Efficient
WordNet
adjective
(1) Able to accomplish a purpose; functioning effectively
"People who will do nothing unless they get something out of it for themselves are often highly effective persons..."-G.B.Shaw
"Effective personnel"
"An efficient secretary"
"The efficient cause of the revolution"
(2) Being effective without wasting time or effort or expense
"An efficient production manager"
"Efficient engines save gas"