What EM HEAT actually does
A heat pump heats your house by pulling heat out of the outside air and moving it inside, even when it's cold out. It's an efficient way to heat. Most heat pump systems also have electric heat strips in the indoor unit, a backup that works a lot like the coils in a toaster.
When you switch the thermostat to emergency heat, you're telling the system to shut the outdoor heat pump off and heat the house with those electric strips alone. The house still gets warm, but it costs a lot more to run. Utilities like Jackson EMC estimate backup heat can cost about two to five times as much as normal heat pump heating.
Take a look at your thermostat today and find out if it has an EM HEAT or Emergency setting, and make sure it's not turned on. If it says "Emergency" on the screen and you didn't mean to set it, switch it back to regular Heat.
Source: Jackson EMC
Source: Google Nest Help
AUX heat vs. emergency heat
These two get mixed up all the time. AUX, or auxiliary heat, comes on by itself. On a really cold morning, during a defrost cycle, or when you bump the thermostat up several degrees at once, the system brings in the heat strips to help the heat pump catch up. Seeing AUX on the screen now and then is normal.
Emergency heat is different. You have to turn it on by hand, and it stays on until you turn it off. The heat pump sits idle the whole time, no matter how mild it gets outside.
To keep AUX heat from running more than it needs to, raise the thermostat a degree or two at a time instead of five or six at once. A steady setting is easier on a heat pump, and on your power bill.
Source: Trane Home Support
When you should use it
Emergency heat is for an actual emergency: the outdoor unit has stopped working. Maybe it's making a loud grinding or banging noise, it's iced over solid and won't defrost, a tree limb hit it, or the house just won't warm up and the outdoor fan isn't running. In that case, switching to EM HEAT keeps the house warm and keeps the pipes safe until the system gets looked at.
What it's not for is everyday cold weather. A working heat pump with AUX heat handles a Georgia winter fine.
If you have to use emergency heat, treat it as a bridge, not a fix. And if you notice AUX or EM HEAT running all the time, that's a sign something needs attention. Don't open the outdoor unit or touch the refrigerant lines yourself. Give me a call at (470) 999-7395 for a $79 diagnostic, and I'll find out why the heat pump isn't carrying the load.
