I'm not sure if this is a bug or feature, as I would like it to work as a feature.

Anyway, thing is that you can set negative energy consumption values and a machine is producing energy.

I actually wanted to use this to make a workaround for the missing heat exchanger (put hot coolant into supercooler and get cold coolant + energy out).

It works that it fills up with energy, but I can't get the energy out of that machine. (Which is why I assume it's a bug).

I do like it to become a feature though, so you can then have cool setups, like the one I tried to accomplish.

Versions
NC: 2o.4.0-1.12.2
Forge: 14.23.5.2847

I tested pulling energy with thermal fluxducts and also with immersive engineering power lines.
Also only tested it with negative numbers in the config file for base power. I haven't tried crafttweaker recipes with negative power , as of now. But I am going to try that soon-ish.

It won't effect normal gameplay, but allow modpack makers more freedom.

Sorry for the very late reply, but this should be implemented in the next version of NCO for any custom machines which are defined as generators :)

Additionally, since your original comment, igentuman has actually added a whole bunch of machines to fill in for the currently missing heat exchanger mechanics, as well as having some other auxiliary uses, in his addon called Steam Additions.

This has been requested before - it's a bit tricky with the way machines are currently implemented, but at some point they may get a refactor and allow for stuff like this :)