Plug-in Solar With Octopus Agile: Maximising Time-of-Use Savings

Time-of-use tariffs like Octopus Agile can amplify your plug-in solar savings by 30-40%. Here's how to combine solar, battery, and smart tariffs.

Plug-in solar saves money by displacing grid electricity. A time-of-use tariff like Octopus Agile amplifies those savings by making grid electricity cheaper when you do need it — and more expensive during the peak hours your solar already covers.

The combination is powerful. Here's how it works.

How Octopus Agile Works

Octopus Agile tracks wholesale electricity prices and updates your tariff every 30 minutes. Prices are lowest overnight (typically 7-12p/kWh), rise during the day (15-25p/kWh), and peak between 4pm-7pm (often 30-50p/kWh, occasionally higher).

This matters because your plug-in solar generates during the day, covering midday consumption when Agile prices are moderate. But the real value is in what happens at the edges — cheap overnight imports and expensive peak-hour displacement.

Solar + Agile (No Battery)

Without a battery, Octopus Agile still benefits plug-in solar owners. Your solar covers daytime consumption at 15-25p/kWh equivalent. In the evening peak (4-7pm), you're back on the grid at 30-50p/kWh.

Typical savings increase: 10-15% more than a standard flat-rate tariff, because Agile's daytime rates are often lower than the flat rate, meaning you "save" less per kWh displaced — but your evening and overnight costs may also be lower.

The honest truth: without a battery, Agile's benefit over a flat tariff is modest for plug-in solar. The real gains come when you add storage.

Solar + Agile + Battery: The Sweet Spot

This is where the economics get interesting. A portable power station like the EcoFlow DELTA 2 (1024Wh capacity) or Anker SOLIX C1000 Gen 2 paired with plug-in solar and Octopus Agile creates three income streams:

1. Solar self-consumption (daytime). Your solar charges the battery during the day. Free electricity stored for later.

2. Cheap overnight charging. When solar isn't generating, the battery charges from the grid at 7-12p/kWh overnight.

3. Peak-hour displacement. Between 4-7pm, when Agile prices spike to 30-50p/kWh, you run from the battery instead of the grid.

The maths on a typical winter day:

Battery charges overnight at 8p/kWh: 1kWh × 8p = 8p cost
Battery discharges during 4-7pm peak at 40p/kWh average: 1kWh × 40p = 40p saved
Net gain per cycle: 32p
Over 5 months of winter (150 days): £48 from arbitrage alone
Add summer solar charging (free) displacing peak use: another £30-50

That's £70-100/year extra savings on top of normal solar self-consumption — just from smart tariff management.

Octopus Go vs Agile vs Flux

Octopus Agile: Variable 30-minute pricing. Best if you're hands-on and willing to shift loads. Highest potential savings but more unpredictable.

Octopus Go: Guaranteed 7p/kWh for 6 hours overnight (23:30-05:30). Simpler, more predictable. Great for overnight battery charging without watching prices.

Octopus Flux: Designed specifically for solar + battery households. Time-of-use import and export rates. Offers the best export rates — which matters if you're one of the few plug-in solar owners who can access export payments. Off-peak import at ~15p/kWh, peak export at higher rates.

Our recommendation: For plug-in solar with a battery, start with Octopus Go. It's the simplest — guaranteed cheap overnight rate, no price-watching needed. Upgrade to Agile once you're comfortable with the system and want to maximise savings.

Smart Plugs Make This Work

You need visibility of both generation and consumption to time things properly. A Shelly Plus Plug UK on your inverter output shows real-time solar generation. An Emporia Vue 3 on your main supply shows whole-home consumption.

With both, you can see exactly when you're generating more than consuming (time to charge the battery) and when consumption exceeds generation (time to draw from battery or grid).

If you use Home Assistant (see our HA monitoring guide), you can automate this entirely — battery charges from solar when available, from grid when prices drop below a threshold, and discharges during peak pricing.

Is It Worth Switching?

If you already have plug-in solar and a battery, switching to a time-of-use tariff is a no-brainer. The additional savings are £70-100/year for essentially zero extra effort once set up.

If you have plug-in solar without a battery, the benefit is marginal (10-15% improvement). A battery is the unlock — but it's also a £500-1000+ additional investment that changes the payback calculation.

The combined payback:

800W plug-in solar kit: ~£500-950
EcoFlow DELTA 2 battery: ~£850
Total investment: ~£1,350-1,800
Annual savings (solar + tariff arbitrage): ~£250-320
Payback period: 4.5-6 years

Compared to solar-only payback of 5-7 years, the battery + smart tariff combination actually reduces your overall payback period by accelerating savings. Counter-intuitive, but the arbitrage income makes the battery earn its keep.

The Bottom Line

Time-of-use tariffs like Octopus Agile, Go, and Flux are a natural companion to plug-in solar. The combination of free daytime solar generation, cheap overnight grid charging, and expensive peak-hour battery discharge creates a savings engine that flat-rate tariffs can't match.

Start with plug-in solar. Add a smart plug for monitoring. When you're ready, add a battery and switch to a time-of-use tariff. That's the sequence that maximises your return.

For battery comparisons, see our evening use battery guide. For monitoring options, see our smart plug comparison.