Power throughout Indonesia is 220 to 240 Volts AC. Power outages can be frequent during the rainy season. Power plugs are recessed receptacles taking two round prongs. Bring an adapter with you.
Note that most electronic devices, such as MP3 players, digital cameras and notebook computers have adapters that will take any voltage from 100 to 240 volts. You generally don't need a power converter, you just need an adapter for the plug.