Maryland Code, Public Utilities § 4-503

(1) to the officers, employees, pensioners, and immediate family members of the officers, employees, and pensioners of a public service company;

(2) to the United States, the State, or a local government;

(3) to provide relief in cases of general epidemic, pestilence, flood, or other similar calamity;

(4) in the case of common carriers, to transport:

(5) in the case of common carriers, for the issuance of mileage, excursion, or commuter tickets;

(6) to free steamboat excursion transportation from May through August of each year, from Baltimore City to any place in the State, in exchange for services rendered in advertising the excursion business;

(7) to obtain essential data by a method that uses a limited sample of customers, in connection with a rate structure study conducted under formal proceedings before the Commission;

(8) to telephone lifeline service provided to eligible subscribers under § 8-201 of this article; or

(9) to electricity or gas service provided to eligible limited-income customers through an approved limited-income mechanism under § 4-308 of this title.

(1) charge, demand, or receive from a person compensation that is greater or less than from any other person under substantially similar circumstances;

(2) extend a privilege or facility to a person, except those privileges and facilities that are extended uniformly to all persons under substantially similar circumstances;

(3) discriminate against a person, locality, or particular class of service; or

(4) give undue or unreasonable preference to or cause undue or unreasonable prejudice to a person, locality, or particular class of service.