Furnaces & Boilers
Efficiency Standards History: The National Appliance Energy Conservation Act of 1987 (NAECA) established the initial minimum efficiency standards for furnaces and boilers, in terms of the annual fuel utilization efficiency (AFUE). Effective on January 1, 1992, it set the standards at a minimum value of 78 percent for most furnaces, 75 percent for gas steam boilers, 80 percent for other boilers, and 75 percent for mobile home furnaces. NAECA also required DOE to publish a standard for small furnaces (with input rates less than 45,000 Btus) and mobile home furnaces. In 1989, DOE published a final rule establishing an energy conservation standard of 78 percent AFUE for small gas furnaces (other than mobile home furnaces), with the effective date of January 1, 1992. DOE began a rulemaking for mobile home furnaces, but after the publication of the notice of proposed rulemaking (NOPR), a fiscal year 1996 moratorium on appliance energy conservation standards interrupted further activities on this rulemaking.
In September of 1993, DOE issued an advance notice of proposed rulemaking (ANOPR) that initiated a further standards rulemaking for furnaces and boilers. In its fiscal year 1998 Priority Setting for the Appliance Rulemaking Process, DOE assigned a low priority level to residential furnaces and boilers, which limited its work on these products. However, in the fiscal year 2001 Priority Setting, DOE identified residential furnaces and boilers as priority products for an updated standards rulemaking.
In 2000, the DOE initiated the process of updating the standards for residential furnaces and boilers. In July of 2001, it held a Framework Workshop to discuss the process for analyzing new standards. In 2002, DOE met with stakeholders to discuss the manufacturing analysis and published a draft version of the engineering analytical tools on the DOE web site. In May, 2003, DOE organized a public meeting to receive and discuss comments on issues related to venting installations for residential furnaces and boilers and to discuss DOE’s research concerning venting systems.
In July, 2004, DOE published an ANOPR in the Federal Register. The materials published for the ANOPR, including the technical support document (TSD), are available on DOE's Residential Furnaces and Boilers ANOPR webpage.
Product Description and Usage: Furnaces and boilers are common household space-heating appliances in the United States. NAECA defines residential furnaces as furnaces having a heat input rate of less than 225,000 Btus per hour (66,000 watts). It defines residential boilers as boilers having a heat input rate of less than 300,000 Btu/h (88,000 watts). On a national basis, 70 percent of households have residential furnaces and 11 percent have residential boilers. Over all, space-heating equipment accounts for over 70 percent of total gas consumption and 90 percent of oil consumption in the U.S. residential sector.
Technology: The residential furnace is an appliance that provides heated air through ductwork to the space being heated. It is equipped with a blower to circulate air through the duct distribution system. A typical residential furnace has the following basic components: cabinet or casing, heat exchanger(s), combustion system including burners and controls, forced draft blower or draft hood, and air filter and other accessories.
The residential boiler is a cast-iron, steel, aluminum, or copper pressure vessel heat exchanger designed to burn fossil fuels and to transfer the released heat to a suitable medium such as water (in water boilers) or water and steam (in steam boilers).
Efficiency Rating: Residential furnaces and boilers are rated by using the annual fuel utilization efficiency (AFUE) as an efficiency descriptor. AFUE represents the equipment's performance over an entire year’s heating season. It is intended to represent the effective annual operating efficiency of a furnace or boiler under dynamic conditions. It includes performance during start-up, steady-state, and cool-down operations. The AFUE is calculated from performance parameters that are measured under laboratory conditions using the DOE test procedure. These include a set of temperatures, the energy consumption, and a few other performance parameters. AFUE does not account for the electricity consumption of the appliance and therefore does not include the circulating air and combustion fan power consumption.
Product Classes: DOE divides residential furnaces and boilers into several product classes that may be subject to different efficiency standards. For the current update of the efficiency standards, DOE considered the following product classes:
- Weatherized and non-weatherized gas furnaces,
- Non-weatherized oil-fired furnaces,
- Mobile home gas furnaces, and
- Gas and oil-fired hot-water boilers.
Analyses: Under contract to DOE, LBNL's Energy Efficiency Standards (EES) group conducted analysis for the ANOPR, the NOPR, and the final rule for the Residential Furnaces and Boilers rulemaking, including:
- Rebuttable Payback Calculations
- Energy Consumption
- Life-Cycle Cost and Payback Period Analyses
- Shipments Analysis
- National Impact Analysis (National Energy Savings and Net Present Value)
- LCC Consumer Sub-group Analysis
- Utility Impact Analysis
- Employment Impact Analysis
- Environmental Assessment Report
- Regulatory Impact Analysis