We have lived in northern Michigan, where it snows almost every day in the winter, for 15 years and just discovered the heat trak mats last winter (2010) What a blessing these heat mats have turned out to be !! I wish we had known about them sooner, as it would have saved a lot of shoveling over the years.
This particular review is for the 25' extension. You can hook up 5 mats to a controller (the cord that plugs into the outlet). Since our garage is detached from the house, and we also wanted to be able to access a shed, we needed 3 sets. We also wanted to have them all plug into outlets inside the house, so I can easily turn them off on warmer days (especially handy in the transitional fall and spring seasons). This also allows easy access to see if they are "on" when we know snow is coming (a small red light on the controller indicates they are "on"). We have discovered that it works best to have each set plugged into a different circuit. The 25' extension cord goes between the mats and the controller cord and allows us to configure the mats to meet our needs.