The Stand-By graph uses smart learning algorithms to detect the total power usage of devices that are always on. The Stand-By graph can show you if you start using more or less power over time with dormant devices. Or can let you know if you left something was left on if it has suddenly spiked. The graph shows your regular Power Usage graph in the background, with an overlay of the detected Stand-By power level per period.

Standby graph is calculated once per day based on the data between 0:00 and 6:00. It then estimated based on the algorithms the total power consumed by devices that are always on and extrapolates this data to show how much power is being used by devices during the day.

The Stand-by graph is enabled automatically if you have signed up for Energy+ at Settings > Energy+.

Heres some examples of average stand-by usage per household type.

1 person apartment:

2 person apartment: ±50W continuous, 1.2kWh per day.

4 person house: ±100W continuous, 2.5kWh per day.

This can occur when you supply back with solar panels during the day, because your devices then use power from the solar panels instead of the grid. The standby use is still there, but is not taken from the grid. Another cause is that you have had devices on at night between 0:00 and 6:00, which are then switched off during the day.