Octopus Agile + Solar: 2026 Guide to Maximum Savings
Octopus Agile combined with solar PV and a Predbat-automated battery is the highest-saving setup available to UK homes in 2026. Typical 12-month combined savings: £1,800–£2,500 on a 5kWp solar + 16kWh battery system, versus £1,200–£1,400 on a flat tariff with the same kit. The uplift comes from charging the battery on negative or near-zero Agile half-hours and discharging (or exporting) when Agile spikes above 25p/kWh. Best practical kit: Solis LV hybrid + Fogstar 16.1kWh + Home Assistant + Predbat.
Octopus Agile is the UK’s most variable consumer electricity tariff. Half-hourly prices follow wholesale market conditions — you’ll see prices as low as -5p/kWh (Octopus pays you to import) on windy Sunday nights and as high as 35p/kWh at 5pm on a cold weekday in winter. The spread is what makes Agile genuinely lucrative for battery-storage homes.
How Agile actually works
Every day at around 4pm, Octopus publishes the next day’s 48 half-hourly prices in p/kWh. The price you pay in any given half-hour is fixed for that half-hour but varies materially across the day. Cheap windows are typically overnight (Sunday/Monday early hours) and midday (when solar oversupply pushes wholesale prices down). Expensive windows are typically 4–7pm on weekdays in winter.
The four ways to save on Agile + solar
- Self-consume your solar in real time. Solar generation during the day reduces import — saves you whatever Agile’s rate is at that half-hour.
- Charge the battery from solar surplus. Excess solar that would have been exported (at SEG rates) goes into the battery for evening use instead. Saves you the difference between SEG export rate and evening Agile import rate.
- Charge the battery from cheap Agile half-hours. When Agile drops to 2–8p/kWh overnight, import to the battery. Discharge against your evening peak rate of 25–30p/kWh.
- Export at peak Agile half-hours. Octopus Agile Outgoing pays Agile’s peak rates for export. Charge the battery in cheap windows; export at expensive windows. Pure arbitrage.
Why Predbat is the key
None of the above happens automatically with a standard battery setup. The battery’s default behaviour is ‘charge from solar, discharge to home load’. Adding price-awareness requires software that reads the next 48 half-hourly prices, forecasts your home’s consumption and solar generation, and decides what the battery should do each half-hour.
Predbat is the open-source Home Assistant add-on that does exactly this. It connects to Octopus’s Agile API, to your inverter’s control interface, and to your house’s real-time consumption data, and runs an optimisation every half-hour. Result: a battery that actively trades against Agile.
Indicative savings (Spectrum customer data)
| Setup | Annual electricity bill | Annual savings vs no-solar baseline |
|---|---|---|
| No solar, no battery, Octopus Flexible | £1,500–£1,800 | Baseline |
| 5kWp solar, no battery, Flat tariff | £850–£1,000 | £500–£800/year |
| 5kWp solar + 16kWh battery, Flat tariff | £200–£400 | £1,100–£1,400/year |
| 5kWp solar + 16kWh battery + Agile + Predbat | -£100 to £200 | £1,500–£1,900/year |
Some Predbat-optimised customers run net-negative annual bills — Octopus pays them more in Agile Outgoing export and negative-price import than the standing charge and remaining import costs. This isn’t the normal outcome (it requires aggressive Predbat tuning, large battery, decent solar) but it’s achievable.
Want this setup on your home?
We’ll design the solar, fit the battery, and configure Home Assistant + Predbat as part of the install. One quote, one contract.
Request a QuoteStep-by-step: getting onto Agile
- Confirm you have a SMETS2 smart meter sending half-hourly readings (look at any recent bill — it’ll say).
- If you’re not already with Octopus, switch to Octopus Flexible (free, ~21 days).
- Inside your Octopus account, switch to Octopus Agile and Octopus Agile Outgoing simultaneously.
- Wait 24–48 hours for the tariff change to settle.
- If you have a battery installed, configure Predbat on Home Assistant — or have Spectrum do it as part of the install.
Sizing for Agile
Battery sizing for Agile differs slightly from sizing for a flat tariff. On flat tariff, you only need capacity to cover evening peak (4–10pm). On Agile, you also benefit from charging through cheap overnight windows for next-day use. That means sizing for cover of two peak windows simultaneously (your evening + the next morning) plus some headroom for export arbitrage.
Practical sizes:
- 3-bed semi, no EV, Agile + Predbat: 13–16kWh
- 4-bed detached, no EV, Agile + Predbat: 16kWh
- 4-bed + EV, Agile + Predbat: 16–24kWh
- Heat pump household, Agile + Predbat: 24–32kWh
See our battery sizing article for a fuller treatment.
Common Agile mistakes
- Going on Agile without a battery. Saves nothing (often loses money) if you can’t shift consumption. Agile makes sense for battery owners or heavy off-peak users.
- Going on Agile with a battery but without Predbat. Captures maybe half the available savings. The battery still has to decide when to charge/discharge — doing that with manual schedules can’t track Agile’s daily volatility.
- Mixing Agile Outgoing with a closed-ecosystem battery (Powerwall pre-2025 firmware). Newer Powerwall firmware can do Octopus integration, but Predbat’s granularity is sharper.
- Setting Predbat once and forgetting it. Predbat’s parameters benefit from monthly review as seasons change. Spectrum’s standard install includes 90 days of post-commissioning Predbat tuning.
FAQs
Is Octopus Agile worth it without solar?
Worth it if you have a battery and Predbat (battery-only arbitrage works). Worth it if you can heavily shift consumption (EV overnight charging, washing/drying off-peak). Not worth it for households that just run normal weekday evening peaks — you’d pay more on Agile than on Flexible.
How much does Predbat cost?
Predbat itself is free open-source software. It runs on Home Assistant, which is also free but needs a small home-server device — a Raspberry Pi 4 or 5 (£75–£120) plus a microSD card. Spectrum supplies and configures this as part of a battery install for typically £200–£300 all-in.
Can I run Predbat with a Tesla Powerwall?
Predbat has some Powerwall integration but Tesla’s closed-ecosystem firmware doesn’t expose the fine-grained control needed for best-in-class Agile arbitrage. Most Powerwall customers use Tesla’s own Octopus tariff integration, which captures perhaps 85% of available savings. For maximum optimisation, Solis + Fogstar + Predbat is the stronger combination.
What happens if Octopus changes the Agile pricing rules?
Agile’s pricing methodology has been adjusted twice since 2018 (changes to the cap, smoothing of extreme prices). Each change has tweaked the upside slightly but not removed it. Predbat updates rapidly when methodology changes — the open-source community is quick. Half-hourly settlement is now market-mandated, so some form of Agile-style tariff will keep existing.
Do I need three-phase supply for Agile?
No — Agile is available on standard single-phase domestic supply. Most UK homes have single-phase. Three-phase is needed only on heavy-load homes (heat pumps + EVs + large electric appliances) and adds DNO approval steps to the install. We confirm at site survey.
Can I export to Agile Outgoing if I have flat-rate Agile import?
Yes — Octopus allows mixed Agile Outgoing (variable export) with any of their import tariffs. Most Predbat customers run both Agile import and Agile Outgoing for maximum optimisation, but it’s flexible. Switching either tariff doesn’t affect the other.
How long does it take to switch to Agile?
Once you’re an Octopus customer (existing or new), the switch to Agile is requested through your Octopus account and takes 1–2 working days. Switching to Octopus from another supplier first takes ~21 days, then add 1–2 days for the Agile change. Plan the battery and Predbat install around this.
Related reading
- What is Predbat? Solar battery optimisation explained
- Best solar battery for Octopus Agile in 2026
- UK solar export tariff comparison 2026
- Home Assistant for Solar PV: 2026 setup guide
- Lowering your electricity bills with solar
For the full Spectrum service overview see smart energy management.
Speak to Spectrum Energy Systems
MCS NIC200223. We design, fit and configure Solis + Fogstar + Predbat for Octopus Agile across the East Midlands. One installer, one quote, one warranty.
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