What the Heck Is Aux Heat Anyway?

A Simple Guide for Homeowners in Madison, Indiana

If you have a heat pump, you’ve probably seen a mysterious term pop up on your thermostat in the winter: “Aux Heat.”

And if you’re like most homeowners around Madison, Columbus, and Seymour, you’ve probably wondered:

“Is something wrong with my system?”

“Why did my energy bill spike?”

“What the heck is Aux Heat anyway?”

Good news — Aux Heat is totally normal. But how it works does matter, especially during Southern Indiana winters.

Here’s a clear, non-technical breakdown.

What Is Aux Heat?

Auxiliary Heat (Aux Heat) is a backup heating mode for homes that use heat pumps.

In simple terms: It’s your heat pump calling for reinforcements.

When the heat pump can’t pull enough warmth from the outside air (because it’s freezing outside), it automatically switches on electric heat strips inside your air handler to help warm the home faster.

Why Does Aux Heat Turn On?

In Southern Indiana, Aux Heat usually kicks on when:

1. It’s extremely cold outside

When temperatures drop into the 20s and below — common in Madison — the heat pump struggles to extract enough heat from outdoor air.

2. You’re raising your thermostat quickly

Go from 65° → 72° in one jump?

Your system may use Aux Heat to reach that higher temperature faster.

3. Frost cycle / defrost mode

When heat pumps defrost themselves, they briefly run in cooling mode — so Aux Heat activates to keep your home comfortable.

4. Your system is undersized or needs maintenance

If Aux Heat turns on too often, something may be off:

• undersized heat pump
• dirty air filter
• failing thermostat sensor
• refrigerant issue

But occasional Aux Heat? Totally normal.

Is Aux Heat Bad?

Not ncessairly — but it is more expensive.

Heat pumps are highly efficient. Aux Heat strips are not.

Electric heat strips use a lot of energy, so seeing Aux Heat during a cold week may mean a slightly higher electricity bill.

However, if you’re seeing Aux Heat:

• constantly,
• when it’s only mildly cold outside, or
• even when your home already feels warm…

…then it’s time to have your system checked.

How to Reduce Aux Heat Usage

Here are simple ways Madison homeowners can save money:

✔ Change filters regularly

Dirty filters restrict airflow and force Aux Heat to help.

✔ Avoid big temperature swings

Use small adjustments or a smart thermostat that stages heat.

✔ Schedule a winter tune-up

A technician can:

• test heat strip operation
• check refrigerant
• improve airflow
• ensure your heat pump isn’t working harder than it should

✔ Inspect ductwork

Air leaks make your system run longer and rely on Aux Heat.

✔ Keep outdoor unit clear

Remove leaves, snow, or debris for maximum efficiency.

When Aux Heat Could Be a Sign of Trouble

Call Jackson Air if:

• Aux Heat runs constantly even at mild temps
• You hear unusual noises from the air handler
• Your thermostat frequently jumps into emergency heat
• Your winter bill suddenly spikes
• Certain rooms stay cold even when Aux Heat is on

These can indicate issues with:

• your heat pump compressor
• thermostat calibration
• heat strip wiring
• refrigerant levels
• airflow restrictions

Aux Heat vs. Emergency Heat

They sound similar, but they’re very different.

Mode	What It Means	Should You Use It?
Aux Heat	Automatic backup heat	Yes — system controls it
Emergency Heat	Manually turns off heat pump and uses only electric heat strips	No, unless heat pump fails

Emergency Heat is expensive and should only be used if the heat pump is malfunctioning.

Keep Your Heat Pump Running Efficiently This Winter

Aux Heat is normal — but shouldn’t be your system’s “default mode.”

If you’re concerned about how often it’s running or want to optimize your efficiency before the cold sets in, Jackson Air is here to help.

We provide:

• Heat pump tune-ups
• Heating repairs
• Blower door testing (EPA-certified)
• Energy efficiency consultations

📞 Schedule service at JacksonAir.com

Serving Madison, Columbus, Seymour, and surrounding Southern Indiana communities.