An inaccurate thermostat can cause your HVAC system to run too long, not long enough, or cycle on and off erratically, leading to uncomfortable temperatures and wasted energy. If you find yourself constantly adjusting the thermostat because the room feels warmer or cooler than the displayed temperature, your thermostat may be reading incorrectly. This is a common issue in New York City homes, especially with older mercury or mechanical thermostats that drift over time. Testing your thermostat accuracy is quick and easy, and it can explain mysterious comfort problems and high energy bills that no amount of other troubleshooting resolves.
Purchase or borrow a reliable digital thermometer, ideally one rated for room temperature measurement. Inexpensive indoor thermometers from hardware stores work well. Avoid using cooking or medical thermometers as they may not be accurate at room temperature ranges.
Tape or place the reference thermometer on the wall within 6 inches of the thermostat at the same height. Let both sit undisturbed for 15 minutes to equalize. Do not hold the thermometer in your hand as body heat will skew the reading.
After 15 minutes, compare the thermostat display to the reference thermometer. A difference of 1 degree is acceptable and normal. A difference of 2 degrees or more indicates the thermostat is inaccurate and may need recalibration or replacement.
Thermostat accuracy is affected by location. Check if your thermostat is near heat sources like direct sunlight, cooking appliances, lamps, or electronics. Also check if it is near drafts from windows or exterior doors. These factors cause false readings even in a working thermostat.
Some thermostats have a calibration screw or digital offset setting. Consult your manual for calibration instructions. If your thermostat is a mercury type or older digital model with no calibration option, replacement is the most practical solution. Modern digital thermostats are far more accurate.
If you want to upgrade to a smart thermostat that requires new wiring such as a C-wire, or if your thermostat controls multiple zones and needs professional calibration, call an HVAC technician for proper installation and setup.
Call (646) 439-4057A well-functioning thermostat should read within 1 degree of actual room temperature. Digital and smart thermostats are generally accurate to within 0.5 degrees. Older mechanical models can drift by 3 to 5 degrees.
Absolutely. A thermostat in direct sunlight, near a kitchen, above a heat register, or on an exterior wall will read inaccurately. The ideal location is an interior wall at 52 to 60 inches high, away from heat sources and drafts.
Fill out the form below and we'll get back to you within 1 hour during business hours.