Home Thermostats: What is Auxiliary Heat?

What is auxiliary heat on your thermostat? We’ve created this post to tell you exactly what it means and why you should care.

What is auxiliary heat anyway?  Should you be using it? What if it stays on all the time?

“Auxiliary” is not a word that we use much anymore so don’t feel bad if you’re a little confused.

Let’s explore what this is and why you need it.

Heat Pump Basics

To understand what auxiliary heat is we must first talk a little about your heat pump and electric resistance heat strip.

Within climates and times of year that have moderate heating and cooling needs, the heat pump is the most-energy efficient option. These pumps use electricity to transition heat from one place to another.

If you need to cool your house, the heat pump transfers warm air that’s inside to the outside to cool the house. In the winter, it reverses this function, bringing warmer air from the outside to moderate the temperature indoors.

The heat pump doesn’t generate any heat itself. Instead, it regulates heat between indoors and out. It slowly changes the indoor temperature to meet your preferences.

What is Auxiliary Heat?

Heat pumps are really a very fascinating, eco-friendly technology. But as you can imagine, the heat pump can only do so much.

If it’s 20 outside and you want to heat the house to 65, this would exceed what a heat pump can do.

When the demand exceeds capability during colder months, an electric resistance heat strip activates to help pick up the slack.

When Do You Need Auxiliary Heat?

When the temperature drops well below freezing, the heat pump can no longer pull enough heat from outside to warm the house. In these cases, the heat pump would switch over to auxiliary (or supplementary) heat as the electric resistance heat strip activates.

Additionally, sometimes moisture collects on the outdoor unit and freezes. In this case, the heat pump struggles to bring in warmer air. It needs help so the auxiliary heat comes on to lend a helping hand.

Auxiliary heat helps melt the ice and defrost the unit so that it can start working properly again.

Without auxiliary heat, the unit would attempt to defrost itself by reversing the flow of warm air out of the house to thaw the unit. Your home would, in turn, suddenly feel like a refrigerator.

But thanks to this function, this doesn’t happen.

What Is Auxiliary Heat Doing When It Stays on Auxiliary?

If your thermostat continues to indicate that you’re using auxiliary heat even when temperatures outside are above freezing, then your unit isn’t working in the energy-efficient way that it’s intended to work.

This can double or triple your heating bill.

Get it checked sooner rather than later as the bill will only rise. It could be a small fix and you’ll want to know.

Maintaining Your Auxiliary Heat

The auxiliary heat is an important function of your A/C system. It allows your unit to keep you comfortable in the most cost-effective way. It does this by only jumping in when the heat pump can’t handle things on its own.

If your auxiliary is staying on, you may need to get it checked out.

Be ready for the cold days ahead, Twin Cities! Save with our complete clean and inspection today.


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