Time-of-Use Tariffs & Solar: Save More
How do time-of-use tariffs work with solar?
Time-of-use (ToU) tariffs charge different electricity rates at different times of day — typically: cheap overnight (7–10p), standard daytime (~24p), and expensive peak (~30–36p). For solar + battery owners, this creates a profit opportunity: charge the battery from solar (free) or overnight cheap rate, then export or self-consume during expensive peak periods. ToU tariffs add £200–£520/year to solar + battery savings compared to flat-rate tariffs.
How Time-of-Use Tariffs Create Value
The arbitrage opportunity:
With a flat tariff, every kWh costs the same (~24.5p) regardless of time. With a ToU tariff, prices vary:
| Period | ToU Rate | What You Do | |--------|---------|-------------| | Overnight (cheap) | 7–10p | Charge battery + EV from grid | | Morning (standard) | ~24p | Battery powers home until solar kicks in | | Midday (solar peak) | N/A (free solar) | Solar powers home + charges battery | | Peak demand (expensive) | 30–36p | Battery exports at premium OR powers home (avoiding expensive import) | | Evening (standard) | ~24p | Battery covers remaining evening |
Value per kWh cycled through your battery: - Buy overnight at 10p → use during peak at 36p = 26p profit per kWh - On a 10kWh battery: £2.60/day = £949/year in pure arbitrage
Combined with solar self-consumption: - Solar (free) → charge battery → export at peak (24–36p) = 24–36p value per kWh - Far higher than SEG fixed rate (4.5p)
Source: Octopus Flux/Go rate structures; arbitrage calculations.
Best Time-of-Use Tariffs for Solar
Octopus Flux (best for battery owners): - Off-peak: ~10p (02:00–05:00) - Standard: ~26p (05:00–16:00 & 19:00–02:00) - Peak import: ~36p (16:00–19:00) — AVOID importing - Peak export: ~24p (16:00–19:00) — MAXIMISE exporting - Best for: solar + battery (export stored energy at peak)
Octopus Go (best for EV owners): - Off-peak: 7.5p (00:30–05:30) - Standard: ~24.5p (rest of day) - No premium export or peak penalty - Best for: solar + EV (cheap overnight EV charging)
Octopus Agile (for advanced users): - Half-hourly pricing (changes every 30 minutes based on wholesale market) - Can be as low as 0p (or negative!) during oversupply - Can be as high as 50p+ during peak demand - Best for: tech-savvy users with automated battery management - Risk: unpredictable — requires active management or smart inverter
Intelligent Octopus Go (for smart EV owners): - Extends the 7.5p overnight window based on when your EV needs to be charged - Smart scheduling optimises charging around your departure time - Best for: EV owners with compatible smart chargers
Source: Octopus Energy tariff details March 2026.
Setting Up Your System for ToU Tariffs
- Get a smart meter (required for all ToU tariffs) — free from your supplier
- Choose a battery with ToU automation (GivEnergy has built-in Flux/Go modes, Tesla supports Octopus)
- Set charge/discharge schedules — your inverter manages when to charge from grid and when to discharge
- Avoid peak import (16:00–19:00 on Flux) — use battery or solar during this window, never grid
- Run heavy appliances during solar hours or overnight cheap window — NOT during peak
- Monitor your savings — your app shows how much you save from tariff optimisation vs flat rate
- Review every 6 months — tariff rates change. Ensure you are still on the best deal.
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