what does emh mean on a thermostat
On a thermostat, “EMH” (often shown as “EM HEAT” or “Em Heat”) almost always refers to Emergency Heat , not a normal comfort mode.
Quick Scoop: What does EMH mean?
In plain terms, EMH = Emergency Heat , a backup heating mode used on systems with a heat pump.
When EMH is on, the thermostat tells your system to skip the outdoor heat pump and use the backup heat source only (electric strips, gas or oil furnace, etc.).
- It is meant for:
- Very cold weather when the heat pump can’t keep up.
* A problem or failure with the heat pump (frozen, broken, not running).
- It is usually:
- Hotter, but much more expensive to run than normal heat.
A simple way to picture it: EMH is like using your spare tire—great in an emergency, but not what you want to drive on every day.
When should you use EMH?
Use EMH only in special situations on a heat‑pump system.
You typically turn on EMH if:
- The outdoor unit (heat pump) is iced over, damaged, or obviously not running.
- Your thermostat or system shows a heat‑pump error and the house is getting cold.
- An HVAC tech or your system manual specifically tells you to run Emergency Heat.
You should not leave EMH on all winter just to “get more heat,” because:
- It bypasses the efficient heat pump and uses high‑cost backup heat.
- Running it for days can lead to very high electric or fuel bills.
Quick tips if you see EMH
- If you turned it on by accident, switch back to normal Heat mode and let the heat pump run.
- If EMH came on automatically and the outdoor unit looks frozen or dead, leave EMH on to stay warm, then call an HVAC technician.
- Check your thermostat’s manual: some brands also market “EMH” as an energy‑management / smart heat feature, but in most home heat‑pump setups it still links to Emergency Heat behavior.
TL;DR:
“EMH” on a thermostat almost always means Emergency Heat —a backup,
higher‑cost heating mode used when your heat pump can’t operate normally.