A simple mean-field theory for the free energy of ice phases applicable to any of the widely used intermolecular potential models of water is proposed. The energetic effect of the hydrogen bond network is calculated via a set of self-consistent equations for the mean multipole moments of each molecule, which serve as the order parameters. An application to the TIP4P model of water yields results in good agreement with simulations, and produces a phase diagram in qualitative agreement with experiment. (C) 2003 American Institute of Physics.