In Turn based I moved a ship 1 space and the usage was 100. The total usage for the Warp Core (20) and 2 Nacelles (40 each) totals 100 as it should. After retrofitting it with 4 Bussard Collectors (5 each) and 2 Impulse engines (20 each) the usage for 1 space was still 100 (not 160).
Also it seems I edited my original message after you read it, you might want to reread it just in case (nothing important but I like the idea
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[edited to clarify usage amounts]