Gas Furnaces

Furnace service.

Interstate Heating Co. is the leading HVAC company in Sussex, WI, for your furnace service needs. We service and repair all makes and models. If you need furnace service, we are the company to call. Our skilled technicians are qualified to solve just about any repair or installation that you throw at us.

How Much Money Can a New Furnace Save You?

Our AFUE energy savings calculator can help determine how much you could save on your utility bills. Simply enter your current unit's AFUE value and compare it to a newer, more efficient system. You can even customize it to better match your home's system for a more accurate calculation.

AFUE Energy Savings Calculator

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This calculator does not guarantee actual costs or savings and is only to be used for educational purposes.

Customize to Your Home

Adjust these settings for a more accurate calculation:




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Historical Comparison

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** Data from U.S. Energy Information Administration
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Furnace Repair

Don’t get left in the cold! Is your furnace acting up, blowing cold air, or making too much noise? Our experienced team of professionals is here to keep your home warm and cozy. We repair all makes and models, and we will never try to sell you a service that you don’t need. Our technicians are honest and hard working, and we’re always transparent and fair about the work we do.

Furnace Replacement

Sometimes a repair is not sufficient to fix your furnace. Sometimes a new furnace is the most cost-effective and energy-efficient way to go. We will always be honest with you about a possible furnace replacement. We value our time and your money––we don’t want to perform repairs or service on an appliance that is in need of replacement.

If you do need a furnace replacement, we know how overwhelming it can be. Here are some of the frequently asked questions about furnaces that we get from some of our Sussex, WI residents:

What Are The Different Types Of Furnaces?

Single Stage: A single-stage furnace has only one stage of operation. It can either be turned on or turned off.

Two Stage: A two-stage furnace has two settings––full and half speed. This is a more efficient way to heat and provides for better comfort, because it can move the air at a slower pace.

Variable Stage or Modulating: A variable-stage or modulating furnace modulates the speed and heat output based on the temperature outside and the desired comfort level. This furnace only works as much as you need it, making this type the most energy-efficient type of furnace.

What Is AFUE?

AFUE, or Annualized Fuel Utilization Efficiency, is a measure of furnace-heating efficiency. The higher the AFUE, the more efficient the furnace.

What Size Furnace Do I Need?

We can calculate the correct size furnace for your home. The number of BTUs, or British Thermal Units, needed to heat your home is dependent on a number of variables. Contrary to what you might think, a bigger furnace may not necessarily mean more heating power for your home. Call us at Interstate Heating Co., and we can set up an appointment to calculate the furnace size you might need.

Gas Furnace Maintenance in New Berlin, 53146

“Nice friendly tech did a good job and explained what he did.”
- Shane F.

Gas Furnace Maintenance in Waukesha, 53189-9215

“Eric was here for our usual fall Gas Furnace Maintenance inspection and answered many of our questions regarding our filters and the air quality in our home. Since we keep the furnace fan on continuously, there were questions about the Aprilaire control board. Some hints as to what number setting to use during the change of seasons in Wisconsin. He also offered information about our Air Quality and what we could do to take care of this situation. He was very professional, and we were very pleased with the exceptional service he provided.”
- Patricia S.

Gas Furnace Replacement in Pewaukee, 53095

“The crew from Interstate was top notch. From the moment they arrived (on time) and introduced themselves, to the moment they left, we were completely pleased with the work they completed. They left the work site as they found it, so there was no extra cleaning up needed after they left. I would highly recommend this company and the team that worked on our replacement furnace.”
- Cindy A.

Gas Furnace Maintenance in Pewaukee, 53072

“Kevin is great. Everything is in good shape. Ready for a Wisconsin winter.”
- Ron T.

Gas Furnace Maintenance in Pewaukee, 53072

“Nice polite young technician. Great to see in the trades.”
- Ted J.

Gas Furnace Repair in Sussex, 53089

“Efficient and professional”
- John E.

Gas Furnace Maintenance in Waukesha, 53189

“On time, professional, courteous & clean”
- Lana K.

Gas Furnace Repair in Sussex, 53089

“Got the part next day. Installed it same day a.m. Good quality and service.”
- David K.

Gas Furnace Repair in Waukesha, 53186

“Knowledgeable & fast. Very satisfied.”
- David H.

Gas Furnace Maintenance in Sussex, 53089

“Service technician was prompt, cordial, and friendly. Chris answered some questions of concern and explained several options.
Great service.
- David K.

Need Furnace Service?

Contact the experts at Interstate Heating Co.

Call us at 262-246-4772!