How does the energy consumption calculation work?

The view for energy consumption shows a calculated annual consumption. It is not a log over consumed energy.
The idea with the view is to give you the chance to lower your bill by, in advance, knowing how many kWh a device will be on with the current schedule setup.

If you have a device with the effect of 100W that is always on between 08:00 and 10:00, the annual consumption for the device is 73kWh. If you adjust the schedule so that the device is only to be on between 08:00 and 09:00, the consumed energy will be reduced and this will be visible in the view.

When the energy consumption calculation is carried out for devices connected to a schedule that is bound to rules, the "maximum time" for the device is calculated - i.e. the total consumption for the device for one year if all rules are fulfilled all the time.