heating and AC, plumbing & electric
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February 9, 2022

What Is Aux Heat or Emergency Heat On My Thermostat & What Does it Do?

One question we get asked from homeowners quite often is “Why is the Aux Heat on my thermostat turned on?”

Are you finding your home just doesn’t feel comfortable temperature-wise in the winter? Is your family constantly complaining about being too cold? If this sounds familiar, you might not be using your system effectively. If you’ve noticed the words “aux heat” on your digital or smart thermostat, this might help with your thermostat settings. This heat pump feature stands for auxiliary heat.

The reason your thermostat has aux heat is that it indicates when gas or electric power has been triggered to help your heat pump reach a warm enough temperature when the weather outside is extremely cold. Unlike emergency heat settings which are run if your heat pump breaks, aux heat only kicks in when your heat pump can’t reach targeted settings and then turns off once the temperature is comfortable. It keeps your entire system running more efficiently while compensating when the heat pump just can’t provide enough heat quickly.

So, what is aux heat on my thermostat and how do I use it?

CITY emergency heat

Why Your Thermostat Shows Aux Heat

As mentioned above, your aux heat indicator turns on when your heat pump can’t reach the ideal temperature setting. Aux heat offers some help for your heat pump. While it comes from the same source as emergency heat, it actually is designed to support your heat pump to become more efficient as opposed to taking over completely. So it doesn’t cost as much to run as your emergency heat. “Aux” is short for auxiliary heat. If a heat pump is having a difficult time coming up to a certain temperature quickly due to extremely cold outdoor temperatures, the “aux heat” indicator means that a secondary heat source (generally gas or electric) has been deployed.

What is Emer. Heat or Emergency Heat on a Thermostat?

The difference between emergency heat and auxiliary heat is that emergency heat has to be switched on manually and should only be used in temperatures of 30 degrees or below. However, auxiliary heat will kick on automatically to help heat your home more quickly if there is a sudden drop in temperature.

emergency heat thermostat

How Does the Aux Heat Work?

Basically, when your heat pump detects it can’t heat up to reach the ideal temperature, it automatically energizes the aux “heat strip”. The heat strip is located inside your secondary heating source and helps your system reach warmer temperatures quickly. It’s like a boost to your heat pump. However, since these heat strips use massive amounts of electricity, you don’t want them running all the time. So, next, consider SHOULD auxiliary heat come on? Once your vents finally get the kick they need to warm up, the heat strips should turn off. Likewise, once ice melts on your unit, auxiliary heat should cease. If it keeps running, call a heating repair company as quickly as possible to avoid an enormous electric bill.

When Does the Aux Heat Kick On?

The need for that boost of auxiliary heat is determined by your thermostat. Your thermostat monitors any drop in temperature inside your home, and typically when they drop below your set temperature by 1.5-2 degrees your thermostat knows it’s time for your auxiliary heat to kick in. You know your aux heat is on when the aux heat indicator is on. Once your home reaches the ideal temperature, it will turn off the aux heat.

How Do I Set My Thermostat to React in Cold Temperatures?

If you aren’t sure if everything is set and working to keep your home comfortable in cold temperatures, you aren’t alone. Many people are unaware they even have an aux indicator. However, the first thing to know is that air exchange and geothermal heat pumps don’t remain efficient when the temperatures outside see extreme drops. Heat pumps often can’t work as hard as they should to counteract that outdoor cold and often struggle to maintain ideal temperatures once they reach the temperature setting.

When this happens, you might be wasting money, because your aux heat keeps having to run. So, in order to keep your heat running efficiently, you should use these heat pump thermostat tips:

  • Tip #1: Set temperatures higher in two-degree increments: While dropping temperatures might make it tempting to turn on your emergency heat setting, never do this. As mentioned, your emergency heat is designed for use in emergencies when your heat pump breaks. Instead, rely on your aux heat to work with your secondary heat source and your home’s heat pump to reach the right temperature. When you set your thermostat two degrees higher, you automatically trigger the aux heat. You reach your target heat quickly, and then it turns off, so you don’t waste more energy.
  • Tip #2: Watch the indicator to make sure it doesn’t turn on for outdoor temperatures higher than 40 degrees: If you notice your aux heat indicator is on even when temperatures outside aren’t so cold, it isn’t working properly. This wastes energy and requires the attention of a professional heat pump expert.

While your aux heat provides added comfort for your home in the cold of winter, whenever you find your home is constantly too hot or too cold, there is something not working with your heating system. In this case, you really should reach out to your local heating and cooling experts to have them come in and find out if you need repairs, or even a system replacement.


Find Long-Term Solutions

This is where we come in. As your home comfort experts, we can ensure your home remains comfortable all year round. We can help reduce energy waste and keep everyone happy. Give us a call at Paschal Air, Plumbing & Electric today!