What word means able to work properly while using less energy

it was given away at no charge

the use of “as” in the example to draw the resemblance. some more examples of common similes are given below. common examples of simile. our soldiers are as brave as lions. her cheeks are red like a rose. he is as funny as a monkey. the water well was as dry as a bone. he is as cunning as a fox. simile introduces vividness into what we say.