Using gmx energy in calculating free energy analysis

GROMACS version: 2018.8
GROMACS modification: Yes

Hello! I just want to ask if the option gmx energy can calculate the free energy of biomolecules? I just recently saw the documentation of gmx energy and it says that you need to add -fee and -fetemp. Will the obtained free energy values comparable with other existing free-energy calculation software like g_mmpbsa?

I hope you will help me with this matter. Thank you in advance.

Those options are not intended for biomolecules. They are used for neat liquids.