Smart charging explained

If you’re charging an EV at home on a time-of-use tariff, smart charging is the difference between saving a bit of money and saving a lot. It’s worth understanding how it works, because the approach you take can add up to hundreds of pounds a year.

What smart charging actually means

A “dumb” charger starts as soon as you plug your car in and keeps going until the battery is full. Simple, but expensive if you plug in at 6pm when electricity is at its peak price.

A smart charger connects to your home WiFi and can be controlled remotely. At the most basic level, you can set a schedule: “only charge between midnight and 5am”. More advanced setups let Octopus’s systems take over entirely, choosing the cheapest possible times to charge your car without you needing to think about it.

Levels of smart charging

There are three levels, each building on the one before.

1. Manual scheduling

You set the times yourself through your charger’s app or, in some cases, through your car’s built-in charging schedule. You look at your tariff’s cheap window (Octopus Go is 00:30 to 05:30, for example) and tell the charger to only run during those hours.

This works perfectly well. You’ll get the cheap rate every night. The drawback is that it’s inflexible. If the cheap window changes, you need to update the schedule. If the grid has spare capacity at 3pm on a Tuesday and electricity is briefly cheap, your charger won’t know about it.

2. App-controlled scheduling

Smart chargers from Ohme, Zappi, Hypervolt and others let you set a target within their app: “I need 80% charge by 7am.” The charger’s own software works out when to run based on the tariff rate data it pulls from Octopus’s API. It picks the cheapest hours within the overnight window.

This is more convenient than manual scheduling and can save slightly more on Agile (where rates vary every half hour). For Go and Intelligent Go, where there’s a flat off-peak rate, it’s mostly about convenience rather than additional savings.

3. Full Octopus integration (Intelligent Go)

This is where it gets genuinely clever. On Intelligent Go, you connect your compatible charger (or supported vehicle) to Octopus’s systems through their app. You tell it what time you need the car and what charge level you’re after. Octopus then takes full control.

Their systems don’t just charge during the guaranteed overnight window (23:30 to 05:30). They also look for opportunities throughout the day when electricity is cheap. These are called bonus slots.

Bonus slots explained

Bonus slots are one of the best things about Intelligent Go, and they’re often misunderstood.

The national grid doesn’t run at a constant load. There are times during the day when supply exceeds demand, perhaps on a windy afternoon when the turbines are generating more than the grid needs. During these periods, Octopus can offer Intelligent Go customers the off-peak rate for additional charging.

You don’t choose when bonus slots happen. You don’t even need to know they’re happening. Octopus detects the opportunity, sends a signal to your charger, and it starts drawing power at the off-peak rate. When the window closes, it stops. Whenever smart charging is scheduled outside your off-peak window, the electricity for your whole home is also charged at the discounted rate during those slots.

How many bonus slots you get varies. Some weeks you’ll get several hours of additional cheap charging. Other weeks, very few. It depends entirely on grid conditions.

For bonus slots to work, your car needs to be plugged in (even if the battery isn’t empty) and you need a compatible charger or vehicle connected to Octopus’s system.

The 6-hour smart charging limit

From January 2026, Octopus enforces a 6-hour daily limit on smart charging at the discounted rate. This limit had always existed in the tariff terms, but previously wasn’t automatically enforced.

In practice, this means you get up to 6 hours of cheap smart charging every 24 hours. These hours may fall during the off-peak window (23:30 to 05:30), outside it, or a mix of both. If you need more than 6 hours to reach your target charge level, any additional time is billed at the standard day rate.

For most drivers, 6 hours at 7kW adds around 150 miles of range. That comfortably covers typical daily driving. If you regularly need more than that, it’s worth factoring this limit into your charging routine.

How much can you save?

The numbers depend on your mileage, your car’s efficiency and which tariff you’re comparing against. Here’s a rough illustration for a typical EV doing 8,000 miles a year:

• Standard flat rate (~24.5p/kWh): around £588/year
• Go overnight rate (~8.5p/kWh): around £204/year
• Intelligent Go with bonus slots (~7p/kWh effective): around £168/year or less

The jump from a standard tariff to Go or Intelligent Go is dramatic. The additional saving from smart scheduling and bonus slots over basic scheduled charging is smaller per session, but it compounds over time.

Use the EV calculator to get figures tailored to your actual car and mileage.

The charger app vs the Octopus app

This confuses a lot of new users. You’ll typically have two apps: one from your charger manufacturer (Ohme, myenergi, Hypervolt, etc.) and the Octopus Energy app.

The charger app is where you set up your charger initially, connect it to WiFi, update firmware and monitor charging sessions. It shows you detailed stats about each charge.

The Octopus app is where you link your tariff to the charger, set your departure time and target charge level for Intelligent Go, and see your energy usage alongside your bill.

Once you’ve done the initial setup and linked the two, you’ll mostly use the Octopus app for day-to-day control. The charger app becomes more of a diagnostic tool.

Getting started

1. Make sure your charger is compatible with Intelligent Go (or check if your vehicle has direct integration).
2. Install the charger and connect it to your home WiFi through the manufacturer’s app.
3. In the Octopus app, go to the Intelligent Go section and follow the steps to link your charger or vehicle.
4. Set your usual departure time and preferred charge level.
5. Plug in whenever you get home. The system handles the rest.

The whole point of smart charging is that once it’s set up, you stop thinking about it. You plug in, you unplug in the morning, and the cheapest possible electricity fills your car overnight.