I wanted to run my EBF from 4 lv diesel gens directly connected to the input hatches, but it didn't work. So I did some testing in creative after reading the relevant wiki page. Every eu outputting GT block has some loss depending on tier, it's 4 eu/t/amp for LV in this pack, including generators (wiki says 2 eu/t but that's wrong). I'm gonna assume you made a battery buffer and checked the batteries after 1 smelting. The minimum energy needed with 2 tin cables and a 4 times buffer is 170400 eu / operation. 60 (seconds) *20 (ticks) * 142 (eu/t needed =120 recipe cost + 4*4 block output loss + 2*1+2*2 cable loss). I don't know your setup but cable loss adds up quickly, 6 cables mean 22eu/t loss and a 189600 eu total cost.