However, here are some options that convey a similar meaning:
* "Well-" as in well-organized, well-designed, well-functioning.
* "Wise-" as in wise use of resources, wise management.
* "Worth-" as in worthwhile, worth the effort.
The best choice will depend on the specific context.
For example:
* "This system is well-designed and very efficient."
* "The wise use of energy makes this a very efficient machine."
* "This method is worth the effort and extremely efficient."