Most heat pumps in High Point have a thermostat setting labeled EM HEAT or Emergency Heat. It is one of the most misunderstood buttons in the house, and leaving it on by mistake can make a power bill jump.
What emergency heat actually does
A heat pump moves heat from outdoor air into your home. Its backup is electric resistance heat strips inside the air handler, the same idea as a toaster element. In normal operation the thermostat brings those strips on automatically for a few minutes when the heat pump needs help, such as during a defrost cycle or on a very cold morning. That automatic help is called auxiliary heat.
Emergency heat is different. It shuts the outdoor heat pump off completely and heats the house on the strips alone.
When you should use it
Use emergency heat when the outdoor unit is not working: it is iced solid and will not defrost, the fan is not spinning, it is tripping its breaker, or it has storm damage. Emergency heat keeps the house warm until the outdoor unit is repaired or replaced.
You do not need it just because it is cold outside. Piedmont Triad winters are mild enough that a correctly sized heat pump with auxiliary heat handles normal cold snaps.
Why it costs more
Resistance heat makes roughly one unit of heat for each unit of electricity. A working heat pump moves several units of heat per unit of electricity. Running on emergency heat for days can noticeably raise your bill, so treat it as a temporary fix.
If you keep needing emergency heat
Frequent reliance on emergency heat usually means the outdoor unit has a failing part, a refrigerant problem, or is near the end of its life. That is the point to weigh repair against replacement.
FAQ
Is it bad to run emergency heat all winter?
It will not damage the system, but it costs more to run than the heat pump. Get the outdoor unit fixed or replaced.
Why does my thermostat say AUX HEAT?
That is the automatic backup helping the heat pump. It is normal for short periods.
Does a gas furnace have emergency heat?
No. Dual-fuel systems use the gas furnace as the backup instead of heat strips.
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