create an adder when the device is off

hi! please excuse me for my bad english
I want to make energy for my game. I want that : after each level the energy decrease one… But this is my main question: how can I create an Adder in my game that increase the energy number every five minutes when the game is close??? (in Android Device)

Thank you…
But I saw that many games have it … !!? NO WAY ???