The advantages...

Heat Mats on a Windscreen

Windscreens become "frosted" because of condensation on both surfaces, inside and out. When the temperature is low enough, the moisture on one or both of these surfaces freezes and becomes difficult to remove.
Statistics prove that a huge number of accidents happen during the period when it would be expected that windscreens have not had time to clear.

Heat Mats are faster...
Scraping away at your car windows can take up to 10 minutes depending on the severity of the frost. Heat Mats act far more quickly, and can clear most of the frosted or frozen surfaces on your entire car in a few minutes. They take seconds to apply, and while you are waiting for the first one to take effect, you can apply the other three in your set. Defrosting sprays are very ineffective, and generally do not provide a fast or suitable solution.

Heat Mats are better...
Heat Mats transfer their heat to the Window or surface you place them on. This means that they dont just remove the ice, snow or frost, but they also help to prevent condensation inside the car. This means that when you get in your car, your breath wont steam up the windows, which is good, as steamed up windows can be just as dangerous and difficult to combat as frost can be.
Heat Mats are also the only defrosting method that warm your hands while you defrost, and result in a much clearer window.

Heat Mats are safer...
It is no longer safe to leave your car unlocked, running and defrosting outside your own house. Theives see this period of the morning as an easy opportunity and will often take advantage of the fact that many cars will be ready to drive away.
Heat Mats also defrost your windscreen without the risk of damage, as the heat is dispersed over a wider area, and absorbed over a longer period of time. Pouring boiling water from a kettle can risk cracking your windows.

Heat Mats are car and environmentally friendly...
Defrosting sprays are polluting and can rot the wiper blades. Pouring a kettle of boiling water may defrost your windscreen, but it usually results in a patch of ice on the ground, which is dangerous to yourself and other people.

Heat Mats are cost effective...
Four sets of heat mats lasted for a two year test during which 11 cars were driven in freezing conditions many hundreds of times each. This is many times more effective than defrosting sprays, resulting in a very large saving (as the spray cans cannot be refilled).