To eliminate photo degradation, we have proposed the elevation of the operating temperature of amorphous silicon modules by thermal insulators (polystylene foam) attached to them. A solar cell which degraded 19% with ordinary accelerated test condition (AM 1.5, 1 kW/m(2), 48 degrees C, 550 h) degraded only 13% at 90 degrees C. The temperature coefficient of amorphous silicon solar cell is about 2/3 of that of crystalline silicon solar cells. A simple calculation predicts about 80% of the initial efficiency in actual operation. Modules whose initial efficiency is about 9.2% were field on 1 April 1996. These modules showed more than 8% effective efficiencies on 21 August 1996. The cell temperature elevation by thermal insulation depends not on the ambient temperature but on insolation and wind speed, and is about 8 degrees C on average and 40 degrees C at peak. Effective conversion enhancement by temperature elevation is about 1% of the conventional one, which can be larger in later observation.