We investigated the unevenness of, and change in, the characteristics of CIS-type thin-film solar modules during a 6-month storage period. The maximum output power (P-max) improved by an average of 1.72% in that time. This improvement was attributable mainly to the increase in shortcircuit Current (I-sc) which was about 5.9% after 6 months. The change ill P-max also depended oil the change in the fill factor (FF); the correlation coefficient between P-max and FF was 0.68. Finally, as P-max was the main factor in module performance, its change also depended oil both the value of, and change in, series resistance over time. (c) 2006 Published by Elsevier B.V.