Press the start button and the car is in Ready mode = ready to be driven. There's no engine noise as it uses the electric battery to move off (usually). It's always in Ready mode when driving and swaps between petrol and electric power. By having it in Ready mode on the drive for an hour, the electric battery charges the 12v one. The petrol engine kicks in to top up the electric battery from time to time, but only stays on for a minute or two about 3 or 4 times. Every time you're at lights for example, the hybrid battery charges the 12v one so it's like an hour of being at the lights. You need to stay with the car of course (with no radio/ac etc. on), so best to be working in the garden or on a chair with a book.