Octopus Go, Cosy, and Intelligent

Three time-of-use tariffs, three different approaches to cheap electricity. Which one actually saves money for your setup — and which one could cost you more than staying on a flat rate?

How time-of-use tariffs work

A flat-rate tariff charges you the same price for every unit of electricity — currently around 24.5p/kWh at the Ofgem cap. A time-of-use (TOU) tariff charges different rates at different times. You get a deep discount during off-peak hours (typically overnight) and pay a premium during peak hours.

The logic is simple: the grid has excess capacity at night when demand is low. Suppliers can buy wholesale electricity cheaply and pass that saving on, as long as you shift your consumption to match. The question is always whether you can genuinely shift enough usage to come out ahead.

All three Octopus TOU tariffs require a smart meter with half-hourly readings enabled.

Octopus Go

The original and most popular time-of-use tariff. Go gives you a fixed 4-hour off-peak window from 00:30 to 04:30 at a heavily discounted rate — currently around 8.5p/kWh. The rest of the day runs at roughly 28p/kWh — higher than the flat cap rate.

Who it suits

• EV owners who charge at home: this is the core use case. If you charge your EV overnight, Go can cut your driving costs to under 3p per mile. On 8,000 miles a year, that's roughly £190 vs £700 on a flat tariff — a saving of over £500/year just from charging.
• Battery owners: charge a home battery at 8.5p overnight and discharge during the day when you'd otherwise pay 28p. The spread (roughly 20p/kWh) means a 10 kWh battery cycling daily could save £700/year — but battery degradation, round-trip losses, and the fact that you won't cycle every day reduce this to more like £350–£500/year in practice.
• Timer-friendly households: if you can run your dishwasher, washing machine, and tumble dryer overnight on delay timers, you shift another 2–4 kWh daily to the cheap window.

Who it doesn't suit

Households without an EV or battery who can't shift at least 30–35% of their consumption into the 4-hour window. The higher daytime rate means you need substantial off-peak usage to break even. A family that uses 10 kWh during the day and only shifts 2 kWh to off-peak will pay more than on a flat tariff.

Octopus Cosy

Designed specifically for heat pump owners. Cosy provides two cheap windows: 04:00–07:00 and 13:00–16:00 at roughly 12p/kWh. The peak rate (16:00–19:00) is higher at roughly 40p/kWh, and the rest of the day sits around 25p.

Who it suits

• Heat pump households: the morning window aligns with pre-heating your home before waking, and the afternoon window lets you boost hot water or pre-heat before the evening peak. A well-insulated home can "soak up" heat during the cheap windows and coast through the expensive ones.
• Households with thermal mass: homes with thick walls, underfloor heating, or concrete floors hold heat well. Pre-heating during cheap windows and releasing that stored heat during expensive ones is the core strategy.

Who it doesn't suit

Homes that aren't well-insulated. If your house loses heat quickly, pre-heating at 12p just means the heat pump has to run again at 25p or 40p to maintain comfort. You end up heating twice for the same result. Before switching to Cosy, insulate first.

The 40p/kWh peak window (16:00–19:00) is punishing. If you can't avoid heavy electricity use during those 3 hours — cooking, heating, lighting — the penalty eats into your savings.

Octopus Intelligent

Intelligent takes a different approach. Rather than giving you fixed cheap windows and expecting you to manage your usage, it integrates with your EV charger and smart home devices to automatically shift demand to the cheapest half-hours throughout the night.

The off-peak rate (roughly 8.5p) applies from 23:30 to 05:30, and Octopus can also extend cheap-rate windows dynamically when wholesale prices dip during the day. You set your target (e.g., "car needs 80% charge by 7am") and the system handles the scheduling.

Who it suits

• EV owners with a compatible charger: Intelligent supports a specific list of EV chargers and EVs for smart charging. Check the Octopus Intelligent device list before assuming your setup qualifies.
• Hands-off users: if you want the savings without setting timers and managing schedules yourself, Intelligent does the work. The automation is genuine — it learns your patterns and optimises accordingly.

Who it doesn't suit

Users without a compatible EV and charger. The smart scheduling features are the whole point — without them, Intelligent is just a less flexible version of Go with a slightly longer off-peak window. Check compatibility before signing up.

The break-even calculation

The fundamental question with any TOU tariff: can you shift enough consumption to off-peak to offset the higher peak rates?

As a rule of thumb: if you can shift less than 30% of your total consumption to off-peak hours, a flat tariff is cheaper. Between 30–50%, TOU tariffs roughly break even. Above 50%, TOU tariffs deliver meaningful savings.

An EV charging 7–10 kWh overnight immediately puts most households above the 30% threshold. A battery adds another 5–10 kWh of shiftable load. Timer-controlled appliances add 2–4 kWh. If you have two or more of these, a TOU tariff almost certainly saves money.

Use our tariff switching calculator to model your specific usage pattern — it accounts for your consumption, EV charging, battery, and timer usage to give you a direct flat-vs-TOU comparison.

Which one to choose

• EV + no heat pump: Go or Intelligent, depending on whether you want manual control or automation.
• Heat pump + no EV: Cosy, if your home is well-insulated and has thermal mass.
• EV + heat pump: Go is usually the best fit — the overnight window lets you charge the EV, pre-heat the home, and top up hot water all at the cheap rate.
• Battery + solar: Go — charge the battery overnight at 8.5p, use solar during the day, discharge the battery in the evening. The 20p spread per kWh is where the money is.
• None of the above: stay on a flat tariff. Without shiftable loads, TOU tariffs are a trap.

Switching is free and fast

Switching to any Octopus tariff is free, takes about 2 minutes online, and there are no exit fees if it doesn't work out. You can try a TOU tariff for a month, check whether your bills went up or down, and switch back to flat if the maths doesn't work. There's genuinely no risk to experimenting.

Model the numbers first with our tariff switching calculator, then make the switch with confidence.