Mirror defoggers have been found in Asian and European hotels and residences for years. In fact, it's more common than not in a lot of areas. It is only now starting to become popular with Westerners. While there are many types, the basics are all the same, combine voltage and resistance and you 'll get heat. It is what material that is used to get the resistance is what separates the different types of defoggers.
SEARCLEAR's defoggers are made with a very reliable small resistive wire which is sandwiched between an adhesive backed pad.
The SEACLEAR mirror defogger is a thin electrical heating pad that adheres to back of a mirror which will prevent condensation from building up on the mirror surface. The defogger can be simply wired into the bathroom light or fan. Available in rectangle, oval or round shapes in 12, 24, 120, 220 volts.
The sizing of the correct defogger is directly related to the size of your mirror. While you can defog the entire mirror, the defogger should be not be less than 60% of the mirror size.