How does Solar charging calculate the best time to charge?

The aim of Solar charging is to charge from your solar panels as much as possible, as long as it's not more expensive than regular smart charging. Here's an explanation of how we do it.

If you're on a variable rate tariff

Our Solar algorithm works out the blended cost of charging from your solar panels and uses this to decide when it is the cheapest to charge.

We know that we cannot always rely on your solar panels generating all the energy required to charge your car: some energy will be coming from your solar panels and some will be coming from the grid. We, therefore, calculate a blended cost to figure out the actual price of charging you during sunny times. If you're Solar charging, "cheapest" might be when it is sunniest - but sometimes it may actually be cheaper overnight.

See below for an example of how we calculate a blended price based on local (home) solar production.

For example, let's say your solar panels produce 50% of the energy used to power your vehicle, and you're on the Octopus Go tariff. In this case, your electricity costs 15p per kWh, except between 00:30 and 04:30 when it costs 5p. In this scenario, your effective cost of charging with 50% solar power and 50% grid electricity during the day is 7.5p per kWh.

However, we know that the cost will be 5p during the overnight off-peak window. Using that cheap energy is our priority, so we will fill those overnight slots up first. Then if your car needs more time to charge, we will schedule the remaining charge time when solar production will be at its highest.

If you're on a flat-rate tariff

If you have a flat rate tariff, our job is easy: we consider that solar energy costs you zero, so charging your car with at least some solar energy is always cheaper than charging completely from the grid. Therefore we will maximise as much as we can the amount of time we charge you from your solar panels.

Keep your tariff up to date

If you have not told us what tariff you're on, or you have changed tariff recently - please add your latest tariff information in the app! We cannot reliably save you money unless you give us up-to-date information about your electricity tariff. Head to "Smart tab > Your tariff" and update your tariff details there.

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