If you’ve noticed AUX heating on your Nest thermostat, it usually means your system is engaging a two-stage heating process. The first stage, your heat pump, is highly efficient. However, when outdoor temperatures drop significantly, the heat pump might struggle to maintain the desired indoor temperature. That’s where AUX heat comes in—providing a backup source, such as electric resistance heat or a gas furnace, to keep your home warm.
Here’s the tradeoff: AUX heating is less energy-efficient than the heat pump. You’ll often see it activate during colder nights or extreme winter conditions. If your home is all-electric, you might notice the house heating up faster when AUX is active, but it can increase energy usage.
