As winter settles in, plummeting temperatures outside mean it's time for households across the country to start firing up their heaters and furnaces. Since winter heating costs are usually the single largest expense on the average family's energy bills, it's important to look for the most efficient appliances you can find so you don't break your budget in the name of staying warm. However, keep in mind that winter warming requirements vary greatly depending on what region of the country you live in -- the best furnace option for a family in frigid Fargo, N.D., is not going to look the same as that for someone living in a more mild area like Arizona or New Mexico.

For guidance, look to Energy Star, the federal program that certifies high-efficiency appliances, which breaks its furnace rankings into two:

If You Live in the South

Since people who rarely experience freezing temperatures require dramatically less energy overall to stay warm in the winter, they don't have to invest in the most advanced heating models to get the federal thumbs-up. The 21 states with the mildest winters include most of the south and southwest and creep up the coasts as high as northern California in the west and Delaware in the east. Qualifying heaters in these areas get stamped with a “U.S. South” Energy Star Logo. To meet the standard, gas heaters must have an annual fuel utilization efficiency, or AFUE, of at least 80. The southern-specific certification promises that the appliances are up to12 percent more efficient than standard models.

People living in warmer states have other options, such as heat pumps, which can save a bundle in energy costs but don't work well when temperatures dip below 41 degrees.

If You Live in the North

In the rest of the country, where households require more heating power in the winter, standards are stricter. Look for the standard Energy Star label for furnaces that are as much as 16 percent more efficient than average models and have AFUE ratings of 90 or higher.

There are also other heating-related home guidelines that can vary depending on where in the country you live.

Of course, no matter where you live, you can save money and help reduce fossil fuel consumption by taking other measures to shore up your efficiency, like fixing drafty windows and using a smart thermostat. An HVAC professional can run an energy audit on your house to find places where you can realize savings and make sure you're getting the most for your money.

Contact your local One Hour Air Conditioning and Heating® technician for advice on choosing and maintaining your heating system and for more tips on heating your home efficiently.