Sometimes confused, they are different metrics although they are derived from similar data.
Utilisation refers to the extent to which a resource (such as a machine, labour, or time) is being used to produce a product or provide a service. It's a measure of how much of the available resource is being utilised.
Efficiency, on the other hand, is a measure of the extent to which resources are being used to achieve the best possible results with the least amount of waste.
In business, high utilisation and efficiency are important goals because they help to increase productivity, reduce costs, and improve the bottom line.
How are they Calculated
Utilisation can be calculated as a ratio of the actual resource usage against the maximum possible resource usage over a given time period. 
For example, if a garage has 4 ramps/bays but only has 3 technicians (who are productive 85.5 hours per week) however there are 160 hours available, then the utilisation would be 85.5/160 = 53.4%.
Efficiency can be calculated as a ratio of the output produced to the input used. 
For example, if a garage sells 60 hours of labour but the 3 technicians attended for 120 hours, the efficiency would be 60/120 = 50%. 
It's important to note that utilisation and efficiency are not always directly proportional, as high utilisation does not necessarily mean high efficiency. 
The concepts of utilisation and efficiency can also be applied to individual workers, but I prefer the term productivity to utilisation.
The example used can be found here https://docs.google.com/spreadsheets/d/1OVyjhk4e7_JUdhoTjtr9XmehC0C3H_3JaVMLVz1AviY/edit?usp=sharing

Ver todos los episodios