Household Heating Systems: Although several different types of fuels are available to heat our homes, nearly half of us use natural gas. | Source: Buildings Energy Data Book 2011, 2.1.1 Residential Primary Energy Consumption, by Year and Fuel Type (Quadrillion Btu and Percent of Total).
Heating and cooling your home uses more energy and costs more money than any other system in your home -- typically making up about 48% of your utility bill.
No matter what kind of heating and cooling system you have in your house, you can save money and increase your comfort by properly maintaining and upgrading your equipment. But remember, an energy-efficient furnace alone will not have as great an impact on your energy bills as using the whole-house approach. By combining proper equipment maintenance and upgrades with recommended insulation, air sealing, and thermostat settings, you can save about 30% on your energy bill while reducing environmental emissions.
U.S. Department of Energy - Energy Efficiency and Renewable Energy