I have installed at least 100 of these professionally and have had 100% success. Some are several years old and are still working You can test them by placing it in the freezer with the sensor in a cup of water and the power cord plugged into an extension cord. Use a light (outside of the freezer) plugged into the thermostat. There is a time delay so be patient. When the light turns on your good to go.

I bought 4, and one failed in less than one season. I installed all 4 next to one another under the eaves, so they all are exposed to the same temperature. I installed the water sensors side by side in the bottom of my gutters. I noticed that the one doesn't turn on when it's below freezing and all of the others are on. This odd-ball turns on when it's much warmer and the other 3 are off. I believe the thermostat is bad in the one unit, but for $75 it should work for more than a month or two.

I don't know if I am just unclear as to how this is supposed to work, but no matter how frigid out, no matter how much snow was covering the sensor cable, this never turned on, thus the cables never warmed. After two days of messing with it, I gave up and plugged the deicing cable directly into an outdoor extension cord, and into the plug. It's not as efficient as I had hoped, but you gotta do what you gotta do.

I bought two of these to control de-icing cables on both sides of my house. When they work, they work well, saving energy by only turning on the heat cables when the conditions are favorable to do so. However, I've had one unit fail after one season, and I'm pretty disappointed about it. For the cost, they should last longer than just one winter.

I bought this along with 160 feet of the easyheat cable. I installed it and that very night we had a small storm. It started off as ice and turned to snow. I went outside and looked at this unit and the light was on indicating that it had activated. I went and looked an hour later and the light was off. The snow continued to fall the rest of the evening. When I woke up the next morning, The cable had never come on again. I cannot return it since I bought it last year but I did not install it until this year. Wasted my money. So, what I did, I bypassed this unit and plugged it into a smart outlet. I now turn it on and off with my phone. I can even schedule it, or set a timer for it once I turn it on.I just can't forget to turn it on!