Improving the Performance of Wall Furnaces in California

Wall furnaces are prevalent in California’s single-family homes and low-rise multifamily residential buildings as primary or auxiliary sources of heating, but many have low thermal efficiencies. A recently completed study for the California Energy Commission and Southern California Gas Company shows high potential for cost-effective energy savings by replacing older existing wall furnaces with more efficient advanced retrofit models that can reduce emissions and improve indoor air quality.

GTI Energy researchers gathered information about furnace performance, operation, emissions, and indoor air quality from laboratory testing and field monitoring of baseline and retrofit wall furnaces. The oldest existing furnaces have thermal efficiencies of 50% while today’s standard replacement wall furnaces have thermal efficiencies of 70%.

By comparison, more advanced wall furnaces can achieve thermal efficiencies of 80-94%, delivering notable savings to consumers. These greater thermal efficiencies are achieved by eliminating pilot lights, using more efficient heat exchangers, and incorporating condensing or modulating technology. The retrofit packages developed by GTI Energy demonstrated payback on incremental costs within the life of the technology.