The bitter cold temperatures are upon us, and so, it is vital to ensure that your furnace is working effectively. With a high number of service calls regarding dysfunctional furnaces, what many homeowners are not aware of is the impact of thermostat batteries on the performance of your furnace (and air conditioner) unit. Most models will warn homeowners of dying batteries - usually by flashing a low battery symbol on the face of the thermostat, however, it can be easy to miss. Settings (time, date, preferred temperature, etc) may be lost when batteries are very low. This will result in the need to reprogram the thermostat. A good rule of thumb is to change the thermostat batteries once a year to prevent such issues from arising.