Octopus Agile, Flux, and Cosy: Which Smart Tariff Works Best with Solar?

Smart electricity tariffs have transformed the economics of solar panels and battery storage in the UK. The right tariff can add £300-600 per year to your system's returns — or the wrong choice can leave savings on the table. Octopus Energy's three main smart tariffs — Agile, Flux, and Cosy — each suit different setups. This guide explains which one maximises savings for your specific configuration.

How Smart Tariffs Work with Solar and Battery

All three tariffs share a core concept: electricity prices vary throughout the day rather than being fixed. The goal is to use electricity when it is cheap (charging your battery or running appliances) and avoid using grid electricity when it is expensive (evenings). For solar and battery owners, smart tariffs add a second dimension: you can also earn more by exporting at the right times, not just saving by importing at the right times.

The economics depend on your setup. Solar-only households benefit primarily from shifting flexible loads (washing machine, dishwasher, car charging) to cheap off-peak periods. Solar plus battery households can also use the battery to arbitrage price differences — charging cheaply overnight and discharging during expensive peak periods. Solar plus battery plus EV charger households have the maximum number of controllable loads and benefit most from smart tariff optimisation.

Octopus Agile: Best for Battery Owners and Active Managers

Agile prices vary every 30 minutes based on wholesale electricity prices and are published the evening before. Prices can be as low as 2-5p/kWh during cheap overnight windows (typically midnight to 6am) and as high as 35-100p/kWh during demand peaks (weekday evenings in winter). Prices occasionally go negative — meaning Octopus pays you to use electricity — during periods of high renewable generation.

For battery owners, Agile is the most powerful tariff available. A smart battery like the Tesla Powerwall or GivEnergy can be programmed (manually or via automation) to charge when prices fall below a threshold and discharge when they rise above it. In 2025, informed Agile users with a 10kWh battery saved an additional £400-700 per year on top of solar generation savings. The catch is that Agile requires engagement — prices must be monitored and charging schedules updated. Automation via apps like Octopus Assistant or GivEnergy's smart scheduling helps, but Agile rewards active users disproportionately.

Octopus Flux: Best for Solar and Battery Combined

Flux is specifically designed for solar and battery customers. Unlike Agile's variable prices, Flux operates on three fixed price periods: a cheap off-peak import period (typically midnight to 5am), a standard daytime rate, and a peak evening rate (4pm to 7pm). It also includes an export rate — the price Octopus pays for electricity you export to the grid — that varies by time of day.

The Flux model is optimised around a simple strategy: charge the battery cheaply overnight, let solar top it up during the day, and export any surplus at the higher daytime export rate. Discharge the battery during the peak 4-7pm window to avoid expensive grid electricity. The fixed time-of-use structure makes Flux easy to automate and plan around — it does not require daily price monitoring like Agile.

For households with a mid-sized battery (7.5-10kWh) and a 4kW solar system, Flux typically outperforms Agile when managed via automated scheduling. The simplicity is the advantage. A 9.5kWh GivEnergy battery on Flux with a 4kW solar system in Yorkshire typically generates combined savings and export income of £900-1,300 per year at 2025 energy prices.

Octopus Cosy: Best for Solar-Only Homes or Passive Savers

Cosy operates on a simpler two-period structure: a cheap rate from midnight to 9am and from 1pm to 4pm, and a standard rate at all other times. There is no variable pricing — the cheap rate is fixed. For solar-only households (no battery), Cosy's lunchtime cheap window from 1-4pm aligns with peak solar generation, meaning surplus solar energy that is exported is partly replaced by cheap Cosy imports if needed — useful for households with moderate self-consumption.

Cosy is easier to understand and plan around than Agile or Flux. For households that want meaningful savings without managing complex schedules, Cosy typically saves £150-350 per year compared to a standard variable tariff — less than Flux or Agile but with minimal effort required. For passive or time-poor households, Cosy is the pragmatic choice.

Which Tariff Is Right for Your Setup?

For solar-only homes, Cosy provides the simplest meaningful savings without active management. Agile is worth considering if you are willing to run time-shifted loads like EV charging and the washing machine during cheap windows. For solar plus battery homes, Flux provides the best automated performance with moderate management effort, while Agile rewards active users with higher but less predictable savings. For solar plus battery plus EV charger, Agile or Flux both excel — the choice depends on whether you prefer simplicity (Flux) or maximum optimisation (Agile).

All three tariffs require a smart meter to be installed. Octopus Energy installs smart meters free of charge as part of onboarding. The tariffs can be switched between at any time, allowing you to adapt as your circumstances or preferences change. We advise Yorkshire customers on tariff selection as part of our system handover, and our monitoring setup makes it straightforward to track which tariff is performing best for your setup.