to house'? These are different modes — Timed Discharge powers the house from the battery but does not push energy to the grid for export income. (3) Does the battery have sufficient charge at 16:00? If morning solar was poor and the overnight charge was insufficient, the battery may be near its minimum SoC before the export window even opens.
Flux rate periods are defined in GMT (UK standard time) and do not move for British Summer Time. When BST begins at the end of March, if your inverter is configured to follow local time automatically, its TOU windows shift by one hour relative to the Flux periods. The charge window effectively runs 03:00–06:00 BST (partially inside the standard Flux rate period), and the export window runs 17:00–20:00 BST (one hour late, partially missing the peak).
A firmware update to the inverter or battery can reset TOU configuration to factory defaults — deleting or disabling your Flux windows without warning. After any update, immediately check your charge schedule and export slot in the portal to confirm they are still active and correct. This is the most common cause of sudden Flux performance decline that appears without any obvious trigger. See the firmware update risks guide for full details of what to check.
If you are exporting during the peak window (confirmed in your monitoring portal) but your Octopus bill does not reflect the expected peak export rate, the issue is usually one of: (1) your smart meter is not correctly registering the half-hourly export data (contact Octopus to investigate); (2) the inverter export is going through a sub-meter that the smart meter cannot see; or (3) your Flux tariff switch is not yet complete and you are still on the previous tariff. Log into the Octopus app, navigate to 'Usage', and check whether half-hourly export data is visible — if the chart is empty or shows estimated reads, the smart meter communication needs investigating.
Related guides and configuration pages
The foundations of battery storage — charge cycles, SoC, degradation, and how inverters control dispatch.
How SEG works, current rates, and how Flux export income differs from a standard SEG contract.
What export limits are, why they cap your Flux peak export income, and how to check yours.
Firmware updates that reset your Flux charge schedule or export limit without warning — what to check.
GivEnergy-specific tariff setup — Octopus Go, Agile, Intelligent, Flux, Economy 7 charge schedule settings.
Specific Sunsynk TOU configuration issues — clock errors, grid charge settings, and mode conflicts.
Frequently asked questions
Octopus Flux is a time-of-use tariff from Octopus Energy with three daily price periods. Off-peak (02:00–05:00) has a cheap import rate for charging your battery from the grid. The standard Flux rate applies during the rest of the day. Peak (16:00–19:00) has a high import rate but also a high export rate — Octopus pays a meaningful amount for every unit you push back to the grid during those three hours. Requires a SMETS2 smart meter and works best with battery storage.
For solar-plus-battery households, yes — Flux is one of the most financially attractive tariffs available. The combination of cheap overnight charging, solar self-use during the day, and a high export rate at peak makes it particularly effective for systems with 5–10 kWh of battery capacity and 3–6 kW of solar. A 10 kWh battery well-configured for Flux can generate significant daily export income on top of solar savings. The exact benefit depends on current Flux rates, your battery capacity, and how well the schedule is configured.
You do not need a battery to be eligible for Flux — a solar-only system can benefit from the high export rate when panels are still generating after 16:00. However, in winter when panels produce little after 16:00, a solar-only Flux customer receives no peak export benefit and pays the expensive peak import rate for evening electricity. Battery storage is what makes Flux compelling year-round: it stores cheap overnight grid electricity and solar generation, then dispatches it during the peak window regardless of what the panels produce.
Any inverter with a configurable Time of Use (TOU) charge and discharge schedule can be set up for Octopus Flux — this includes GivEnergy, Sunsynk, Solis, Fox ESS, Growatt, SolaX, Sofar, LuxPower, and Hanchu. GivEnergy and SolarEdge support direct Octopus API integration. For all other brands, manual TOU configuration works reliably: a charge slot 02:00–05:00 and an export slot 16:00–19:00.
Octopus Flux windows are defined in GMT and do not shift for British Summer Time (BST). In summer, when clocks move forward one hour, if your inverter is set to local time your TOU windows fire one hour early relative to the actual Flux periods. The fix is either to keep your inverter clock on GMT year-round, or adjust TOU windows seasonally: charge 01:00–04:00 BST (= 02:00–05:00 GMT) and export 15:00–18:00 BST (= 16:00–19:00 GMT). Check your billing data in the first week of each season to verify alignment.
They suit different users. Flux has fixed daily windows — predictable, easy to configure manually, and consistent year-round. Agile has half-hourly variable pricing with potential for very cheap or even negative import rates during periods of high grid generation, and very high export rates on cold still winter evenings. Agile requires home automation (Home Assistant, GivTCP, or similar) to take full advantage of dynamic pricing — manual TOU windows miss most of the cheapest periods. For households with home automation and the time to optimise, Agile often outperforms Flux. For a reliable, well-optimised set-and-forget approach, Flux is usually the stronger choice.
Flux not charging or exporting correctly?
If your battery is not charging during the off-peak window, not exporting at peak, or your Flux income looks lower than expected, a remote diagnostic reviews your schedule settings and portal data to find the cause — usually within 30 minutes.