Octopus Flux explained: who it actually suits

Flux is a tariff designed around a battery. It divides the day into three priced periods, and the whole point is that you buy when electricity is cheap, sell when it is expensive, and let stored energy carry you across the gap.

Without storage, most of the mechanism is unavailable to you. Without solar, the tariff is not available at all: the eligibility rules require panels. Both facts are worth knowing before the sales conversation, and both come from the tariff’s own page.

The three periods

The shape, with the windows from the tariff’s published description; the rates themselves vary by region and change over time:

A cheap overnight window, 02:00 to 05:00. Low import price, and a low export price to match. This is when a battery tops up from the grid.

A standard daytime period. Ordinary import and export rates for the bulk of the day.

An expensive evening peak, 16:00 to 19:00. High import price, and a high export price with it. This is when a battery discharges, either into your house to avoid importing at the peak rate, or into the grid to be paid the peak export rate.

Both import and export are priced in every period. That symmetry is what makes the tariff work, and it is unusual: on most arrangements your export rate never changes, so holding export back for the evening earns nothing. On Flux it is the entire game.

Who it suits, and who cannot have it

A household with solar and a battery. The designed fit, and per the eligibility rules, the only fit: Flux requires a smart meter with half hourly readings, solar panels, a home battery, and both your import and export accounts with Octopus. The panels do not need to have been installed by Octopus. Solar fills the battery during the day, the battery covers the evening peak, and surplus is exported when the export price is highest.

A household with a battery and no solar is not eligible for Flux, but is not out of the game: pure arbitrage, charge overnight cheaply, discharge at the peak, works on an EV tariff like Intelligent Octopus Go at 8p off peak against a capped standard rate of 26.11p, which is currently one of the widest spreads available.

A household with solar and no battery. Eligible on paper if a battery is fitted later, but as a plain solar household the shape works against you: your generation peaks in the middle of the day, which is the standard period, not the expensive one. You would export at the middling rate and import at the peak rate in the evening, which is the wrong way round. A flat export tariff is the simpler, better fit until storage arrives.

The setup that decides whether it pays

Three practical requirements, each of which has caught people out:

Your inverter must be schedulable. The battery has to charge and discharge at specific times of day, 02:00 and 16:00 are not negotiable with the grid. If your system cannot be programmed against a timetable, the tariff cannot be exploited.

Grid charging must be enabled. Some solar-oriented installations only charge the battery from generation. On Flux, overnight grid charging is half the mechanism, and it is the half that works in the winter months when the roof produces little.

Your export must be metered half-hourly. Being paid a peak export rate requires the meter to know when you exported, which is why the smart meter sits in the eligibility list rather than the small print.

Confirm all three with your installer before switching, not afterwards.

The failure mode

The common disappointment is a household that switches to Flux, does not change how the battery is scheduled, and finds the bill has gone up.

That is exactly what should happen. The tariff has an expensive evening peak, and if nothing is arranged to avoid it, you simply pay peak rates for evening consumption while gaining nothing from the cheap window you are not using.

Flux is not a passive tariff. It rewards a system that is actively scheduled against it, and it quietly penalises one that is not. If you want a tariff you never think about, this is not the shape to choose, and that is a legitimate preference rather than a failure.

Checking whether it would suit you

Do this before switching:

1. Get your half-hourly consumption data and total how much falls in the 16:00 to 19:00 window. For many households this is the heaviest three hours of the day: cooking, heating coming on, everyone home.
2. Estimate how much of that your battery could cover, capped by its usable capacity and its continuous power rating.
3. Multiply the covered amount by the difference between the peak import rate and the overnight import rate on the current Flux pricing for your region. That is the arbitrage saving.
4. Subtract what the higher peak rate costs on the consumption you cannot cover.

If step three comfortably exceeds step four, the tariff is worth taking. If it is close, a simpler flat-rate arrangement will be less work for a similar result, and the package comparison method applies here exactly as it does to any conditional offer.

It is one option among several

Flux is not the only battery-friendly tariff, and the supplier offering it also runs a flat export tariff, a tracking tariff and the EV-oriented one above, each suiting a different pattern. Rates and periods change, so check the current terms on the supplier’s own pages rather than any summary, including this one.

Then model it with your own consumption profile and your own usable battery capacity in the ROI calculator, which supports the Flux-style three period structure and keeps import and export separate in every period. A blended average will hide the entire effect, and the entire effect is the reason to consider the tariff at all.