"HeatTrak says its stair mats willprevent snow and ice buildup during a 2-inch-per-hour snowfall. Up to 10 mats can be connected to oneanother (in a parallel circuit) and plugged into a standard 120-volt outlet. More mats require a second power cord. Control options include a plug-in temperature sensor, a hard-wire snow sensor, and an outlet switch inside the entry door. The company also makes walkway mats."