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?

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.

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.

How Does It Know When to Kick In?

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 Dracut 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 New Era Plumbing & HVAC today!

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I am proud of the skills and knowledge I have gained during my 15 years working Plumbing and HVAC. I started as an apprentice, assigned to do basic tasks like carrying tools and materials, drilling holes and digging trenches. I was hungry to learn and expand my career opportunities, so I enrolled in an after-school training program for both my HVAC training and Journeyman license. I loved learning about both trades and felt like I was finally on the right track. When I passed my Journeyman Plumbing exam, I started to do side jobs which allowed me to experience the business owner side of things. This completely changed my perspective on my career and drove me to continue to pursue owning my own Plumbing & HVAC business. I continued my training and earned my Master’s license. With the support of my amazing wife, I started my own business SDP Plumbing, Heating and Cooling in 2016. Three years later, we rebranded the company as New Era Plumbing & HVAC. I could not be more proud of my career path and my company. Our core values are: Faith, Family, Empathy, Giving, Service and Quality. I train our team on adhering to these every day. We love taking care of our customers and are proud to serve our community.

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