220 ILCS 5/3-115

"Service" is used in its broadest and most inclusive sense, and includes not only the use or accommodation afforded consumers or patrons, but also any product or commodity furnished by any public utility and the plant, equipment, apparatus, appliances, property and facilities employed by, or in connection with, any public utility in performing any service or in furnishing any product or commodity and devoted to the purposes in which such public utility is engaged and to the use and accommodation of the public.