A question on heat of formation

Hi, CCLers!
 Should the heat of formations of two enantiomers of a chiral compound be
 identical? I think the answer is yes. Please point out some references
 for this.
 A disturbing fact is that, no matter you use QM or MM to calculate the
 heat of formation for a given molecule, the number is
 conformation-depentdent. I guess this is because of the steric energy
 part is conformation-dependent. So, if I really want to compare the
 stability of two molecules using heat of formation, how may I calculate
 it right?
 Best regards,
 Renxiao Wang
 renxiao(at)med.umich.edu