Translation of "efisien" into English

Menurut Anda, pendingin ruangan apa yang paling efisien?

Which air conditioner do you think is the most efficient?

Tidak perlu, tapi saya meyakinkan Anda bahwa ia sangat efisien.

Nor should you, but I assure you he's highly effective.

Mereka ingin masyarakatnya terorganisasi dengan baik —seperti sistem kereta kuda mereka yang efisien dan begitu tepat waktu.

They wanted their society to be well organized —like their efficient stagecoach system that ran so punctually.