Back-Up Heat refers to a secondary heating source, such as electric heat strips, that engages when the outdoor temperature is too low for the heat pump to keep up. While our Hyper-Heat models rarely need this, it is a common safety feature in standard Multi-Zone systems in very cold climates. Back-up heat ensures that your home remains safe even during extreme weather anomalies. You can find heating Components and heat strip kits in our parts section for specific air handler models. Using back-up heat is less efficient than the "Reversible Cycle," so it is designed to be used sparingly. Most Single-Zone ductless units do not require a separate heat strip due to their advanced inverter logic. However, for "New Construction" in the far north, it is an important consideration for your "Manual J" calculation. This feature provides an extra layer of "Reliability" when the mercury drops to record lows.