Heat pumps that wring heat from outdoor air (and reverse the process in summer to act as an air conditioner) are inexpensive to install as an alternative to a cooling-only air-conditioning system. That makes them the preferred way to heat in the South and Southwest, where winters are typically short and mild. Heat pumps that wring heat from the ground are much more expensive to install, but they are suitable for cold climates because they can maintain their operating efficiency. Other inexpensive electric-heat options include strip heaters, which are installed in the ductwork of central air conditioning, and permanently installed baseboard units in each room. But before you consider any type of electric central heating in colder regions, keep in mind that electricity rates are much higher than those for natural gas and are likely to remain that way for the foreseeable future. You can get rate information for various fuels from local utilities and suppliers.
Partly to avoid that possibility, the furnaces in most homes are larger than necessary. Initial cost is only one of the drawbacks of that strategy. A furnace that's too large will cycle on and off more frequently. That puts more wear on its components, wastes energy, and might cause the temperature to vary uncomfortably. Also, a larger replacement furnace might require larger ducts. Without the right size ducts, airflow can be noisy.
You can make your home more energy-efficient in several ways. Turn down the thermostat in winter; just two degrees cooler will save you money and reduce emissions by about 6 percent. You might not even feel the difference, especially at night or when you're out of the house—a programmable thermostat can help here. Draw the curtains at night to block the chill from a cold window. Keep the windows covered on sunny days during the summer, and uncover them on sunny days during the winter to benefit from some free solar heating. Reduce heat loss from ducts by sealing leaks and, where feasible, insulating ducts.
High-efficiency condensing furnaces (90% AFUE and above) are a bit more complex than conventional furnaces. The main differences between a conventional and condensing furnace is the heat exchanger technology used to extract heat from the combustion process and the method used to exhaust the combustion gases. In these ways, the furnaces are very different. The condensing furnace does not have a significantly more efficient combustion process than does a conventional furnace; both use gas burners with electronic ignition. The difference lies in that the condensing furnace has a more efficient heat extraction process after combustion.