The majority of PTACs are manufactured with an electric heating element called a heat strip (see image to the right top). The heat strip is a wire heating element inside the PTAC that warms the air as it passes over the coils. This is very similar to what you would find in space heater.
A heat pump (right bottom) reverses the cooling cycle of the PTAC air conditioner. Refrigerant is used to heat the coils and the heated air is then pushed back into the room. A heat pump will run alone until the temperature reaches a certain point – usually below 35 degrees. Once it hits that threshold, the heat strip will take over and provide constant electric heat. This combination of heat pump/heat strip has proven be 60% more efficient than a stand alone heat strip model. If you have a large number of PTACs that are needed for heating as well as cooling, you may be able to save a substantial amount of money over the life of the unit.