Which characteristic of a computer refers to its ability to minimize energy, consumption and resource usage?

Computers are often described using a set of standard characteristics: speed, how fast operations are carried out; versatility, the ability to perform many different kinds of tasks; reliability, the ability to produce consistent, error-free results over time; and efficiency, how well the computer uses the resources available to it.

Efficiency is specifically about getting the required output while minimising waste, whether that waste is electrical energy, processing power, memory, or storage space. A computer described as efficient is one that completes its tasks using as little energy and as few resources as necessary, rather than one that is simply fast or dependable. Speed, versatility, and reliability each describe a different quality of performance, but none of them refers to minimising the resources or energy consumed while working.

When a question mentions minimising consumption or resource usage specifically, that wording is the signal pointing to efficiency rather than to speed or reliability.