Battery Arbitrage & SEG: How to Earn £300–£700 a Year From Your Battery

What Is Battery Arbitrage?

Battery arbitrage is the practice of charging your home battery when electricity is cheap and discharging it — either for self-consumption or grid export — when electricity is expensive. It treats your battery like a small-scale energy trader, buying low and using or selling high.

The economics work because electricity prices vary significantly throughout the day. Off-peak overnight rates on time-of-use tariffs like Octopus Go can be as low as 7–9p/kWh, while peak evening rates reach 24.67p/kWh. A 10kWh battery cycling this spread once per day generates meaningful savings or income.

Combined with solar panels and the Smart Export Guarantee (SEG), a well-configured battery system can earn £300–£700 per year on top of its self-consumption savings.

How Time-of-Use Tariffs Make It Work

Standard electricity tariffs charge a flat rate regardless of when you use power. Time-of-use (ToU) tariffs price electricity differently by time of day, reflecting the actual cost of generating and distributing power.

The key tariffs for battery arbitrage in 2026 are:

• Octopus Go: A cheap overnight rate (typically 7–9p/kWh for 4–5 hours from around midnight) and a standard daytime rate. Simple and effective for basic charge-at-night, use-in-day arbitrage.
• Octopus Flux: Three distinct rates — cheap overnight import, standard daytime, and a premium export rate in the evening peak (typically 5–7pm). Designed specifically for battery owners who want to both import cheaply and export at a premium.
• Intelligent Octopus Go: Uses smart EV charger or battery integration to automatically charge during the cheapest overnight windows, which can extend beyond fixed off-peak hours when grid demand is genuinely low.
• Agile Octopus: Half-hourly pricing that tracks wholesale electricity prices. Highest complexity but best opportunity — prices occasionally go negative, meaning you are paid to import electricity.

For most homeowners, Octopus Flux is the sweet spot: it offers the best combination of cheap overnight import and premium export without requiring active management of every half-hour window.

The Best Tariffs for Battery Arbitrage in 2026

Tariff rates change regularly, but the typical spread that makes arbitrage viable looks like this:

• Octopus Flux overnight import: 7–10p/kWh (midnight to 5am)
• Octopus Flux daytime rate: 22–26p/kWh
• Octopus Flux evening peak export: 25–32p/kWh (4pm to 7pm)
• Octopus Go overnight import: 7–9p/kWh (midnight to 5am)

The strategy with Flux is to charge overnight at the cheap import rate, then either use that electricity during the expensive daytime period (avoiding the 22–26p rate) or export it during the 4–7pm peak at the premium rate.

The export premium is the key: if you charge 10kWh at 8p and export at 30p, the gross spread is 22p/kWh — £2.20 per full cycle. Over 300 cycles per year, that is a significant income stream.

How Much Can You Realistically Earn?

The honest answer depends on battery size, tariff, and how actively you optimise. Realistic estimates:

• 5kWh battery on Octopus Go (use only, no export): Shifting overnight cheap electricity to replace daytime grid use — around £200–£300/year in bill reduction
• 10kWh battery on Octopus Flux (charge and export): Charging overnight at ~8p and exporting at peak rate — £350–£500/year in combined saving and income
• 10kWh battery with solar on Flux: Overnight cheap import + daytime solar self-consumption + evening peak export — £500–£700/year or more

These figures assume daily cycling, which requires a battery with sufficient cycle life warranty. Foxstar systems offer 6,000+ cycles (12-year warranty on 13.5kWh, 16+ years at one cycle per day), making daily arbitrage financially sustainable within warranty.

Smart Export Guarantee: The Export Side

The Smart Export Guarantee (SEG) requires licensed energy suppliers to pay for every unit of electricity you export to the grid. For battery arbitrage, the key distinction is between fixed SEG rates and time-of-use export tariffs:

• Fixed SEG rates: Providers like Octopus Outgoing (12p), E.ON (13p), and British Gas (15.1p) pay a flat rate for all exports regardless of time. Good Energy offers 25p fixed. Simple but lower income than time-of-use export.
• Octopus Flux export: Pays a premium for exports during the evening peak (around 25–32p/kWh). This is where the arbitrage income comes from — exporting battery-stored electricity during the highest-value window.

The key requirement: to access SEG payments including Flux export rates, your solar and battery system must be MCS certified. This is why certification matters — it is the gateway to all export income. We register your system for SEG as part of installation.

Which Batteries Work Best for Arbitrage?

The key factors are tariff integration, cycle life, and round-trip efficiency:

• Foxstar / FoxESS: Integrates natively with Octopus Flux and Intelligent Octopus, allowing automatic scheduling of charge and discharge windows. 6,000+ cycle warranty (12 years on 13.5kWh). Strong choice for arbitrage-focused installations.
• Tesla Powerwall: 3,000+ cycle warranty at full depth of discharge. Good software but less direct Octopus tariff integration than Foxstar. Still supports manual scheduling for arbitrage.
• SIG Energy: Competitive pricing with solid cycle warranty. Good for self-consumption; less mature tariff integration than Foxstar for arbitrage use.

Both Foxstar and Powerwall achieve 90%+ round-trip efficiency. For arbitrage, Foxstar's Octopus integration is a meaningful practical advantage. See our full comparison in the Foxstar vs Tesla Powerwall guide.

Solar + Battery: The Complete Strategy

The most effective approach layers solar generation with battery arbitrage:

1. Overnight cheap import (midnight–5am): Battery charges to full from grid at 7–9p/kWh
2. Morning solar generation (7am–noon): Solar charges battery or powers home — battery is partially discharged first to make room for solar
3. Afternoon peak solar (noon–4pm): Solar powers home loads; surplus charges battery or exports at standard SEG rate
4. Evening peak export (5pm–7pm): Battery exports to grid at premium Flux rate (24–32p/kWh)
5. Evening home use (7pm–midnight): Remaining battery charge powers home, avoiding standard rate electricity

For Cornwall holiday let owners, battery arbitrage is particularly attractive: during low-occupancy winter periods, the battery can cycle daily for income even when solar generation is modest, providing year-round returns.

Is Battery Arbitrage Worth It?

For most households installing solar, adding a battery with good arbitrage capability strengthens the financial case significantly. The additional arbitrage income can reduce the battery's payback period by 2–3 years compared to self-consumption alone.

For households without solar, buying a battery purely for arbitrage is marginal at current prices — the returns are modest without the solar layer. On Octopus Flux specifically, a standalone battery can generate £200–£300/year in savings and income, depending on usage, but the real returns come when solar is part of the picture.

The practical advice: if you are installing solar and considering a battery, choosing one with strong time-of-use tariff integration costs the same as one without it — but opens up significantly better long-term economics. It is not a reason to delay solar; it is a reason to choose the right battery from the start.

Book a free home survey. We assess your roof, consumption patterns, and tariff options and provide an honest projection of arbitrage and self-consumption returns before you commit to anything.