Find a company near you to repair or replace your thermostat. Better Homes & Gardens Local Services connects you to companies that specialize in thermostats. Get started on your thermostat installation with a free quote!
The purpose of a home thermostat is to maintain the indoor air temperature at a desired target level, called a "setpoint." Thermostats achieve this by: monitoring the home's temperature with a sensor, turning your heating/cooling system ON when the temperature moves too far away from the setpoint, and, turning the heating/cooling system OFF once the desired temperature is restored.
In central air and some other kinds of systems, the thermostat may also control the fan, allowing filtered air to circulate even if the heating or cooling system is idle.
Digital thermostats combine standard thermostat capabilities with programming capabilities, so homeowners can program different target temperatures by time of day, and day of week.
So-called " smart thermostats" – coupled with home automation systems – offer functionality similar to digital thermostats, plus additional features like: sensors that can determine home occupancy patterns, remote operation from computers and mobile phones, alerts when issues occur, like an air filter that need changing.
In some "smart" systems, the home is divided into "zones," with a thermostat placed in each zone (or room). This helps avoid wasting energy at times of the day when only a few rooms are in use.
"How do thermostats work?"
Thermostats are basically comprised of: a sensor (or thermometer in older models) to determine the indoor temperature, a switch that activates heating or cooling, and, a control device, typically mounted on a wall.
Older thermostats made use of mercury thermometers to determine room temperatures. Newer digital thermostats use a metal resistor called a thermistor, or other semiconductor devices, in order to determine temperatures.
If room temperature readings stray too far from target settings, a switch is activated to initiate the system's heating or cooling mechanism. Once the temperature returns to the desired setting, the switch reactivates, this time to stop the heating/cooling mechanism.
It's worth noting that thermostats also have different electrical characteristics, depending on the system:
Low voltage thermostats – which operate around 24V – are used in central AC systems and most other contemporary HVAC systems.
Line voltage thermostats – which operate between 120V-240V – are mainly used with electrically-driven systems like electric furnaces, baseboard heaters, electrical radiant heat and space heaters. These kinds of systems require considerably more energy to operate than low voltage systems, and are thus declining in popularity.
"What are the most common thermostat problems?"
Diagnosing a heating or cooling system issue isn't always easy. Once you've checked for common causes like clogged air filters, water leakage from malfunctioning pumps or dislodged hoses, or tripped breakers, it might be time to consider the thermostat.
Common thermostat-problem symptoms include:room temperatures are too hot or too cold, unusual or extreme temperature swings, the system is cycling on and off too frequently.
Common causes you can fix yourself include: a weak battery in the thermostat control panel, dust and dirt inside the thermostat.
Common causes that generally require an HVAC professional include: the thermostat is old and failing (in some cases DIY'ers can fix this), inaccurate temperature readings by the sensor, the thermostat is placed too near a heat or cooling source that's not indicative of the entire home's average temperature.
Consult with an HVAC professional or you can't easily solve the problem yourself.
"How often should thermostats be replaced?"
Thermostats can last over 20 years, but regardless of age, if your thermostat is consistently malfunctioning or not giving you accurate control of your room temperatures, it’s probably time to replace it.
Homeowners also replace thermostats to get upgraded models with additional features.
It's a good idea to get a professional's opinion on whether or not to replace your thermostat, especially since most thermostat replacements are done by HVAC pros. Aside from pros having the knowledge of exactly what to do, they can advise on the best new thermostat options for your current HVAC system and household needs.
"What is a smart thermostat?"
Smart thermostats offer the most advanced features for managing and controlling room temperatures. These devices can learn from your living habits, and schedule heating or cooling accordingly. In "zone" systems, they can even control temperatures by room or area of the home.
While more expensive, smart thermostats offer a variety of special features including energy efficiency to save money, Wi-Fi access to control thermostat settings from anywhere, and voice control.
Smart thermostats can be installed in line voltage or low voltage systems.