See how much new windows can save you — instantly. Upgrading windows is a big investment. Energy performance decides if it truly pays off. Most people see U-factor and SHGC and stop there. We built a tool that turns those numbers into money. Why we built a calculator Energy modeling is usually slow, expensive, or both. Many homeowners and builders simply guess instead. At the same time, ENERGY STAR windows can cut heating and cooling bills by around 10–15%. You can check the official ENERGY...