what's the difference between heat and em heat
On a thermostat with a heat pump system, “Heat” and “EM Heat” (emergency heat) are two different modes that use different parts of your system and very different amounts of electricity.
Quick Scoop
- Heat : Normal, efficient heating mode that uses the heat pump (outdoor unit + indoor air handler).
- EM Heat (Emergency Heat) : Backup mode that shuts off the outdoor unit and heats your home only with the auxiliary/backup heater (electric strips or gas furnace), which is less efficient and more expensive to run.
- You use Heat for everyday comfort; you use EM Heat only when the heat pump can’t keep up or is malfunctioning.
What the “Heat” setting does
When your thermostat is on Heat with a heat pump:
- The outdoor unit runs and moves heat from outside air into your home, even when it feels cold outside.
- This process is highly efficient , so your energy bills are usually much lower than with electric resistance heat.
- If it gets very cold, many systems will automatically bring on auxiliary heat to help, without you touching EM Heat.
Think of Heat as the normal, budget-friendly mode for day‑to‑day winter use.
What “EM Heat” (Emergency Heat) actually means
EM Heat = Emergency Heat , not “extra heat.”
When you switch to EM Heat:
- The thermostat turns off the outdoor unit completely.
- Your home is heated only by the backup heater (electric heat strips or a gas/oil furnace).
- This mode is much less efficient , so your power usage and bills can jump noticeably.
You’re meant to use EM Heat only when:
- The outdoor unit is iced over, broken, or being serviced , and you still need heat.
- Temperatures are extreme and your installer or tech has specifically told you to use EM Heat temporarily.
Story-style example:
It’s a freezing night, and your heat pump’s outdoor unit suddenly stops working and starts making strange noises. You call a technician, and until they arrive, you flip the thermostat to EM Heat so the backup heater keeps the house warm, even though you know the electric bill will be higher.
Side‑by‑side: Heat vs EM Heat
| Feature | Heat | EM Heat (Emergency Heat) |
|---|---|---|
| What it uses | Heat pump (outdoor unit + indoor unit) | Backup heater only (electric strips or gas/gas furnace) |
| Efficiency | High efficiency, lower cost to run | Low efficiency, noticeably higher cost |
| Who turns it on | You set to Heat; system may auto‑add aux heat if needed | You manually choose EM Heat on the thermostat |
| Outdoor unit | Runs normally to move heat from outside to inside | Shut off/ignored while EM Heat is active |
| When to use | Everyday winter heating | Only when the heat pump is failing, iced, or under repair |
| Bill impact | “Normal” winter bills | Can cause a sudden spike in electric usage |
Common forum questions about EM Heat
“Should I turn on EM Heat when it’s just really cold?”
Usually no: most thermostats will automatically bring on auxiliary heat if the heat pump can’t keep up, without needing you to switch to EM Heat. Manually forcing EM Heat often just raises your bill without much benefit.
“Is EM Heat stronger or hotter than normal Heat?”
It can feel similar or slightly faster at warming because it’s direct resistance or furnace heat, but it’s not “super mode” — it’s expensive backup mode , not a comfort upgrade.
“I left EM Heat on for days, is that bad?”
It won’t harm the system in the short term, but it can be very bad for your wallet because you’re skipping the efficient heat pump entirely.
TL;DR
- Use Heat for normal operation — it’s efficient and uses the heat pump.
- Use EM Heat only in a true emergency when the outdoor unit can’t run or is being fixed, because it relies on costly backup heat.
Information gathered from public forums or data available on the internet and portrayed here.