There are two major benefits recognized from using insulated curtains. First, insulated curtains help control room temperature. These curtains add an extra layer of protection over your windows -- which are almost always the leading source of heat loss or exchange in your home -- by increasing the R-value of your window [source: Solar Components]. During the warm summer months, these window coverings will block out the sun's heat, so you can use less air conditioning. Then in the winter, they help hold heat in the house, allowing you to turn that thermostat down. Since cooling and electric heat are big contributors to a household's overall electric bill, the benefits from cutting down on how much you need to use them can be significant.
Second, insulated curtains help soundproof a room. Not only will they keep noises from your yard out, but they'll keep your noises in. You'll still need to be considerate of your neighbors when blasting the stereo, but the curtain will alleviate some of that noise. The thick curtains absorb sound waves, keeping them from vibrating into your home and ears, or vice versa.
For even more helpful information on insulated curtains, be sure to check out the links on the next page.