Efficiency means minimizing the use of the costliest components. It's installing fault points into a system on purpose. Robust systems minimize fault points. E

Efficiency means minimizing the use of the costliest components. It's installing fault points into a system on purpose. Robust systems minimize fault points. Efficient systems come at the cost of robustness, and vice versa given a fixed definition of what is being conserved, i.e. costs or energy. For example, a four cylinder engine that gets 15mpg will have a longer life than one that gets 30mpg, given the same cost.