How does Solar and Grid calculate the best time to charge?

Solar and Grid aims to charge from your solar panels as much as possible, as long as it’s not more expensive than regular smart charging. Here’s how we do it:

If you're on a variable rate tariff

Our solar algorithm calculates the blended cost of charging using both your solar panels and grid electricity to determine the cheapest times to charge. 

Since solar panels can’t always generate all the energy needed, we calculate the combined cost of using both solar and grid energy to determine the actual cost during sunny periods. When you solar charge, ‘cheapest’ might be when it’s sunniest, but sometimes it may be cheaper overnight. 

Example 

Let’s say your solar panels provide 50% of the energy for your car, and you’re on the Octopus Go energy tariff. In this case, your electricity costs 15p per kWh, except between 00:30 and 04:30, when it costs 5p per kWh. 

During the day, with 50% solar and 50% grid energy, the effective cost is 7.5p per kWh. However, the overnight cost is 5p per kWh, so we prioritise charging during this off-peak window. If more charging is needed, we schedule it when solar production is highest.

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If you're on a flat-rate tariff

With a flat-rate energy tariff, solar energy is considered free. Charging with solar energy is always cheaper than using grid energy, so we maximise the use of solar energy for charging your EV as much as possible.

Keep your tariff up to date

Adding your tariff allows us to prioritise charging your EV during the lowest-cost periods from the grid when your solar panels are not producing energy. This means more savings for you and a smarter, more efficient way to power your EV. 

If you haven’t added your energy tariff to the app or have recently changed it, please follow these simple steps to update it: 

1. Open the ev.energy app on your mobile phone.
2. Go to the 'Tariff' section in the 'Smart' tab.
3. Provide your tariff via one of the options available.