19.—(1) Subject to article 23, the cost score for a heating qualifying action notified under article 17 is calculated—
(a)except where sub-paragraph (b) or (c) applies and subject to paragraph (2), by determining the cost saving for the qualifying action in accordance with—
(i)the Standard Assessment Procedure or the Reduced Data Standard Assessment Procedure; or
(ii)an appropriate methodology approved by the Administrator under article 24;
(b)in the case of the repair or replacement of a qualifying boiler, in accordance with article 20 or article 21, as applicable; or
(c)in the case of the repair of a qualifying electric storage heater or the replacement of a qualifying electric storage heater by another electric storage heater, in accordance with article 22.
(2) Where paragraph (1)(a) applies in respect of a qualifying action installed in Scotland, the cost score for that action may also be calculated by determining the cost saving in accordance with SAP 2009.
(3) Where a qualifying action is the installation of solid wall insulation which is accompanied by an appropriate warranty, the expected lifetime of the solid wall insulation, for the purpose of calculating its cost score, is 36 years.
(4) In paragraph (3), “appropriate warranty” has the meaning given in article 18.