How do I calculate ship supply usage?

[MegaTrain]

When looking at individual components, they usually have a "supply usage" value, like engines are 10, cloaking device is 100.

But how does this translate to actual usage? Certainly it's not 10 * 6 engines = 60 plus 100 (cloak)=160 per turn, that seems WAY too little.

Is it 10 * 6 engines * 7 movement = 420 + 100 = 520 per turn. That STILL seems small.

Bottom line: I need to know how many Solar Collectors to put on a scout ship to make it self-sustaining.

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-MegaTrain-
Athlon 1.3 GHz running at 1.6 GHz on an iWill KK266