When winter hits and you turn on your heat, your furnace kicks on. You turn on your heat with the thermostat and your furnace cranks out heat until the room temp reaches the set temp. Then the thermostat turns off the furnace. This cycle of on/off with the furnace continues until you turn the furnace off for the summer. If your thermostat breaks, the furnace will just keep running, overheating the house, until the furnace breaks as well. THIS IS HOW YOUR SNAKE HEATING WORKS AS WELL. You plug your heat mat into a thermostat to set and regulate the temperature of the heat mat. You verify the temperature with a thermometer where the snake will be laying over the heat mat. The thermostat keeps turning the mat on and off to stay within range of the set heat. If you don't use a thermostat, the heat mat just stays on all the time, climbing as high as it will go, until it dies. If the temps go high enough, you could seriously harm or even kill your snake. If your room temps stay above 85, you can unplug the heat mat to save on electricity. Just keep track of the temps with your thermometer, where the snake lays, to be sure it's at 85. If you have no AC, put a cold pack or frozen plastic bottle of water in the viv to cool the air for your snake. I hope this helps.