The Electric Wrench is an electric tool powered by EU designed to replace the Wrench (IndustrialCraft 2). Since the Electric Wrench is an electric tool, it has no durability, instead it uses energy. The Electric Wrench can be used to pick up machines without the chance of breaking the machine.
You can switch modes with the electric wrench (default keybinds can be changed in the controls menu) by holding down the M key and right clicking. When you change modes in the chat window it should say Lossless Mode Enable/Disabled. When Lossless is enabled there is a 0% chance you will break the machine, though it uses much more EU. Lossless disabled uses very little power, and has the same chance to break a machine as a normal Wrench.