A main switch at the back of the unit is always set to "On". But in principle, the machine is then in sleep mode and hardly needs any energy.
When you want a coffee, the machine wakes up. After a warm-up phase (which can also be selected slower or faster, corresponding to less or more energy consumption), the coffee is dispensed. THEN: How long it takes for the machine to go back to sleep mode can be SELECTED; I think from 15min to 3 hours (well described in the manual). As a rule, 15 minutes is good, because the warm-up phase is quite short. It is hardly annoying. The machine is great! Everyone is immediately familiar with it, cleaning is easy and the coffee is very good. In addition, you can adjust everything; grind, amount of coffee and even brewing temperature. Best regards!

Yes, you can programme time intervals; this is well described in the operating instructions.