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Should I Switch My Thermostat to “Emergency Heat” If It’s Super Cold Outside?

Posted 02-07-14 in Heating

Short answer: No. Switching your thermostat to emergency heat or “em heat” just because it’s cold outside will just raise your energy bills like crazy.

Don’t use emergency heat mode unless your heat pump stops heating your home altogether.  

If that happens, contact a professional heat pump repairman for help.

Why would emergency heat mode run up your energy bill? To understand, we need to briefly cover how a heat pump works

How a heat pump works and how it relates to em heat

Your heat pump can heat your home in 3 ways:

  • Moving heat- In heat mode, your heat pump is like an air conditioner working in reverse to pull heat from the outside to inside your home (the opposite of how it works in cooling mode).
  • Electric heat strip- This electric heat strip is auxiliary heating (or “aux heat” as it shows up on your thermostat). It comes on automatically to help heat your home when your heat pump struggles to pull in heat when it’s below 40 degrees F outside.
  • Backup gas furnace- Many homeowners use their gas furnace in place of the electric heat strip for auxiliary heat at lower temperatures.

It costs more to use the auxiliary heat, especially the electric heat strip since it runs off electricity. That’s why energy.gov says heat pumps are more efficient in milder temperature climates—they don’t need to use the heat strip or gas furnace as often.

“Emergency heat” means constantly using the backup heat

Switching your thermostat to emergency heat is you telling your heat pump this:

“Hey, stop trying to pull in air from outside. Just use your backup heat.” Your heat pump gladly complies. But now your heat pump basically works either as an electric furnace, which costs more to use than a heat pump, or it’s using the backup furnace.

The backup furnace works more efficiently than the heat strip, but less efficient than the heat pump pulling in heat.

Either way, you don’t want to switch over to emergency heat just because it’s cold outside. Your heat pump will use the auxiliary heat on its own to supplement heating your home.

When to use emergency heat

Only use it...in a heating emergency! Make sense, right?

Use emergency heat only if your heat pump isn’t heating your home at all. That’ll keep you warm until a professional heat pump contractor can come repair it.

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Coolray is your Atlanta-area home comfort expert with specialists in heating, air conditioning, air quality and plumbing. Have more questions? We’d be happy to help – just contact us online.

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