Munter2, you got it wrong. When the phone is in battery saver mode, it uses more power than in normal mode. Or lets put it other ways - the more services are running the less it uses battery. Kinda crazy but true
For example, i have 21% power left, from the last chare 26h, meanwhile, I have made several calls watched ca 1h videos, used e-mail, internet, facebook, surfed web, BT, wifi etc turned on. But if I have had turned several services off and done nothing that then there would not be more juice left in the phone.