Currently, 14% of U.S. single-family homes use electric resistance heat to heat their homes: almost 11% have an electric central forced- air furnace, and more than 3% use some form of electric space heating. An additional 10% use heat pumps, which will be described in the next section.
Electric Central Furnaces
Electric forced-air furnaces distribute heat with an air handler and ducts, just like gas furnaces. The AFUE rating for an all-electric furnace is 95% to 100%. This is because electric furnaces provide heat through resistance, not combustion, so there are no heat losses up the chimney. All of the electricity is converted to heat, minus a small amount of heat loss through the air handler cabinet. This AFUE rating does not include any heat losses through leaky or uninsulated ducts. However, although it varies based on local utility rates, electricity is still one of the most expensive heating fuels.
If you have an electric furnace and your duct system is good, consider switching to a high-performance air-source heat pump. Electricity savings can be 30% or more when compared with electric resistance heating.
Room heating here refers to heating systems that heat one room or area of a home, unlike central systems, which distribute heat throughout the entire house via ducts or piping. Electricity is the most common fuel type for room heaters, but there are other fuel types as well.
Unvented combustion space heaters, which can release dangerous combustion gases into the home, are illegal in some states and should not be used. The use of portable space heaters is also not recommended because of their inefficiency and potential burn and tripping hazards.
In an average- or large-sized home with minimal or average insulation, electric resistance room heaters (baseboard or wall- mounted) are not typically a cost-effective method for heating the whole house over the long term. In a very well-insulated and air sealed home that requires little heating, they can be a cost- effective choice. They can also be a cost-effective choice for heating infrequently used rooms when the main living areas are heated with ductless heat pumps or radiant floor heat.
Many homeowners who have forced-air systems will shut vents and close a door in a room they aren’t using, thinking that this saves energy. This is not recommended because it can reduce airflow through the air handler, causing pressure imbalances, putting stress on the duct connections, and affecting air quality if you are using your air handler for ventilation. Zoning can be accomplished with central forced-air systems, using damper controls installed in the ducts by an HVAC professional, but the dampers will affect system efficiency and balance. In large homes, zoning of central heating and forced-air systems is more commonly (and more effectively) accomplished by installing multiple systems, with one unit per floor.
Hydronic heating systems can be configured, with piping and valves, to provide zone heating. Zone control works best in homes where the different zones can be isolated from each other with closable doors. Never shut off the heat entirely in an unused part of your home because condensation could form on cold inside wall surfaces leading to mold. Keep all rooms at a minimum of 50°F in the winter to prevent water pipes from freezing.
Room heaters can be used as an inexpensive way to provide zone heating when a central forced-air system is the main heating system for the home. Other forms of room heating that might be considered for supplemental heating or for additions include ductless heat pumps, electric radiant wall and ceiling panels, active solar space heating, sealed- combustion gas room heaters, and high-efficiency wood or pellet stoves.