[dirtball_]

I think you and the author may be in agreement on this topic.

Following your example of cars, having a large gas-guzzling full-size truck when you drive by yourself 5 miles to the supermarket once a week would indicate that the vehicle is being used at a low percentage of its capacity. If it were loaded up hauling heavy equipment and materials, to and from jobsites for example, then it would be near 100% capacity.

For the weekly grocery run, it is wasteful to have this truck since it is used at low capacity. One would be better served with a much smaller vehicle, even perhaps one that is human-powered (such as a bicycle).

"Ideally, the resource gets used at 100% of its capacity: we have enough capacity to serve our needs without generating queues, but not so much that we’re wasting money on idle resources."

The large (expensive) truck only used on the grocery run would be wasting money on idle resources, since it is capable of doing much more work but is rarely used.

[rightbyte]

Car decays by age but mainly by miles. Sooner or later the car will have reached 100% capacity even if just used once a week. Which I think is a good point against the "efficency" idiom.

Taxis are on the other end of the spectrum.