Quick Summary: Why is SHGC more important than U-Factor in California? When looking for energy efficient windows, California homeowners should focus on Solar Heat Gain Coefficient (SHGC) as the critical metric. While U-Factor (insulation) is vital in freezing climates, a low SHGC rating is essential for Orange County homeowners to reduce cooling costs by up to 40%  during long, sunny summers.   Understanding the NFRC Label: The Blanket vs. The Sunglasses When shopping for   h