Home Heating Systems: The Basics


home furnaceNatural gas furnaces are the most common heating source for U.S. homeowners. They’re used in more than 55 percent of American homes. Although most home furnaces are gas, they can also be fueled by propane and heating oil or run by electricity. Furnaces heat air, then use a blower motor to distribute warm air into your home through a series of vents and air ducts. Furnaces have a general life expectancy of 15 to 20 years.


Boilers heat water instead of air. They can be fueled by natural gas, propane, heating oil or electricity. Boilers heat water to very high temperatures that create either boiling water or steam, then it’s pumped into your home through a series of pipes. Boilers are relatively expensive to install and have a general life expectancy of 15 to 30 years.

Heat Pumps

Heat pumps create heat from outside air. They are typically fueled by electricity or geothermal energy. Air source heat pumps transfer heat from outside air, while geothermal heat pumps transfer heat from the ground. Both types distribute heat to your home through a series of air ducts, and in moderate climates heat pumps can also be used for air conditioning. Heat pumps have a general life expectancy of about 15 years.

How to Measure Your Home’s Heating Efficiency

Furnaces and Boilers

Heating efficiency of furnaces and boilers is measured by AFUE, Annual Fuel Utilization Efficiency, which measures how efficiently the furnace or boiler converts its fuel into heat. For example, an AFUE of 90 indicates that 90 percent of the fuel used is converted into heat. With furnaces and boilers, the higher the AFUE, the more efficient the unit. According to law, the Department of Energy requires all new furnaces and boilers to have a minimum AFUE of 78 to meet regulations. Old furnaces and boilers can have AFUE ratings as low as 60, while new Energy Star qualified units have AFUE ratings from 90 to 98. When purchasing a new furnace or boiler, it’s important to look for high AFUE ratings that indicate energy-efficient features.

Heat Pumps

Heating efficiency of air source heat pumps is measured by HSPF, Heating Seasonal Performance Factor, which calculates the energy used for heat, including defrosting and back-up heat. HSPF ratings for air source heat pumps range from 6.8 to 10.

As a professional, it’s important to educate your customers on the basics of home heating systems, including proper service and maintenance requirements according to the HVAC flat rate book.

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