Ecostat Mercury-free 1 Heat/1 Cool Non-programmable Round Thermostat, Large Easy to Use Mode Switches

Really liked the simplicity. Just what I wanted. Gravely disappointed to discover this thermostat has no temperature hysteresis. What that means is once the room gets to the set temperature, the furnace can cycle frequently; off for the minimum selected 5 minutes, on for only a few seconds, maybe minutes, then turn off again. One time, heard the furnace fan come on for about 10 seconds, then go off.Once the thermostat tells the gas furnace to turn on, it takes about 15 seconds for the firebox to heat up enough for the fan to start running. The house is 40 years old and does not have insulated ducts, so once the fan turns on, typically takes another 15-20 seconds for the warm air to be felt at the room registers. That means there was at least 15 seconds of wasted energy that had no heating affect on the house. Even if the furnace runs for a full minute before turning off, that is only 50% efficiency.