When evaluating solar fans, prioritize the Battery Capacity (mAh) and Solar Panel Wattage (W). For reliable performance, look for Lithium Iron Phosphate (LiFePO4) batteries, which offer over 2,000 charge cycles compared to standard Lead-Acid batteries. Ensure the solar panel is Monocrystalline Silicon for higher conversion efficiency (up to 22%). Additionally, verify the CFM (Cubic Feet per Minute) rating to ensure the airflow meets the intended usage scenario, whether for personal cooling or industrial ventilation.