Solar with Octopus Go and time-of-use tariffs in 2026

Time-of-use (TOU) tariffs let UK households pay different rates for electricity depending on the time of day. Combined with solar and a battery, they can shift the financial case meaningfully — sometimes turning a marginal installation into a clear win, sometimes adding complexity for negligible gain. This guide separates when stacking is worth it from when it isn't.

The shapes of UK TOU tariffs

Three patterns dominate UK TOU offerings in 2026:

• Off-peak / cheap-overnight tariffs. Octopus Go is the canonical example: a cheap window of around 4–5 hours overnight (usually 23:30–05:30) charged at roughly 7–9p/kWh, with the rest of the day at a higher standard rate. Designed originally for EV owners.
• Cheap-period heat-pump tariffs. Cosy (Octopus) and similar offer two or three cheap windows during the day to align with heat-pump heating cycles. The "shoulder" rates are mid-priced; peak hours are expensive.
• Half-hourly wholesale tariffs. Octopus Agile updates the import price every 30 minutes based on wholesale electricity. Occasionally goes negative; occasionally spikes during peak demand. Rewards active management.

There's also Octopus Outgoing Fixed (a flat 15p/kWh for export) and Outgoing Agile (variable export). Most homeowners on a TOU import tariff stay on a flat export tariff for simplicity.

Solar alone, no battery

A TOU import tariff with solar but no battery does relatively little. The cheap window is overnight when there's no solar generation, so you don't gain on the cheap rate. The standard daytime rate matters more — and most TOU tariffs have a higher daytime rate than the average flat tariff.

In short: solar without battery + TOU import is usually worse than solar without battery + flat tariff. Stick with a flat tariff and a high SEG export rate (see the SEG explainer).

Solar plus battery — where it gets interesting

A battery is the multiplier. Three patterns are worth knowing:

Pattern 1: Charge cheap overnight, discharge during peak

Charge the battery from cheap overnight grid electricity (Octopus Go at ~9p), then discharge during peak rates (15:00–19:00 on standard tariffs at 28p+). The arbitrage is around 19p per kWh discharged. With a 5kWh battery cycling once a day, that's around £35 a month, £400 a year — independent of any solar generation.

This is why a battery + Octopus Go often pays back faster than a battery + flat tariff, even before you count the solar contribution.

Pattern 2: Solar fills the battery during the day, discharges in the evening

Standard "self-consumption" pattern. Solar generates during the day, fills the battery, and the battery discharges from sunset onwards — displacing peak-rate grid imports. Works on a flat tariff or a TOU tariff; the TOU tariff's higher peak rate makes the saved kWh more valuable.

Pattern 3: The hybrid

Solar fills the battery during sunny days; on cloudy days the battery charges from the cheap overnight grid window instead. Most modern hybrid inverters can be configured for this with a simple time-based rule. Captures both wins without needing constant adjustment.

When TOU stacking is worth it

A few conditions to look for:

• You have a battery. The arbitrage doesn't work without one.
• Your daytime electricity use is moderate — high enough that solar self-consumption is significant, but not so high that you have nothing left for the battery.
• You're comfortable with one tariff change a year to track which TOU offer is best. Octopus, EDF, Eon, and OVO all run their own; the leaderboard moves.
• Your home has reasonable battery capacity (5kWh+). Sub-3kWh batteries don't store enough overnight cheap to matter.

When to skip TOU and use a flat tariff

• No battery, or only a small one
• Most of your usage is overnight already (some shift workers)
• You hate the idea of checking your tariff at all
• Your solar export is the dominant value (large system, small daytime use, no battery) — a flat import tariff plus a premium export tariff is simpler

A worked example

Say you have a 5 kWp solar system in the West Midlands, a 5 kWh battery, and average household electricity use (~3,500 kWh/year, including some EV charging).

• Flat tariff, no TOU: annual benefit roughly £700–£900 (solar self-consumption + a moderate SEG export rate).
• Octopus Go + Octopus Outgoing Fixed: annual benefit roughly £900–£1,200. The extra ~£300 comes from overnight battery arbitrage on days where solar can't fill it.

The exact number depends on your usage pattern, the panel direction, and how aggressively you use the EV-charging slot. The savings calculator lets you compare both setups for your home.

What to actually do

For a homeowner considering a battery and a TOU tariff:

1. Get the battery sized roughly 1–2 kWh per kWp of solar — the battery storage guide goes into sizing.
2. After installation, sign up to the cheapest TOU import tariff you can. Octopus Go is the most popular but not always the best — check the live rates.
3. Pair it with the highest export tariff you can find — see the SEG explainer.
4. Configure your inverter or battery system to charge from the grid only during your cheap window and to prioritise self-consumption during the day. Most modern hybrid inverters do this in one or two settings.

Related

• Solar battery storage UK — worth it in 2026?
• Smart Export Guarantee (SEG) explained
• Are solar panels worth it in the UK in 2026?
• Use the savings calculator