Not sure if this was an oversight or what, but it sucks through Coal like a furnace through string.

Why's it using so much fuel?

It has 25% efficiency - this means they burn fuel 4* faster than their energy output would suggest.. Thats just some "penalty" for not using/not having watter. You shouldn't use them unless you really must. Still it's cool imo that they exist.
I often make them in early game when my ores spawn far away from water.
In early game you don't need a lot of power, and you don't want to spend a lot of time and 200 iron on pipes going one way or transport belts with coal + power poles going another way

Ah ok, thanks.

I use them with The Dead Burn mod to supplement my power gen