On a Sunsynk hybrid, Octopus Flux comes down to two clock windows: charge the battery from the grid between 02:00 and 05:00, then let it discharge and export between 16:00 and 19:00. You can set both by hand on the inverter’s own timer today, and that fixed pair is the core of a Flux setup: the cheap overnight charge and the peak discharge you schedule yourself. Sunsynk also has a newer live-price Flux feature in its Connect app that tries to automate the same thing, but Sunsynk still labels it beta, so treat the manual windows as your reliable foundation and the integration as an experiment.
Go straight to the job you have:
- Set the overnight force-charge window
- Set the 16:00 to 19:00 peak export
- Decide whether to use the beta live-price feature
- Do the same on a Deye
The short answer for a Sunsynk on Flux
Set the Sunsynk Work Mode timer to grid-charge the battery from 02:00 to 05:00 towards your chosen state of charge, then allow it to discharge and export during the 16:00 to 19:00 peak. That fixed pair of windows is the part you set by hand, the cheap charge and the peak discharge, and it stays visible on the inverter. Sunsynk’s Connect live-price feature can schedule it for you, but it is beta and blinds your load reading while exporting.
One status check before you start. In March 2026 Octopus closed both standard Flux and Intelligent Octopus Flux to new sign-ups, and at the time of writing in July 2026 they had not reopened. If you are already on Flux you keep it, and this guide is for you. If you are not on it yet you cannot currently switch onto it, so check the live Octopus Flux page for the current status and look at Outgoing Octopus or Agile Outgoing for export in the meantime.
I run a Sunsynk 3.6 ECCO with Fogstar batteries and Solar Assistant, but on Octopus Go rather than Flux. The fixed-window mechanism below is the same timer I use every night. The exact Flux windows and the native Connect integration I have set from Sunsynk’s and Octopus’s own documentation, not from running Flux on my own system, and I say so wherever it matters.
| Flux window | What the Sunsynk should do | Why it matters |
|---|---|---|
| 02:00 to 05:00 super off-peak | Grid charge the battery towards your target state of charge | The cheapest import of the day, so this is when you fill the battery from the grid |
| Daytime standard rate | Run the house from battery and solar, grid charge off | Import sits at the middle rate, so you want to avoid buying then |
| 16:00 to 19:00 peak | Cover the house from the battery first, then export any surplus | Both import and export are at their highest now. Serving the house from storage keeps you off the dear peak import, and the surplus you send out earns Flux’s best export rate of the day |
Set the overnight force-charge window
Grid charging on a Sunsynk is a permission chain, not a single switch. If any link is missing the battery will not charge, and raising a current limit will not fix a missing permission. Work through it in this order for the Flux cheap window.
- Open the Work Mode timer. In Sunsynk Connect it sits under the plant’s System Mode or Work Mode tab; on the inverter’s own screen it is the System Mode Setup timer grid. Set a row that covers 02:00 to 05:00.
- Enable grid charging for that row, so the grid is allowed to fill the battery in the window.
- Set the row state of charge to the level you want to reach overnight, for example a high target on a day you expect little sun.
- Confirm the actual state of charge is below that target, or the row has nothing to do.
- Check that the charge current and the battery’s own BMS allowance can add that much energy inside three hours.
For the overnight target, let the next day’s solar decide. In winter, or before a dull forecast, charge close to full, roughly 90 to 100%, because little solar will arrive to top it up. On a bright spring or summer day a lower target, around 50 to 70%, leaves headroom for free solar to fill the rest so you are not paying to import energy the sun would have given you. The remaining daytime timer rows simply hold grid charge off and let solar and the battery run the house until the peak.
On my own Sunsynk the same timer runs 00:30 to 05:30 towards 90% for the Octopus Go window. For Flux you simply move the window to 02:00 to 05:00 and pick the target that suits the next day. The mechanism is identical; only the clock and the tariff change.
One rule survives every tariff: keep the row target coordinated with the Low Batt and Shutdown protection values, and never lower those protection thresholds just to make a schedule complete. A timer row asking for behaviour below the battery’s protection floor is a setup you will have to unpick later.
Set the 16:00 to 19:00 peak export
The peak window has two jobs, and the order matters. First the house should run off the battery, so you buy almost nothing at the peak import rate, which is the dearest import of the day on Flux. Only then does surplus or scheduled discharge go out for the peak export rate. So the inverter has to be allowed both to cover the load from the battery and to export during 16:00 to 19:00. Two things must be true at once.
- The operating mode permits export. On a Sunsynk that means a selling or export-enabled mode rather than a strict zero-export configuration, set according to your exact interface and grid connection.
- The battery is allowed to discharge in the window. Check that no timer row or automation is holding discharge current near zero across 16:00 to 19:00.
How much actually leaves the house depends on which export behaviour you pick, a ladder from least to most aggressive:
- Zero-export or load-first only: the battery covers the house but nothing is sold. This is the right setting if your install is not approved to export.
- Export-enabled with discharge allowed: the house is served first and genuine surplus spills to the grid.
- Live-price or Selling First scheduled discharge towards an export state of charge: the system actively discharges to sell across the window, still serving house load first, with the CT blind spot covered below.
Whichever you pick, export has to stay inside the G98 or G99 limit your DNO agreed. These are user-level timer and mode settings only. If your install was never approved to export, a selling mode is not a workaround, and you should not raise an export limit or touch grid-code parameters to force energy out.
There is a trap worth naming. To force surplus daytime solar out to the grid on my Go setup, I cap the battery’s Max Charge Current low during the day so the inverter has to export rather than trickle solar into an already-full pack. On Flux the logic often flips: you may want the battery fuller going into the 16:00 peak so there is more stored energy to sell when the rate is highest. Decide whether a given afternoon is a self-use day or an export day before you copy a current cap from a Go guide.
If you do cap charge or discharge current, learn from a mistake I made once: never set either to zero. Solar Assistant and any rule engine can crash or lose power, and the last value written stays on the inverter. A zero left in place after a crash silently blocks charging or discharging for the rest of the day. Leave a small floor, a couple of amps, so a failed automation degrades gently instead of stranding the battery.
The Sunsynk Connect live-price Flux feature is beta
Sunsynk added a live-price Octopus Flux feature inside the Connect portal and app that reads the tariff and schedules import and export for you, rather than you setting the two windows by hand. It is a real feature with an official setup article, but Sunsynk describes it as still in beta for both Octopus and Sunsynk and advises using it at your own risk. That wording is the reason this section sits after the manual method, not before it.
How to turn on the Octopus Flux feature
Sunsynk’s support article documents the path. In the Connect portal or app, open the plant list, select the more menu next to your plant, then Edit. Choose Revenue Info, then Live Price, then set Octopus Flux as the provider. You then set two state-of-charge figures: the Import level the battery charges to from the grid, and the Export level it discharges to when selling. The Import window is preset as Time 1 and the Export window as Time 2, with the start and end times already filled to the best-value periods, so the feature does the clock work that you would otherwise do by hand. Even in this mode the house load is served first, and the Export state of charge is a floor the battery discharges towards, not a promise of full export current for the whole three hours; how much goes out still depends on your load and solar at the time.
The CT coil limitation you must know about
There is one documented catch that matters for anyone watching their own energy. While the feature is exporting, the system switches into Selling First mode, and Sunsynk states that this disables the CT coil that reads your home load. In plain terms, you will not see your house consumption in the app during the export window, because the sensor that measures it is turned off in that mode. Sunsynk says firmware to keep the CT active during Flux export is in development, but at the time of writing that is a future fix, not a shipped one.
Is the beta reliable enough to trust?
From the documentation rather than from running it, the manual windows do the core scheduling and keep you fully sighted, while the integration trades that visibility for convenience and still carries a beta warning. The two hand-set windows are the reliable base. I have not run the manual timer and the live-price feature together, so treat combining them as a plan rather than a tested setup: if you trial both, watch which layer the inverter actually obeys, and keep the timer rows as a fallback so a beta hiccup lands on a sane schedule rather than on nothing.
If you do trial the live-price feature, treat it the way you would any beta on hardware that moves real money: turn it on when you can watch it for a few days, compare what it does against your own understanding of the windows, and know that you cannot see house load while it exports. If that blind spot bothers you, stay on the manual timer until the CT firmware ships.
Deye Flux settings use the same platform
Sunsynk hybrids are built on the Deye platform, so the underlying settings behave almost identically. The difference is the app in front of them. A Deye on its own cloud may not expose the same one-click Octopus Flux button that Sunsynk Connect does, so on a Deye you usually set the two windows manually through Time of Use.
Enable Time of Use first, because on Deye it is the master switch that makes the scheduled rows take effect at all. Then set a grid-charge row across 02:00 to 05:00 to fill the battery, and configure the mode and a discharge row so the battery can export into the 16:00 to 19:00 peak. Check the exact field names against your model’s manual, because Deye’s SG02, SG03 and SG04 families label current limits and export modes differently. I have not commissioned a Deye myself, so treat this as the manual-based method, not a bench-tested one.
What you can safely change and what you cannot
Setting timer windows, target states of charge and export permission is normal user-level configuration on these inverters. You can adjust the two Flux windows, watch a full cycle, and change them back if the result is not what you expected.
Keep these outside a Flux settings experiment: the Low Batt, Shutdown and Restart protection values, the grid-code and anti-islanding parameters, the CT or export-meter wiring, and any firmware or installer menu. If your battery has a communicating BMS and the inverter and BMS disagree about voltage, that is a support and protocol question, not something a timer change will fix. Record the current state with a screenshot before you change anything, so one test does not become six untraceable edits.
Sources and evidence
Primary references checked on 16 July 2026:
- Sunsynk, How to use the Octopus Flux feature (setup path, beta status, CT coil and Selling First limitation).
- Sunsynk, How to use the Octopus Agile tariff (related live-price setup in Connect).
- Octopus Energy, Octopus Flux (02:00 to 05:00 charge window, 16:00 to 19:00 export peak, solar, battery, smart meter, export MPAN and MCS eligibility).
- Octopus Energy, Intelligent Octopus Flux (the Octopus-controlled version, where Octopus schedules your battery rather than Sunsynk Connect; this guide covers the manual windows and the Sunsynk Connect live-price beta, not Intelligent Octopus Flux).
- Deye, product manual catalogue (Time of Use and export-mode fields by model family).
My first-hand contribution is the Sunsynk 3.6 ECCO, Fogstar and Solar Assistant timer mechanism, including the force-charge permission chain and the rule never to leave a current limit at zero after a crash. I run that on Octopus Go, not Flux, so the Flux windows and the beta Connect integration come from the documentation above rather than from my own Flux install. A sceptical reader should confirm the live Octopus rates and windows for their region, and check the Sunsynk feature’s current beta status, before relying on either.
The next move
Set the two windows by hand first: a grid-charge row across 02:00 to 05:00 to your chosen target, and an export-permitting mode with discharge allowed across 16:00 to 19:00. Watch one full day and confirm the battery fills overnight, covers the house through the peak, and sells any surplus into it. Only once that fixed foundation works should you decide whether the beta live-price feature is worth turning on, knowing it will hide your house load while it exports until the CT firmware arrives.
