Old coal burners that were switched over to oil or gas are prime candidates for replacement, as well as natural gas furnaces with pilot lights rather than electronic ignitions. If your furnace or boiler is old, worn out, inefficient, or significantly oversized, the simplest solution is to replace it with a modern high-efficiency model. Upgrading your furnace or boiler from 56% to 90% efficiency in an average cold-climate house will save 1.5 tons of carbon dioxide emissions each year if you heat with natural gas, or 2.5 tons if you heat with oil. Energy efficiency upgrades and a new high-efficiency heating system can often cut your fuel bills and your furnace's pollution output in half. Other retrofitting options that can improve a system's energy efficiency include installing programmable thermostats, upgrading ductwork in forced-air systems, and adding zone control for hot-water systems, an option discussed in Heat Distribution Systems.Īlthough older fossil fuel furnace and boiler systems have efficiencies in the range of 56% to 70%, modern conventional heating systems can achieve efficiencies as high as 98.5%, converting nearly all the fuel to useful heat for your home. Gas-Fired Furnaces and Boilers (includes units fired with natural gas and propane).Retrofits are fuel-specific, so see the following sections for retrofit information: If you choose to replace your heating system, you'll have the opportunity to install equipment that incorporates the most energy-efficient heating technologies available. The costs of retrofits should be carefully weighed against the cost of a new boiler or furnace, especially if replacement is likely within a few years or if you wish to switch to a different system for other reasons, such as adding air conditioning. These upgrades improve the safety and efficiency of otherwise sound, older systems. Condensing flue gases in a second heat exchanger for extra efficiencyįurnaces and boilers can be retrofitted to increase their efficiency.Compact size and lighter weight to reduce cycling losses.Exhaust fan controls the flow of combustion air and combustion gases more precisely.Natural draft that creates a flow of combustion gases.You can identify and compare a system's efficiency not only by its AFUE but also by its equipment features. Read about the standards for residential furnaces. If you are interested in electric heating, consider installing a heat pump system. However, despite their high efficiency, the higher cost of electricity in most parts of the country makes all-electric furnaces or boilers an uneconomic choice. The lower values are for units installed outdoors because they have greater jacket heat loss. The AFUE rating for an all-electric furnace or boiler is between 95% and 100%. AFUE doesn't include the heat losses of the duct system or piping, which can be as much as 35% of the energy for output of the furnace when ducts are located in the attic, garage, or other partially conditioned or unconditioned space.Īn all-electric furnace or boiler has no flue loss through a chimney. An AFUE of 90% means that 90% of the energy in the fuel becomes heat for the home and the other 10% escapes up the chimney and elsewhere. Specifically, AFUE is the ratio of the furnace's or boiler's annual heat output compared to its total annual fossil fuel energy consumed. AFUE is a measure of how efficient the appliance is in converting the energy from fuel to heat over the course of a typical year. The Federal Trade Commission requires new furnaces or boilers to display their AFUE so consumers can compare heating efficiencies of various models. A central furnace or boiler's efficiency is measured by annual fuel utilization efficiency (AFUE).
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