Upgrades are the most complex of the Tinkerer's Trinkets, and this is because they are parts that can be sort of magni-welded onto the mechanized suit that the War-Crafter pilots. As such the three tiers are more than tiers, they are also energy limits, which are all added together to be equal to or under the numeric cap to energy draw that the magni-mech can manage based on the War-Crafter's level.