1. The California Energy Commission (CEC) efficiency is for climates of higher irradiation intensity corresponding to California climate like US south-west regions. It is a weighted efficiency, which obtained by assigning a percentage of time the inverter resides in a given operating range.
2. CEC efficiency are weighted efficiencies. In calculating them, the efficiency of an inverter at different spots within the operating range are taken into consideration and ‘balanced’ against each other depending on importance. For thevCEC efficiency, there are 6 efficiency points in the calculation.
CEC Eff = 0.04 x Eff10% + 0.05 x Eff20% + 0.12 x Eff30% + 0.21 x Eff50% + 0.53 x Eff75%. + 0.05 x Eff100%
http://files.pvsyst.com/help/inverter_euroeff.htm (1.); http://www.solarselections.co.uk/blog/types-of-solar-inverter-efficiency-peak-vs-euro (2.)
Author: Laura Saupe