Window Energy Efficiency Comparison: Which Type Saves the Most?

Windows are the weakest thermal link in any home's building envelope. They account for 25–30% of residential heating and cooling energy use — more than walls, floors, or ceilings. Choosing the right window type for your climate can reduce energy costs by $200–$600 per year, while the wrong choice can actually increase bills despite being "new."

This guide compares every major window configuration using the three metrics that matter most: U-factor (insulation value), Solar Heat Gain Coefficient (SHGC), and the resulting annual energy savings by climate zone.

Before comparing products, you need to understand what the numbers mean: