21.—(1) Subject to the following provisions of this Article, the prices to be charged by a public electricity supplier for the supply of electricity by him under Article 19(1) shall be in accordance with such tariffs (which, subject to any condition included in his licence, may relate to the supply of electricity in different areas, cases and circumstances) as may be fixed by him.
(2) A tariff fixed by a public electricity supplier under paragraph (1)—
(a)shall be so framed as to show the methods by which and the principles on which the charges are to be made as well as the prices which are to be charged; and
(b)shall be published in such manner as in the opinion of the supplier will secure adequate publicity for it.
(3) A tariff fixed by a public electricity supplier under paragraph (1) may include—
(a)a standing charge in addition to the charge for the actual electricity supplied;
(b)a charge in respect of the availability of a supply of electricity; and
(c)a rent or other charge in respect of any electricity meter or electrical plant provided by the supplier;
and such a charge as is mentioned in sub-paragraph (b) may vary according to the extent to which the supply is taken up.
(4) In fixing tariffs under paragraph (1), a public electricity supplier shall not show undue preference to any person or class of persons, and shall not exercise any undue discrimination against any person or class of persons.