Most energy tariffs in the UK work on a simple principle: you pay a fixed unit rate per kWh, maybe with a slightly cheaper overnight rate if you’re on Economy 7. Octopus Agile is different in a way that sounds complicated until you understand why it matters. Every 30 minutes, your unit rate changes to reflect the actual wholesale price of electricity on the grid. When demand is low and renewables are generating well — typically between midnight and 7am — the rate can drop to 1p/kWh or, on good nights, go negative. When everyone’s putting the kettle on between 5pm and 7pm, the rate can spike to 50p or 80p/kWh.

For most people on a flat tariff, this variability doesn’t mean much. You can’t really shift your life around wholesale electricity prices with any precision. But if you’ve got a home battery, it changes everything.

How the battery arbitrage works

The idea is straightforward. Your battery charges automatically during cheap overnight periods — say, 1am to 6am when Agile rates might average 5-8p/kWh. During the expensive evening peak, 4pm to 7pm, your home runs from the stored battery power rather than the grid. You avoid buying electricity at 50p/kWh and instead use what you bought at 5p/kWh a few hours earlier.

Octopus publishes the next day’s half-hourly prices every afternoon at around 4pm. Open-source tools like Predbat can read these prices via the Octopus API and schedule your battery’s charge and discharge cycles automatically overnight, optimising around the cheapest windows. You don’t have to think about it day to day.

Add solar panels to this setup and the savings compound further. During sunny daylight hours, your solar generation charges the battery for free. Cheap overnight rates fill any remaining capacity. The battery then covers your evening usage. On good days in spring and summer, you might spend almost nothing on grid electricity.

Typical 12-month savings for a 5kWp solar and 16kWh battery system on Agile with Predbat automation run to £1,800-£2,500 in 2026, compared with £1,200-£1,400 on a flat tariff with the same hardware. The tariff choice is adding £600-£1,000 per year in savings on top of what the hardware alone would give you.

What you need to get started

First, you need a smart meter. Not an older SMETS1 from before 2019 — specifically a SMETS2 meter, or a SMETS1 meter made by Secure. Octopus needs to read your consumption data remotely every 30 minutes to apply the correct Agile rate, and that requires second-generation smart metering. If you’re unsure what generation you have, check the meter itself or ask Octopus — they can look it up on your account.

If you don’t have a SMETS2 yet, you can request a free upgrade through your supplier. It typically takes a few weeks to arrange and there’s no charge. Allow two weeks after installation for the meter to fully register and for Octopus to start billing on it.

Second, you need a compatible home battery. The Agile + Predbat automation works well with a range of inverter and battery combinations, but has strongest support for GivEnergy, Solis, SolarEdge, and Huawei systems. Tesla Powerwall works with Agile but uses a different scheduling approach through the Tesla app rather than Predbat. Check the Predbat compatibility list before purchasing if Predbat automation is important to you.

Third, you need a home assistant running Predbat. That sounds more technical than it is — Predbat runs on Home Assistant, which is free open-source software that runs on a Raspberry Pi or similar. Many battery installers now configure this as part of an installation package rather than leaving it to the customer to set up.

The honest caveats

Agile Octopus isn’t right for everyone. The evening peak prices are genuinely high — in July 2026, the 4pm-7pm window is regularly 50-80p/kWh. If you don’t have a battery and can’t shift your usage away from peak times, you’ll likely pay more on Agile than on a flat tariff. The tariff is designed for households that can actively manage when they consume electricity.

The variability also means your bill isn’t predictable in the way a flat rate is. Some months with good overnight rates and solar generation you’ll pay very little. A grey December without much solar and with high overnight wholesale prices will look different. For households who want predictability above optimisation, a time-of-use tariff like Octopus Go — with a fixed cheap overnight rate rather than variable wholesale rates — gives most of the battery benefits with less complexity.

That said, for households with solar and battery already installed, or planning to install both: Agile is worth the comparison. The saving over a standard tariff or even Octopus Go is meaningful enough to justify the setup.

Getting the most out of it

If you’re already an Octopus customer, switching to Agile is done online through your account in a few minutes. If you’re switching supplier, Octopus typically activates the smart meter connection within 14 days of your supply switch.

Spend the first month watching the Predbat schedules and checking whether your actual consumption patterns match what the system expects. Most households need a few weeks of tuning — adjusting the minimum battery charge level, setting up home appliances as shiftable loads if you have smart plugs, and calibrating how aggressively Predbat charges on negative-rate nights versus saving battery capacity for potential cheap windows the next morning.

Once it’s running well, most people check it once a week at most. The system does its own optimisation. Your electricity bill quietly gets smaller.