The appropriate time to use emergency heat is during emergencies, such as when your heat pump isn’t functioning as it should. If you observe that your living space is cold as a result of damages to your heat pump, that is a clear indicator that you should make use of the emergency heat.
The heat pump is a piece of outdoor equipment. As such, it’s subject to damage from the elements and other factors. Therefore, you should check up on your pump regularly, especially during winter when snow and ice can accumulate on the unit. If your heat pump isn’t capable of providing heat, switch your thermostat to emergency heat and put in a call for professional service.