  The distribution of local charge excesses (DLC) in metallic alloys,
previously obtained as a result of the analysis of order N electronic structure
calculations, is derived from a variational principle. A phenomenological
Charge Excess Functional (CEF) theory is obtained which is determined by three
concentration dependent, material specific, parameters that can be obtained
from {\it ab initio} calculations. The theory requires modest computational
efforts and reproduces with an excellent accuracy the DLC and the electrostatic
energies of ordered, substitutionally disordered or segregating metallic alloys
and, hence, can be considered an efficient approach alternative to conventional
electronic structure calculations. The substantial reduction of computing time
opens new perspectives for the understanding of metallic systems and their
mechanical properties.
