Your car charged at lunchtime. Was it on the cheap rate? With Intelligent Octopus Go, the clock alone doesn't tell you. Octopus can give you extra smart-charge slots outside the usual 23:30–05:30 window. Wattlas shows those slots beside your charging readings and electricity rates.
One Sunday, two reasons for cheaper electricity
On 13 September 2026, this connected Wattlas account had extra smart-charge slots at 11:00–11:30 and 12:00–14:30. There was also an Octopus Weekend Happy Hour free electricity session from 12:00–14:00. They overlap, but they aren't the same thing: a smart-charge slot gives the off-peak rate; the free session brings the rate down to zero.
- The purple area shows when the car charged.
- The blue line shows the electricity rate on the right-hand axis.
- The notes below the chart identify the smart-charge slots and free session.
The car took 14.19 kWh: 14.08 kWh from the grid and 0.11 kWh from solar and battery. These are this account's readings, not a prediction of what another household will use or save.
What did it cost?
The cost breakdown puts 13.75 kWh of grid charging in the free session and the remaining 0.33 kWh at 6.9p/kWh. The home used free electricity too: 6.74 kWh.
The displayed total for the day is 70p, including a 63p standing charge. This is Wattlas's calculated breakdown using the connected readings and rates, not an Octopus bill.
Weekend Happy Hours have a 16 kWh cap per booked hour. The 20.49 kWh free-import row covers two hours; it does not prove that each hour was within its cap or confirm Octopus's final credit. See our Happy Hour guide for the rules and how to check the calculation.
See it with your own readings
Connect your Octopus account and a supported charger to see charging beside your tariff. Add a compatible solar or battery connection for the home-energy view shown here. Connected monitoring requires Wattlas Plus.
Wattlas uses available Octopus account data to show smart-charge slots and supported free sessions. Coverage depends on the data available for your account and day. Charging schedules stay in Octopus or your charger app; Wattlas doesn't control the charge. Your supplier's bill remains the final record of what you owe.
If you're still choosing a plan, see how Intelligent Octopus Go's cheaper hours and smart slots compare with other EV tariff features.
Sources
Octopus Energy - Intelligent Octopus Go
Octopus Energy - how Intelligent Octopus Go works
The Octopus Energy logo is a trademark of its owner and is shown
only to identify the company. Wattlas isn't affiliated with Octopus
Energy.
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Solar, battery, car charging and energy tariff costs, all in Wattlas.
