The Electric Furnace is an improved version of the Iron Furnace from IndustrialCraft2. It is 12.5% faster and, as the name indicates, uses electricity in the form of EU. By running on electricity instead of burning items, it is able to shut off immediately upon finishing (and thus avoid wasting energy). You can best take advantage of this by having some form of energy storage between the Electric Furnace and the generator(s).
The Electric Furnace can receive up to 32 EU/p (Low voltage packets), unless it is upgraded with a Transformer Upgrade. If you supply it with any more energy than low voltage (32 EU/p) without a transformer upgrade, the Electric Furnace will explode! Each transformer upgrade enables one higher tier of power. From baseline 32->128->512. 512 meaning with two transformer upgrades you can plug it directly into a MFSU; ideal when you have the other slots filled with overclocker upgrades. The Electric Furnace consumes approximately 390 EU per operation and requires a minimum of 3 EU/t to operate continuously. With 12 overclock upgrades this will consume the full 512 EU/t flow of an MFSU. This for example would mean you need an MFSU for each fully upgraded furnace for full performance. It also has a small internal power storage.