Notes on Buying a New Furnace


Now that winter is just around the corner, it’s more important than ever that your furnace is in working order. If you have been considering buying a new one, it’s essential that you learn the basics involved in the operation and installation of a furnace.

Service Legends has been servicing and installing furnaces for almost 20 years for our Des Moines neighbors. We can help you with all of your decisions regarding a new heating system, but it’s important to know the basics before beginning the conversation.

Look over these notes compiled by tech professionals and be ready to ask questions when you’ve made the decision to buy.


Central air systems come in two different designs; either a split system or a packaged system.  A split system is the more common of two, which consists of a condensing unit that sits outside and a furnace (and coil) placed inside the home. A packaged system contains the heating and cooling component in one unit that is installed outside. They are used in smaller homes or apartments without the extra space needed for the inside component of a split system.

Furnace Efficiency

A good rule of thumb is to always buy the most efficient furnace that you can afford. But this is made easier when you consider modern units have to meet minimum efficiency standards to comply with safety regulations. Efficiency is measured by AFUE (Annual Fuel Utilization Efficiency), which tabulates how much energy used by the furnace is converted into heating a residence. A furnace must reach a minimum of 80 percent AFUE in order to comply. The highest-rated modulating gas furnace reaches 97 percent AFUE.

Fuel Source

There are several fuel options available for furnaces, but some are dictated by where your house is located and what is available.

  • Gas: The most common is a gas furnace, which runs off natural gas and is the most economical of the types available. Most cities and suburban areas have gas lines that are readily available for use.
  • Oil or Propane: Homes where gas lines aren’t available sometimes use an oil or propane furnace. These units are more expensive to operate and require more room for storage (of the fuel). Oil and propane are also not as eco-friendly as gas but are viable options – especially for older homes and homes in rural areas.
  • Electric: An electric furnace is another alternative to gas, but it also more expensive to run. Electric units create heat from electricity, which can make a huge impact on your utility bill. However, these units are usually cheaper than their counterparts, are safer to use and easily can be converted to solar.

Hybrid Heat Pump

A heat pump might be an option if you live in an area that experiences mild winters, but Des Moines isn’t one of them. However, a hybrid heat pump system uses both an electric heat pump for electricity-fueled heating and cooling and a traditional furnace to step in when the temperature drops below 40 degrees. Used together, they can save a considerable amount on your energy bills, though the upfront cost is a bit higher than an average furnace.

Read more about our thoughts on hybrid heating.

Blower Options

Three different furnace blowers exist on the market; the single-stage, two-stage and variable speed.

  1. Single-Stage: Also referred to as “fixed-speed,” this option is not very efficient. It runs quickly and doesn’t always provide a consistent temperature throughout the home. It has one stage of heat output – high, which disperses the highest amount of energy possible.
  2. Two-Stage: These units operate much more efficiently than the single-stage counterparts. The first stage runs the majority of the time, using only about 65 percent of the full capacity. When the first stage is not enough to heat a home, the second stage kicks in to provide more heat.
  3. Variable Speed: With these units, the fan motor can operate at different speeds to better control the amount of heat dispersed throughout a home. This ensures that the air is delivered at a more consistent temperature and that the unit operates quietly (compared to the noisy single-stage blower). The motor can still operate even when the heat function is not turned on, which helps to keep the air circulated throughout the home.


In order for your furnace to run efficiently, it is important it is the correct size for your home. A system that is either too big or too small won’t be able to perform adequately and could break down prematurely. Additionally, proper sizing isn’t just about the size of the unit, it’s a variety of factors that need to be addressed. In order to find the ideal unit, an HVAC contractor will conduct a load calculation. This takes into account the climate, square footage of the home, the insulation, number of windows and more. It provides a solid framework for tabulating the appropriate furnace size. The standard that is used by most contractors is to provide at least 25 to 30 Btu (British thermal unit) of heat per square feet.

Heating and Cooling Des Moines Since 1997

When you are ready to look into a new heating unit, Service Legends can help with every facet of the project. From choosing the proper unit to installation and service, we’ll make sure that the process runs smoothly and as economically as possible. Call us today at 515-657-6634 and we’ll set up an appointment!

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