There's no one-size-fits-all answer, but generally, calibrating your thermostat once a year is a good rule of thumb. This can be done by a professional as part of your regular HVAC maintenance routine. Whenever you change the batteries in your thermostat, it's also wise to check its calibration.
Turn the screw to match the temperature of the thermostat to the room temperature. Turn the HVAC system and the power back on, and the power. Turn on the thermostat and wait a few minutes for it to adjust to the temperature.
Leave both units in place for another 20 minutes, and check the readings again to see if the readings are the same. If the readings between your thermostat and thermometer are still different, you likely have a malfunctioning thermostat and there may be an issue impacting thermostat accuracy and efficiency.
They must also be calibrated after an extreme temperature change (e.g., after measuring a hot food first and then a frozen food, or after a thermometer is dropped). All calibrated thermometers should be accurate within 2 degrees (plus or minus 2 degrees).
To do so, locate your home's thermostat and tape an accurate thermometer on the wall next to it. Wait 15 minutes and check the temperature reading on both devices. If your readings are three or fewer degrees apart, you should be good to go.
Battery Check. A common oversight for a thermostat showing the wrong temperature is the state of its batteries. Dead or low-power batteries can lead to inaccurate readings. Simply replacing the batteries might restore your thermostat's accuracy and functionality.
If the temperature is set to 74°F but the thermometer shows 78°F, you will have to recalibrate the thermostat to account for this 4-degree deviation. Even with older AC units or furnaces, you might have to recalibrate your thermostat from time to time.
Incorrect temperature readings can lead to undercooked food, increasing the risk of foodborne illnesses. Regular calibration of your food thermometer is the best way to maintain its accuracy. It helps you avoid the pitfalls of undercooking or overcooking, ensuring your meals are both delicious and safe.
Add pre-chilled water to just below the top of the ice. Stir for about 15 seconds. Insert the thermometer stem or probe 2″ into the center of the ice bath and stir gently for another 15 seconds, keeping the stem surrounded by the ice cubes and moving constantly. An accurate thermometer will read 32°F.
Dirty or worn flame sensors, blower motor problems, clogs in the condensate lines, and electrical issues are some of the many problems that can leave your HVAC system failing to deliver the temperatures you've programmed in your thermostat.
One easy thing you can do to check the accuracy of your thermostat is to do a temperature check. See what your thermostat reads. Then use a portable indoor thermometer to compare the temps. Another good way to do the temperature check is to download one of the many free apps that allow you to check indoor temperatures.
When you set the thermostat above or below the current room temperature, you should hear a click, and the AC or furnace should kick on almost immediately. If you make changes at the thermostat and nothing happens, that's the first sign you have a bad thermostat.
Using a soft brush or a can of compressed air, carefully clean the sensor to remove any dust or debris that may have accumulated on its surface. Be gentle to avoid damaging the sensor. Once the sensor is clean, reattach the thermostat cover and restore power to the thermostat by flipping the circuit breaker back on.
Some of the most common thermostat issues include:
The thermostat is broken, not properly level, or dusty. The thermostat needs to be recalibrated. There is loose wiring causing a thermostat issue. The thermostat is not in an ideal location in your home.
The calibration screw is typically located in a curved piece of metal. First, remove the control unit from the wall mounting and then locate the screw in the back. Turning it back and forth opens the contacts. Once you feel the setting is correct, turn the calibration screw again to close the contacts.
Direct sunlight, cold temperatures or a sweaty forehead can affect temperature readings. Variations on user technique, such as holding the scanner too far away from the forehead, also may affect accuracy.
Failure to calibrate equipment can lead to a cascade of operational inefficiencies. Inaccurate measurements can cause machinery to operate under suboptimal conditions, leading to increased wear and tear. This not only shortens the lifespan of equipment but also escalates maintenance costs and downtime.
There are two main types of thermometers. The dial or bi-metallic stem thermometer and the digital or instant read thermometer. The bi-metallic stem thermometer is a mechanical thermometer which must be calibrated regularly. A digital or instant read thermometer is electronic and cannot normally be calibrated.
Over time, the components of your equipment can drift or wear, leading to measurement errors that can compromise the quality of your work. For example, if you are using a thermometer that has not been calibrated, it may provide inaccurate temperature readings, which could result in incorrect conclusions or decisions.
For many of us, 70 degrees is the ideal indoor temperature, but when it is close to 100 degrees outside, your AC unit will be working quite hard to meet these expectations. Consider setting your thermostat at 75 degrees to 80 degrees in your home if the outside temperature is approaching triple digits.
Another problem that can cause your house to be hotter than what you've set the thermostat to is if your home's HVAC system isn't sized properly. An HVAC system that's too large for your house will cool your home unevenly. It will only cool some rooms off and then shut off versus cooling down the entire house.
Your AC might not cool properly due to thermostat issues, an undersized unit, or extremely high outdoor temps—so check those first. Keep an eye on airflow—replace clogged filters every 3 months, and make sure vents and ducts aren't blocked for efficient cooling.