A key feature of energy is that it’s a calculated quantity, and that there are many possible calculations to work out the energy shifted.
Machines are designed to make tasks easier, but there is always a trade-off: you can’t get something for nothing.
Machines are often used as an introduction to energy, and this idea of a trade-off can be exploited and carried over.
Weight and height are two compensated quantities — there is a trade-off between weight and height in shifting a quantity of energy.
Filling a kinetic store has different trade-offs.
As do others…
Power in the electrical pathway is calculated from two compensated quantities: current and voltage.
Again, because it makes physical sense to compare powers, this is a natural fit for reasoning with boxes. An example: two circuits differing in current & potential difference, but switching the same power.