耗能

dī hào néng dēng

低耗能灯

low-consumption light

zhè xiē shén qí de fā dòng jī gōng zuò shí bìng fēi wán quán bù hào néng

这些神奇的发动机工作时并非完全不耗能。

The energy from these remarkable engines is not entirely free.