Caiff effeithlonrwydd ynni a pherfformiad amgylcheddol eu mesur gan y Weithdrefn Asesu Safonol (SAP). Yn gyffredinol, roedd sgôr SAP gyfartalog ar draws pob deiliadaeth yng Nghymru wedi cynyddu 11 pwynt SAP rhwng 2008 a 2017-18 i sgôr o 61, sy'n cyfateb i Fand D y Dystysgrif Perfformiad Ynni. Y sector rhentu preifat yng Nghymru a ddangosodd y cynnydd mwyaf, gyda chynnydd o 13 pwynt SAP.
Energy efficiency and environmental performance is measured by the Standard Assessment Procedure (SAP). Overall the average SAP rating across all housing tenures in Wales increased by 11 SAP points between 2008 – 2017-18 to 61, which is equivalent to an Energy Performance Certificate Band D. The private rented sector in Wales showed the biggest increase, with a rise of 13 SAP points.