Lawrence Berkeley National Laboratory

This paper presents analysis of the life-cycle costs for individual households and the aggregate energy and economic impacts from potential energy efficiency improvements in U.S. residential furnaces. Most homes in the US are heated by a central furnace attached to ducts for distributing heated air and fueled by natural gas. Electricity consumption by a furnace blower is significant, comparable to the annual electricity consumption of a major appliance. Since the same blower unit is also used during the summer to circulate cooled air in centrally air conditioned homes, electricity savings occur year round. Estimates are provided of the potential electricity savings from more efficient fans and motors. Current regulations require new residential gas-fired furnaces (not including mobile home furnaces) to meet or exceed 78 percent annual fuel utilization efficiency (AFUE), but in fact nearly all furnaces sold are at 80 percent AFUE or higher. The possibilities for higher fuel efficiency fall into two groups: more efficient non-condensing furnaces (81 percent AFUE) and condensing furnaces (90-96 percent AFUE). There are also options to increase the efficiency of the furnace blower. This paper reports the projected national energy and economic impacts of requiring higher efficiency furnaces in the future. Energy savings vary with climate, with the result that condensing furnaces offer larger energy savings in colder climates. The range of impacts for a statistical sample of households and the percent of households with net savings in life cycle cost are shown. Gas furnaces are somewhat unusual in that the technology does not easily permit incremental change to the AFUE above 80 percent. Achieving significant energy savings requires use of condensing technology, which yields a large efficiency gain (to 90 percent or higher AFUE), but has a higher cost. With respect to electricity efficiency design options, the ECM has a negative effect on the average LCC. The current extra cost of this technology more than offsets the sizable electricity savings.