Answer first, context after
What is the emergency heat setting on my thermostat?
Emergency heat tells a heat pump system to stop using the efficient heat pump and rely entirely on its electric backup elements, which produce heat at roughly triple the cost. It exists for the day the heat pump itself breaks. In Bakersfield's mild winters there is almost no other reason to touch it, and leaving it on by accident is a famous bill inflator.
That mysterious EM HEAT setting is the most misunderstood button on a heat pump thermostat, and misunderstanding it is expensive, so here is the whole story in plain terms.
What it actually does: a heat pump system usually includes electric resistance elements as a backup, like a big toaster inside the air handler. In normal operation the system runs the heat pump, which moves heat from outside air at a fraction of the cost of making it, and taps the elements briefly only when needed. Switching the thermostat to emergency heat locks the heat pump out entirely and runs the toaster alone. You get heat, delivered at the least efficient price the system is capable of.
What it is for: exactly what the name says. The heat pump itself has failed, a compressor issue, a refrigerant leak, a seized fan, and you need the house warm while you wait for the repair. Emergency heat is the spare tire: it gets you through, and you do not commute on it.
What it is not for: cold mornings. A common myth says the heat pump “can’t keep up” below some temperature and needs the switch flipped. Modern systems manage their own backup automatically, blending in the elements when genuinely required, and a Bakersfield winter, where hard freezes are rare and afternoons recover into the 50s and 60s, is gentle territory a heat pump handles without help. The system will make the right call faster than the switch will.
The expensive accident: emergency heat gets flipped on during a cold snap, or by a curious houseguest, and stays on for weeks. The house feels normal, because the heat is real, and the only symptom is an electric bill that arrives looking like a car payment. If your winter bill spiked mysteriously, checking this one switch is the fastest diagnostic in this entire library.
One legitimate exception: if the outdoor unit is visibly damaged or making grinding noises, flipping emergency heat on is the right move, because it keeps you warm while protecting the compressor from running itself to death. Then call, $89 to diagnose, waived with the repair, and we will get you off the spare tire quickly.
Still stuck? That's what the truck is for.
The diagnostic is $89, waived when you book the repair, with a written flat price before any work starts.