The lock-out temperature is a programmed setting that prevents a heat pump from running when the outdoor air is too cold to be efficient. At this point, the system will typically switch to a backup heat source, such as Heat-Strips or a gas furnace. This protects the compressor from unnecessary wear and ensures your home remains warm during extreme freezes. You can often adjust these settings if you are using a multi-position air handler with a smart thermostat. Understanding your unit’s efficient operating range is vital for long-term ROI. We recommend checking the technical specs of our heat pump systems before deciding on a backup heat source.