Increase energy output of a cubic metre lava

Since 1.3.2 you can put lava bucket of lava in cobblestone furnances and you will gain the bucket back. So a stone furnances can smelt 100 units whereas a more modern iron furnances can smelt only 12,5 units.Here you can see it even in the wiki
http://wiki.industrial-craft.net/index.php?title=Electro_Furnace.