Abstract: A field expandable modular housing system includes a plurality of housings having a universal configuration, with each housing including a fan box for securing a predetermined cooling fan, air inlet and exhaust ports, front and back doors, a cable trough mounted near the top of the housing, and side cutouts for permitting electrical cable to run between bolted together ones of the housings, for electrically interconnecting electrical equipment contained within the housing, and universal equipment mounting brackets installed within each housing for securing desired equipment within each housing.