To reduce photovoltaic (PV) power generation costs, the reduction of PV module manufacturing costs, the improvement of cell and module efficiencies, and the long-term output power warranty of PV modules are necessary. Using the high-quality, low-cost crystal growth technology, we developed a high-quality casting process by the seed-cast method. Using a seed-cast wafer, an efficiency of 20.54% has been obtained with passivated emitter and rear cells (PERCs). The ohmic contact degradation of front electrodes and potential-induced degradation are the typical modes that significantly affect the module lifetime. Considering the field stresses induced by ultraviolet light, heat and humidity (H&H), and the electrical potential difference, sequentially combined stress tests of small modules and additional stress tests of field-aged modules are performed. The test results for the modules fabricated using our technology indicated that the modules have a sufficiently long lifetime of more than 30 years and are potential-induced degradation (PID)-free under these stresses in Japanese domestic environments.