I think you need to compare to the other T3 furnaces, to see the differences in waste. I believe the T1 (basic) is considered the least efficient and slowest of all, so all of the T3 furnaces will out perform it.
I think you could just call this a bad use of words. The heat efficiency furnace will convert your material faster, and use the same amount of fuel as the lower tiered furnaces. The other T3 furnace (cant recall the name I havent smelted in a while) takes longer then the Heat efficiency furnace, but uses less fuel.
And FYI the furnace with the large chimney is as slow as hell.
The other one is so much faster, so unless you are totally deficient in gathering coal or making dry wood, use the fast one.
If you have access to coal, you can make around 10k hardened brick using about 400 coal or less with heat efficient furnace in about 30 minutes. If you don’t, use dryers to dry wood and use it.
If you completely don’t care about speed, use the fuel efficient furnace, log out, and log in 24 hours later for the same result. (you don’t have to go farm two nodes of coal)
Nothing else comes close to the speed of it. Two of these furnaces take up about a 2x 6 area of your base.
Just get kilns. Seriously, they give the best bang for buck. They have the smallest footprint and the second best fuel efficiency. Or at least, they used to in November, I don’t know if they fiddled with them since:
