Single Stage Non Programmable Mechanical Thermostats

There are 2 types of heating and cooling systems: multi stage and single stage.  A single stage thermostat can only tell a multi-stage device (ex: furnace) that it requires heating (or cooling) while a multi stage thermostat can also tell the system how much heating or cooling it wants. 

If you're on a budget or just looking for a hassle-free way to control your temperature, consider a single stage nonprogrammable mechanical thermostat.