Your actual savings will vary due to many different factors including: installation location, shading, air duct leakage, air handler location, geographic location, etc.  In the South, you can expect to see a 40% reduction in heat gained through the roof, and this can translate into a 17% savings on cooling costs. Many independent studies and radiant barrier users have tested their results and reported energy savings varying from as low as 12% up to as high as 39%.  Ra-flect™ radiant barrier reduces energy costs in both summer months and winter months because it is double sided, and will keep heat in during the winter months and reflect radiant heat away during the summer. Installing a radiant barrier in your attic is the most cost effective way of reducing your heating and cooling cost and providing the quickest payback of any energy efficient material or product.