Energy or EU (abbreviation of Energy Units), is a gatherable resource in Hawken. The EU Tank size of a mech is determined by its class. A-Class mechs can hold up to 150 EU, B-Class mechs can hold up to 200 EU, and C-Class Mechs can hold up to 250 EU. In Siege, EU is used to fuel up the team's battleship in order for it to launch. When mechs die, they drop any EU they were carrying, which can be picked up by other players. In Co-op Bot Destruction, EU is used to upgrade the player's mech. In this mode, EU is dropped from destroyed bots.