If you have solar and a battery, Octopus Flux is usually the stronger pick, because it gives you a cheap overnight charging window and a high 16:00 to 19:00 export peak that you can set once and leave alone. If you have a battery but no solar, Flux is not open to you at all, so the real choice becomes Agile import for arbitrage alongside Agile Outgoing for timed export, and you have to be willing to reschedule the battery as prices move. The whole decision turns on two questions: do you have solar, and do you want fixed daily windows or live wholesale prices?
This page is about the whole-household battery decision: what you pay to import, what you earn to export, and what stored energy saves when you use it yourself. It is not only the export-rate head-to-head. Every pence figure here is a July 2026 snapshot that moves with your postcode and the wholesale market, so treat the method as the durable part and confirm live rates on Octopus before you design any payback around them.
Flux or Agile for a battery: the short answer
Choose Flux if you have solar and a battery and you want predictable windows you can automate with a simple timer. Choose Agile, meaning Agile import paired with Agile Outgoing export, if you have no solar or you want to track wholesale prices and are happy to reschedule the battery. Flux needs solar. Agile does not.
| Question | Octopus Flux | Agile (import + Agile Outgoing) |
|---|---|---|
| Needs solar? | Yes, plus a home battery and an MCS certificate | No |
| How prices are set | Fixed daily windows | Half-hourly, tracking wholesale, published around 4pm for the next day |
| Cheap charging | 02:00 to 05:00 super off-peak | The cheapest half-hours, which change every day |
| Export | 16:00 to 19:00 peak, currently a high rate | Agile Outgoing, half-hourly and uncapped |
| Effort | Set the windows once | Reschedule or automate daily |
| Price protection | Flexible three-band tariff; rates can change with notice, no exit fees | Import capped at 100p/kWh; export uncapped |
| Best fit | Solar plus battery, low effort | No solar, or a household that wants to chase wholesale |
What are you actually choosing between?
Flux and Agile are not two versions of the same thing. Flux is a structured product built around fixed clock windows. Agile is a raw wholesale feed that you schedule the battery against yourself.
Octopus Flux is a combined import and export tariff aimed squarely at solar and battery homes. It has super-cheap import between 02:00 and 05:00 to top the battery up, a standard rate through the middle of the day, and a peak window from 16:00 to 19:00 when both import and export are priced highest. Flux is symmetrical, so in each window the import and export prices mirror each other, and it is a flexible tariff: the unit rates and standing charge move with the wholesale market and can change with notice, though there are no exit fees. As a regional example in the July 2026 snapshot that meant roughly 15p to charge overnight, around 24p to 25p for standard daytime import, and about 26.6p for both peak import and peak export between 16:00 and 19:00. Octopus publishes no headline Flux rate, so enter your postcode for your own figures. Standard Flux gives you those windows to control yourself. Intelligent Octopus Flux is the automated version, where Octopus schedules a compatible battery for you.
Agile Octopus is the half-hourly import tariff. Prices follow the day-ahead wholesale market and are published around 4pm for the following 24 hours, so you can see tomorrow’s 48 prices before they apply. It is capped at 100p/kWh, and it can go negative during oversupply, which is when you are effectively paid to charge. Agile Outgoing is its export twin: a half-hourly export price that also tracks wholesale and is uncapped. Its average sits well below the Flux peak, but the best few evening half-hours can climb far higher, and both the level and the shape of the day shifted when Octopus revised the tariff in early 2026, so check the current Agile Outgoing prices for your region rather than trusting a single headline average.
The number that matters is the gap between what you pay to charge and what you earn or save when the battery discharges. On Flux that gap is fixed and visible. On Agile it changes every half-hour, which is the whole point and the whole burden.
Do you have solar, or only a battery?
This is the fork that settles most of the decision, and it is the part the generic comparisons skip. Octopus Flux requires solar. To join it you need solar panels, though they do not have to be Octopus-installed, a home battery, a smart meter sending half-hourly readings, an export MPAN, and an MCS certificate for the installation.
If you own a battery but no solar, Flux is simply not available to you: its eligibility rules require solar panels, so a battery-only home cannot join whatever it might do with the peak window. Your realistic options become Agile import for tariff arbitrage, or a tariff with a fixed cheap overnight window. The usual battery-only pick is standard Octopus Go, which gives the whole home a low fixed rate across a set overnight window of roughly five to six hours, so you charge the battery in that window and run the house off it by day. Do not reach for Intelligent Octopus Go here unless you also run an eligible electric car or compatible charger, because it is an EV tariff that Octopus unlocks by controlling the car’s charging, and a battery-only home with no EV does not qualify. Cosy Octopus is the better fit if you also have a heat pump, because its three daily cheap windows suit heating rather than a single battery fill. So for a battery-only home the Flux versus Agile question really resolves to Agile if you want to chase wholesale, or Octopus Go if you want a fixed cheap window and less effort.
If you do have solar and a battery, both are open to you, and the rest of this page is about which pays more for your usage pattern. One caveat to note now: as of 16 July 2026 the fully automated Intelligent Octopus Flux is closed to new sign-ups, paused during a stretch of volatile evening-peak pricing, while standard Octopus Flux remains open and existing Intelligent customers keep their tariff. The automated version is also limited to a list of eligible battery brands. Treat standard Flux as the open route today, and reconfirm on Octopus whether Intelligent Flux has reopened, and whether your battery is supported, before you count on it.
How to work out which tariff pays more
A home battery earns money two ways, and a fair comparison has to price both. The first is self-use: you charge cheaply, then discharge to avoid importing at an expensive rate. The second is export: you send stored energy to the grid for the export price. Every comparison should run through the same short calculation.
For self-use, the value of each kWh you put into the battery is:
value per kWh charged = (round-trip efficiency × avoided import price) − charge price
Round-trip efficiency for a modern LiFePO4 home battery is typically 85 to 92%, so 90% is a fair working figure. That efficiency is why you never get out what you put in, and why a thin price spread can vanish once losses are counted.
Flux worked example (solar and battery). Charge overnight at about 15p, then use that energy in the evening instead of importing. Discharge after 19:00 and you avoid the day rate of about 25p; discharge into the 16:00 to 19:00 peak and you avoid the higher peak import, about 26.6p in this regional snapshot. Taking the day rate as the conservative case, value per kWh charged is (0.90 × 25) − 15, which is 22.5 − 15, or about 7.5p per kWh, and a little more if you time the discharge into the peak band. Fill 5kWh overnight and that leg alone is worth roughly 37p a night before any solar export. Any genuine solar surplus you cannot use goes out in the 16:00 to 19:00 window at about 26.6p, the same price you would pay to import in that window, so exporting surplus and self-using it are close to a wash there. The real Flux money is the cheap-night-to-expensive-evening spread, plus a strong peak for surplus you would otherwise waste.
Agile worked example (no solar). Suppose the cheapest overnight block averages 18p and the evening peak you avoid averages 33p, which is the kind of spread Agile can show when wholesale is volatile. Value per kWh charged is (0.90 × 33) − 18, which is 29.7 − 18, or about 11.7p per kWh. That beats the Flux arbitrage leg on a good day. The catch is that Agile spreads vary a lot month to month, with some 2026 stretches expensive and others soft, and on a flat day the spread can collapse below the Flux windows. You are trading a guaranteed spread for a variable one.
Turning pence into pounds a year. Scale the spread by how much you actually cycle. The Flux arbitrage leg at about 7.5p per kWh is worth roughly £135 a year if you move 5kWh a night, and closer to £220 a year for a 10kWh battery cycling about 8kWh a night, before any solar export. The Agile no-solar leg at about 11.7p per kWh works out near £215 a year at 5kWh a night on the volatile spread above, but that figure swings with the market and shrinks on flat days. Solar export on Flux stacks on top of the arbitrage number: a 4kW array feeding the 16:00 to 19:00 peak in summer can add tens of pounds more, though it earns almost nothing in midwinter. Treat these as order-of-magnitude figures from the snapshot rates, not a quote, and re-run them on your own live prices and usage.
The export-versus-self-use rule falls out of the same maths: only export a kWh when the export price beats what that kWh would have saved you by displacing an import. Because Flux prices import and export the same in each window, self-use wins by the margin of your round-trip losses for anything the house can absorb in the peak, so self-consume first and export only the surplus you genuinely cannot use. Buying off-peak power specifically to export at the peak is a different move, and on Flux it is a legitimate one: charge at about 15p, export at about 26.6p, and after 90% round-trip efficiency you still clear roughly 9p per kWh, which is exactly what Intelligent Octopus Flux automates. Just rank it below self-use, because a kWh you self-consume avoids the same peak price without the export leg, and on Agile, where the export average is far lower, grid-charge-to-export rarely covers its losses at all.
Fixed windows or wholesale chasing: manual or automation?
Flux and Agile ask for very different amounts of your attention, and that effort is a real cost.
Flux windows are fixed, so you set the battery once. I run a Sunsynk hybrid with Fogstar batteries and schedule the charge window in Solar Assistant, and a fixed window like 02:00 to 05:00 is a one-time job: the inverter timer fills the battery and stops. A basic charge schedule in any hybrid inverter does the same. Nothing has to react to tomorrow’s prices.
Agile is the opposite. To earn its spread you have to charge in the cheapest half-hours and discharge into the most expensive ones, and those move every day. You either do that by hand each afternoon when the next day’s prices publish, or you automate it. Home Assistant and several third-party apps can read the Agile price feed and drive the battery, but that is a standing system you build and maintain, not a set-and-forget window. Intelligent Octopus Flux is the exception that automates for you, though it is closed to new sign-ups as of 16 July 2026 and limited to supported battery brands when open.
The plain trade-off: Flux is low effort with a fixed spread, Agile is higher effort with a spread that is sometimes better and sometimes worse. Pick honestly based on whether you will actually do the scheduling, or build the automation, over the long run.
The losses and reserve most comparisons ignore
Three things quietly shrink the return, and marketing-led comparisons tend to leave them out.
- Round-trip losses. At about 90% efficiency, roughly a tenth of every kWh you charge never comes back out. Price your spread on the energy you get out, not the energy you put in.
- Reserve you keep back. If you hold a minimum state of charge for backup or battery health, that capacity is not cycling and not earning. Your usable daily throughput is smaller than the nameplate kWh.
- The peak-window clash. On Flux, the 16:00 to 19:00 export peak is also when the house is waking up and cooking. Every kWh you export is a kWh you did not self-use, so the two goals compete for the same stored energy.
None of these change which tariff to pick on their own, but they decide whether a marginal spread is worth chasing at all. I model export income conservatively for exactly this reason: the headline rate is never the money that lands.
Which should you pick?
Match the tariff to your setup and your appetite for effort.
- Solar and battery, want low effort: standard Flux. Fixed windows, a strong export peak, and a charge schedule you set once.
- Solar and battery, happy to automate: the Agile pair can beat Flux when wholesale is volatile, but through calmer stretches the roughly 26.6p Flux peak has often been hard to beat. Agile spreads vary month to month, so test it against your own recent 30 to 90 day price history before switching.
- Battery but no solar: Flux is not available. Use standard Octopus Go for a fixed cheap overnight window and least effort, or Agile import if you want to chase wholesale, and treat Agile Outgoing export as a minor add-on that rarely beats self-use after losses. Intelligent Octopus Go only applies if you also run an eligible EV or compatible charger.
- Want it hands-off: Intelligent Octopus Flux automates the battery for you, but it is closed to new sign-ups as of 16 July 2026, so unless it has reopened and your brand is supported you are automating Agile yourself.
Whichever way you lean, the durable advice is the same: work out your own spread with the formula above, count the losses and the reserve, and confirm the live rates on Octopus before you commit. The winning tariff is the one whose numbers survive your own arithmetic, not the one with the best marketing.
Can I get Octopus Flux with a battery but no solar?
No. Octopus Flux requires solar panels alongside the battery, plus a half-hourly smart meter, an export MPAN, and an MCS certificate. A battery-only home cannot join Flux. Your route is standard Octopus Go, which gives the whole home a fixed cheap overnight window of roughly five to six hours, or Agile import if you want to track wholesale, paired with an export tariff only if you actually export. Intelligent Octopus Go is an EV tariff and needs an eligible car or compatible charger, so it is not a battery-only option.
Is Agile Outgoing worth it for battery export?
It can be, but temper expectations. Agile Outgoing is uncapped and tracks wholesale half-hourly, so its average sits well below the Flux peak while its best evening half-hours can climb much higher; check the current prices for your region rather than a headline average. If you have solar, the roughly 26.6p Flux peak usually exports better. Without solar, Agile Outgoing is your main timed-export route, and it only pays if you schedule discharge into its best blocks.
Can I switch between Flux and Agile later?
Yes. Octopus smart tariffs have no exit fees, so you can move between them as your setup or the market changes. A sensible approach is to start on the tariff that matches your effort level, log your import cost and export income for a couple of months, then re-run the spread calculation before deciding whether the alternative would actually pay more.
Is Octopus Flux worth it in winter with little solar?
Yes, mostly. The cheap-night-to-expensive-evening charging arbitrage works every month, whatever your panels are doing, and that spread is where most of the Flux saving comes from. What goes quiet in winter is the 16:00 to 19:00 export peak, because a UK array generates little from December to February and you self-use nearly all of it, so there is rarely a surplus to sell into that window.
Because Octopus smart tariffs have no exit fees, you could move to a wholesale tariff for the darkest months and back to Flux for summer. For most homes the arbitrage leg alone keeps Flux worthwhile the whole year, so seasonal switching is optional effort rather than something you have to do.
Do Flux and Agile have different standing charges?
Both carry the usual daily import standing charge set by your region and network operator, not a tariff-specific penalty, and you pay one on either tariff. The export side adds no second standing charge: export credits arrive without a separate daily charge on top. Standing charges are rarely what decides between Flux and Agile, so compare them on the unit rates and export prices above. Check your postcode’s exact standing charge on Octopus, because it varies across the country and moves with the price cap.
Sources
- Octopus Energy, Octopus Flux (windows, eligibility, solar and battery requirement).
- Octopus Energy, Intelligent Octopus Flux (automation, eligible battery brands, availability note).
- Octopus Energy, Agile Octopus (half-hourly pricing, 100p/kWh cap, plunge pricing).
- Octopus Energy, Outgoing Octopus and Agile Outgoing (uncapped half-hourly export).
- Octopus Energy, Intelligent Octopus Go (whole-home overnight window, battery-only route without solar).
- Octopus Energy, Cosy Octopus (three daily cheap windows, heat-pump homes).
The round-trip efficiency range for LiFePO4 home batteries is a typical measured figure, not a manufacturer guarantee. My first-hand contribution is the scheduling experience on a Sunsynk and Solar Assistant setup and the habit of modelling export income conservatively; the pence figures are a July 2026 snapshot, last checked 16 July 2026, and must be confirmed against your region’s live rates on the Octopus tariff pages linked above before you design any payback around them.
