The battery and Agile arbitrage concept
Energy arbitrage is the practice of buying something when it is cheap and using it when it is expensive. Applied to home batteries and Octopus Agile, it works like this: your battery buys electricity from the grid during Agile's cheapest overnight periods and stores it. During the expensive peak evening hours, your battery discharges that stored electricity into your home. You avoid buying expensive peak electricity because you already bought it cheaply at 3am.
Standard electricity tariffs do not reward this behaviour because the price is the same at 3am as it is at 6pm. Agile makes arbitrage worthwhile because the overnight-to-peak price spread is often 30-40p/kWh. A battery converts that price differential into real pound savings every day.
This is genuinely different from how most households think about home batteries. Many buyers purchase batteries primarily for solar self-consumption, which is valuable but depends on solar generation. Agile arbitrage means your battery creates value every single day, regardless of whether you have solar panels, regardless of the weather, and regardless of the season. The only requirement is that Agile overnight prices remain below Agile peak prices, which they have on every single day since the tariff launched.
Real-world figures: what a 10kWh battery earns annually
The headline arithmetic: charge a 10kWh battery at 3p/kWh average overnight Agile cost. Total charging cost: £0.30. Discharge that battery across the peak evening period when Agile is pricing at 35p/kWh. Value of electricity discharged: £3.50. Daily net saving: £3.20. Annual: £1,168.
The real-world figure is lower than this theoretical maximum, for three important reasons. First, batteries have charging and discharging losses of roughly 8-10%, so a 10kWh charge delivers approximately 9kWh of usable electricity. Second, not every evening reaches the 35p peak rate. In summer, Agile evening prices often run 10-18p/kWh, reducing the discharge value. Third, some days the battery is partially full from solar, so the overnight charge is partial rather than full, reducing the arbitrage volume.
Accounting for these factors, a realistic annual saving from a 10kWh battery on Agile is £400-600 per year. This figure assumes the battery completes roughly 300 full arbitrage cycles per year (not every day, accounting for partial cycles and days where solar pre-fills the battery) at an average spread of £1.50-2.00 per cycle.
With solar panels, the total battery value rises. The battery now serves both purposes: it captures surplus solar during the day (avoiding low-rate SEG export) and charges from cheap Agile overnight (for peak discharge). The combined annual value of a battery on an Agile and solar system is typically £800-1,200 per year.
Setup: how to programme your battery for Agile pricing
Getting your battery optimised for Agile requires telling it when to charge and when to discharge. The method varies by brand, but the core logic is the same across all systems.
The manual time-window approach (all batteries): Set a charging window of 1am-6am and a discharge window of 4pm-9pm. This captures the cheapest Agile period on most nights and avoids the most expensive peak on most evenings. Once configured, this runs automatically every day with no further input. It is not perfectly optimised, but it captures approximately 80-85% of the available arbitrage value.
The semi-manual approach: Check AgileAlert's live prices each evening around 9-10pm when the next day's prices are published. Identify the two cheapest hours in the overnight window and set your battery charging start time to target them. This takes two minutes per evening and improves your annual saving by approximately £40-80 compared to the fixed-window approach.
The automated approach (GivEnergy and Home Assistant): GivEnergy's native Agile integration automatically schedules battery charging during the cheapest periods each day. Home Assistant users with the Octopus Energy integration can create automations that trigger charging when prices fall below any threshold they choose. Full automation removes all manual effort and consistently captures maximum arbitrage value.
Which home batteries work with Agile?
Most modern UK home battery systems are compatible with Agile arbitrage through one of three routes: direct Agile API integration, time-window scheduling via app, or third-party Home Assistant integration.
GivEnergy: The best native Agile integration available in the UK market. GivEnergy's Eco mode connects directly to the Octopus Agile API, downloads the next day's price schedule, and automatically charges the battery during the cheapest periods. Suitable capacity options include 9.5kWh and larger units. A strong choice for Agile households who want automation without technical complexity.
Tesla Powerwall: Excellent hardware with 13.5kWh capacity and a polished app experience. Does not integrate directly with Agile pricing, but Time-Based Control mode allows you to set precise charging and discharge windows. The manual scheduling approach works reliably on Powerwall. For advanced users, third-party integrations via Tesla's API and Home Assistant allow price-responsive automation.
SolarEdge Home Battery: Integrates with SolarEdge inverters and schedules via the SolarEdge monitoring app. Time-window scheduling works well for Agile optimisation. The app allows you to set charging periods and priorities, including whether to prefer solar or grid charging. No native Agile API integration, but responsive to manual schedule adjustments.
Growatt: Popular budget option with third-party Home Assistant integration available. No native Agile API integration, but the Home Assistant community has developed solid integrations for Growatt systems that enable price-responsive automation. The hardware is cost-effective, making the total system cost lower, which improves payback calculations.
Solis: Strong Home Assistant community support. No native Agile integration but excellent third-party automation via the Solis-Home Assistant ecosystem. Hardware quality is high and pricing is competitive.
GivEnergy, Tesla Powerwall, Solis, SolarEdge: Agile compatibility in detail
For households specifically choosing a battery to maximise Agile performance, here is the full compatibility picture.
GivEnergy leads for Agile-native integration. The GivEnergy portal's Eco mode with Agile settings is the most straightforward automation available. You authorise your Octopus account, set your preferences, and the system handles daily scheduling automatically. The GivEnergy app is polished, support is UK-based, and the 9.5kWh unit suits most three-bedroom homes.
Tesla Powerwall is the strongest hardware choice if you prioritise build quality, warranty, and brand reliability over native Agile integration. The 13.5kWh capacity gives more daily cycling headroom. Time-Based Control mode is intuitive to configure. For technically confident users who want to add automation, the Tesla API and Home Assistant enable price-responsive charging.
Solis and SolarEdge both require Home Assistant or manual scheduling for Agile optimisation but are well-supported within the UK smart home community. If you are already a Home Assistant user, either brand integrates cleanly into an Agile automation workflow.
When does battery payback become viable?
A battery purchased primarily for Agile arbitrage, at a cost of £8,000-15,000 installed, at £400-600 in annual arbitrage saving, produces a standalone payback of 13-37 years. On those numbers alone, battery payback is marginal at best.
The economics improve substantially when you layer in solar. A battery added to an existing solar system improves self-consumption from 35-45% to 70-85%. The additional solar electricity captured by the battery, instead of being exported at 15p/kWh SEG, is self-consumed at 26p/kWh avoided cost. The difference is 11p/kWh across approximately 1,500 kWh per year: £165/year in additional value. Combined with arbitrage saving of £400-600/year, total annual battery value rises to £565-765/year. At that level, a £8,000 GivEnergy installation has an 11-14 year payback.
Battery prices have fallen consistently year on year. Installed costs for a 10kWh system in the UK have dropped from approximately £14,000 in 2020 to £8,000-10,000 in 2026. Continued cost reduction toward £6,000-7,000 by 2028-2029 will bring battery payback below 10 years for solar and Agile households, at which point batteries become straightforwardly economic for most homeowners who plan to stay in their property for 10+ years.
The environmental case: storing surplus wind, displacing peak gas
Your battery's environmental contribution goes beyond the economics. When you charge your battery on overnight Agile, you are drawing electricity from a grid that runs on surplus wind power. UK overnight generation is dominated by wind farms that cannot easily reduce output. The cheap Agile prices overnight signal this surplus. Your battery soaks it up rather than letting it go to waste.
When you discharge your battery during the 6pm-9pm peak, you are displacing electricity that would otherwise come from gas peaker plants. These are the most carbon-intensive and expensive generating assets on the UK grid, running only during demand peaks to fill shortfalls. Your 10kWh battery discharge during the evening peak replaces approximately 2.5-4kg of CO2 that a gas peaker would otherwise emit, every single day.
Across a full year of daily cycling, your battery prevents approximately 1-1.5 tonnes of CO2 emissions from gas peaking generation. That is a meaningful contribution, equivalent to taking a small car off the road for four to six months. The financial return and the environmental return align exactly. The cheapest electricity is always the surplus wind electricity, and the electricity you displace at peak is always the dirtiest gas generation. Your battery profits from doing the right thing for the grid.