Octopus Agile import · Outgoing fixed 12p export
The tariff
The tariff matters every bit as much as the hardware, because it decides what every stored kWh is actually worth. And ours changed while we were still waiting for install day. If you're planning a battery system around any time-of-use tariff, this one's worth two minutes.
The Flux plot twist
The original business case was built on Octopus Flux, the classic battery tariff with a cheap overnight window and a 30p evening export peak. The plan was dead simple. Charge cheap overnight, force-export the battery into the 4pm to 7pm peak, profit. Then in March 2026 Flux (and Intelligent Octopus Flux) closed to new customers, months before our panels went on the roof. So much for the plan.
Lesson one: don't pin a multi-year payback sum on one tariff sticking around. Tariffs are products, and products get pulled. Model your second-best option too. We hadn't, and re-planning under time pressure was no fun at all.
What we run now
| Side | Tariff | Shape |
|---|---|---|
| Import | Octopus Agile | Half-hourly dynamic pricing, published around 4pm for the next day and capped at £1/kWh. Cheap slots sit in the low teens. Evening import peaks run from the mid-20s in summer up to the high 30s in winter. |
| Export | Outgoing Octopus (fixed) | Flat 12p/kWh, all day, every day. No export peaks on this one. Boring on purpose, because it's a guaranteed floor. |
Export isn't paid yet. We can't earn anything for export until the final installation certification goes in, which can take a month or two from install day. The inverter still exports the surplus once the battery's full, we just hand it to the grid for free, and the stats honestly report £0 export revenue. On a sunny June day that's £2 or more sailing out of the meter for nothing, which is a decent reason to chase the paperwork.
Here's the surprise. Losing Flux's 30p export peak only cost me around 10% of the projected year one return. Under Agile the battery's job flips from exporting at a peak rate to not importing at a peak rate. Dodging expensive evening import is worth roughly as much as the old peak export was, and Predbat reorganised the whole strategy on its own the day we swapped the rate sensors over. The only real loss is on true surplus (battery full, house satisfied), which now earns 12p instead of 30p.
A possible upgrade later: Agile Outgoing does half-hourly export pricing, uncapped, with no exit fees. For battery owners who can export selectively into the evening spikes it can beat a flat 12p, and winter wholesale prices occasionally clear 50p or more. I'll switch if the data shows my would-be Agile export revenue reliably beating 12p. That comparison is exactly the kind of question this site's dataset exists to answer.
Why Octopus at all?
Higher flat export rates do exist elsewhere (E.ON around 16.5p, British Gas around 15p), but they all want you importing with the same supplier on a flat or simple time-of-use tariff. For a Predbat home, the cheap-import arbitrage on Agile is the bigger prize anyway. Octopus also has the best API in the business, and the whole automation stack hangs off it.
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