The rating standards for compressor and condensing unit performance data assume publication of data representative for the average produced units. The tolerance allowed according to the AHRI and EN standards is regularly reconsidered during revisions. These standards do contain descriptions of the rating conditions and associated tolerance values. The tolerance values in AHRI 510, AHRI 520, AHRI 540, AHRI 570, EN 12900 and EN 13215 are varying with the rating conditions and are considered necessary with the present state of USA and European production and testing standards.