This expects to go on an electrical box. It has about a 5 degree hysteresis (gap in temperature between when it turns on and when it turns off), which surprised me at first...if you set it for 70F, you don't want it to heat the room to 75F before turning off! But in practice it works out just fine because you typically install it above your baseboard heater, and it heats up (from convection or even direct radiation) much faster than the rest of the room does...so when it reaches 75F, the rest of the room has only warmed a little bit and it maintains a pretty tight control.