A systematic investigation has been made on output measurement of the a-Si//al-SiGe//a-SiGe triple stacked solar cells. Prototype modules incorporating triple a-Si cells fabricated in high deposition rate plasma CVD process with micro-wave power source[l] have been exposed outdoor for about a half to one year at three different geographical locations to evaluate the outdoor performance under cold, temperate and tropical climates. The results showed that a-Si performed better under higher temperature climate. Energy efficiency over 8% was obtained in Kuala Lumpur. Power rating under 1 sun, 50deg.C light soaking condition seems to be reasonable in Kyoto.