The MFE is a second tier EU Storage unit, that stores 600,000 EU, rather than 40,000 of the Batbox. It accepts up to 128EU/t of power, and will output up to that value from its 1 output face. It has 5 input faces that can be used. In order to use the MFE with basic machines without upgrades, you must have an LV-Transformer connected to the output face or the cable will overload and explode, possibly resulting in the destruction of the machines or the MFE unit.
It is used in crafting the MFSU, a higher tier EU Storage unit.
The MFE is suitable for most medium-size setups and for small Nuclear Reactor setups, but it will quickly be filled by the longevity of the Uranium Cells.
It requires a bit of resources to make, as it needs 4 Diamonds and 32 Redstone to make the 4 Energy Crystals. A Machine Block and 4 2xInsulated Gold Cable are also needed.