The location of your thermostat affects your HVAC's (heating, ventilation and air conditioning) efficiency more than you think. This is because some areas of your house may be colder or hotter than your actual room temperature, and locating the thermostat in such areas will give false temperature readings. Here are some of those bad locations and why you should avoid them:
Skylights admit more light, and heat tends to accompany light from the sun, than other areas of the house. Therefore, if you install a thermostat near a skylight, it will be reading the temperature of the air just below the skylight, which is considerably higher than the ambient temperature of the rest of the room.
Near Air Vents
Air vents, both supply and return vents, also affect temperature readings. The main thing here is that you want the thermostat to read the temperature of the room so that it can adjust the AC and make you comfortable. This won't be the case if the thermostat is being affected by the draft from air vents.
Near Windows and Doors
In a typical house, areas near doors and windows have different temperature readings compared to the rest of the house. This makes these areas unsuitable for placing the thermostat. There are three main reasons for this; first, the draft will affect the thermostat every time you open the door or window. Secondly, the outside temperature will affect the thermostat when you open the windows and doors. Lastly, sunlight streaming through the windows and doors may also heat the thermostat.
Near the Kitchen
In most houses, the kitchen is the warmest room due to the high number of heat sources it houses. The cooking ranges and microwave ovens plus other cooking and electrical appliances all contribute to the temperature of the kitchen. Therefore, the kitchen's temperature is not something you should use as a baseline for cooling the house because its temperature will probably be higher than temperatures at different parts of the house.
Near Light Fixtures
Light fixtures, even those that look cool, emit some heat. Therefore, even after you have identified the perfect room for your thermostat installation you should ensure it is nowhere near a light fixture. Otherwise, you will just be relying on the heated air around the light fixtures to cool your house.
The best location for a thermostat is an inside wall somewhere central in the house. This is where you are more likely to get an average temperature of your house so that the thermostat can actually help keep you comfortable. Talk to an HVAC installation professional for more tips.