(1) Subject to such conditions as the Commissioners may prescribe or otherwise impose, a full relief from tax shall be granted on any solid fuel that is shown to the satisfaction of the Commissioners to have been delivered for use -

(a) solely for the generation of electricity,

(b) for chemical reduction or in electrolytic or metallurgical processes,

(c) under diplomatic arrangements in the State, or

(d) for heat and power cogeneration (other than heat and power cogeneration by a micro-cogeneration unit within the meaning of Directive 2012/27/EU of the European Parliament and of the Council of 25 October 2012 [OJ No. L315, 14.11.2012, p.1]), where it is determined, by a competent authority designated for the purpose by the Minister for Finance, that such cogeneration meets the requirements for high-efficiency cogeneration under Directive 2012/27/EU of the European Parliament and of the Council of 25 October 2012.

(1A) The relief under subsection (1)(d) shall be calculated as the amount of tax paid on that portion of the solid fuel used for cogeneration that is used to generate high-efficiency electricity as determined, and set out in a certificate issued, by the competent authority.