The vast majority of the energy consumed in American homes—90 percent, in fact—is used to power household appliances, such as heating and air conditioning systems. Air conditioners consume the most electricity of any appliance, accounting for 16 percent of residential electricity use. The production and consumption of energy for electricity increases CO2 concentrations in the atmosphere, contributing to the greenhouse effect, global warming, and climate change. On average, an air conditioner emits 2,263 pounds of CO2 every year.
Not only do air conditioners require large amounts of energy to function, much of the energy used to power an air conditioner is wasted. Recent studies have shown that 10 to 30 percent of cooled air in an average central air conditioning system escapes through ducts,. Lack of insulation also contributes to energy waste: the Rocky Mountain Institute (RMI) estimates that upgrading insulation in the attic, walls, and basement of a typical American home will reduce energy use and utility costs.
Air conditioners contain refrigerants, which, when released into the atmosphere, deplete stratospheric ozone, increasing human susceptibility to ultraviolet radiation and skin cancers. Chlorofluorocarbons (CFCs) were the main refrigerant used prior to 1987. In that year, the Montreal Protocol began a world-wide phase out of CFCs.
Hydrochloroflourocarbons (HCFCs) are substantially less damaging to the ozone layer, but still contain chlorine, a main element involved in ozone depletion. HCFC R-22 (a freon coolant) has been a popular refrigerant for the past few decades and is used in most air conditioning units today. Unfortunately, the manufacturing of HCFC R-22 contributes to global warming. R-22 is in the process of phase-out, and air conditioners are beginning to be manufactured containing ozone-friendly refrigerants, such as R-410A (known under different brand names, including Puron).
The choice between a central cooling system and a window unit (or single-room unit) should be based on a household's necessities and preferences. A window unit is less expensive to operate for cooling a single room, but is typically less efficient than central air conditioning for cooling an entire house. A central cooling system may be more appropriate if many rooms in the house are used often.
Both window units and central air conditioners have an efficiency rating that is regulated by the US Department of Energy. Single room units are rated by the Energy Efficiency Ratio (EER), while central air systems are rated with the Seasonal Energy Efficiency Ratio (SEER). Both ratios are measures of the cooling units produced (measured in Btus) divided by the energy consumption of the unit (measured in Watt-hours) over a single period of time. The higher the number, the more efficient the system. This rating must now be visibly attached to any new unit for sale.
Congress established a federal standard for EER in 1992, requiring that all single room air conditioners have an EER of at least 8.9.. In 2004, the Air Conditioning and Refrigeration Institute and the American Council for an Energy Efficient Economy agreed to manufacture all air conditioning equipment at an increased EER standard of 11.2 beginning January 2010.
As of January 23, 2006, all central air conditioners manufactured in or imported into the United States must achieve a SEER rating of 13 or higher (as opposed to the previous 1987 standard of 10). This regulation is expected to save US consumers 4.2 quadrillion Btus over the next 25 years, equivalent to the amount of energy annually consumed by 26 million American households. That represents a savings of over $1 billion. Air conditioning units that have been manufactured before this date can still be sold, and current air conditioner owners are not required to replace systems with a lower SEER rating. However, replacing an older system with a newer, more efficient one will be environmentally and economically advantageous in the long run.
In January 2001, the Clinton administration finalized legislation to increase the 1987 energy efficiency standard by 30 percent, increasing the minimum energy standard from SEER 10 to SEER 13. All new equipment sold in the US starting in January 2006 must comply with this ruling. However, in 2002, the Bush administration first delayed the new standard, and later weakened it, changing new minimum standards to SEER 12 (only a 20 percent increase from the previous standard).
The National Resources Defense Council (NRDC), 10 state attorneys general, and a coalition of consumer groups sued the Bush administration on the grounds that this rollback would increase US energy consumption, utility bills, and pollution production from power plants. The SEER 13 standard was projected to reduce the need for construction of 39 400-megawatt power plants, cutting nitrous oxide emissions by up to 85,000 metric tons and reducing greenhouse gas emissions by up to 33 million metric tons. By contrast, the SEER 12 was expected to prevent the need for construction of only 27 equivalent power plants, and would eliminate 14 percent of nitrous oxide and 27 percent of greenhouse gas emissions. In January 2004, a federal appeals court reinstated the Clinton administration's more efficient standard.
- Btu (British thermal unit): A unit of energy used universally in the heating and cooling industries. It is defined as the unit of heat required to raise 1 pound of water by 1 degree Fahrenheit.
- chloroflourocarbon (CFC): A haloalkane compound containing chlorine, primarily used as a refrigerant. When this gaseous compound reaches the stratosphere, UV light liberates the chlorine from the molecule and it is then capable of breaking down up to 100,000 ozone molecules (O3) into O + O2. Freon is a trademarked term referring to CFCs used in refrigeration and cooling systems.
- hydrochlorofluorocarbon (HCFC): A similar haloalkane compound where not all the hydrogen atoms are replaced by a halogen atom. These are typically used to substitute for CFCs, as the ozone-depleting capacity of these compounds is 10 percent less than that of CFCs.
- Puron: A brand name trademarked by Carrier that refers to the refrigerant 410A, a haloalkane that contains no chlorine and therefore does not contribute to ozone depletion.
- nitrogen oxides: Gases that contain nitrogen and oxygen produced during fuel combustion, such as in motor vehicles and electric utilities. When these compounds are released and exposed to sunlight and other gaseous compounds in the atmosphere, they can react to form smog, acid rain, and particulate matter that reduces breathing quality of air.
- Solar Energy International - Energy Facts
- Energy Information Administration - End-Use Consumption of Electricity 2001
- City of Stockton - Energy Efficiency: Residential Air Conditioning
- Rocky Mountain Institute - Energy Efficiency
- US Environmental Protection Agency - What You Should Know about Refrigerants
- Missouri Department of Natural Resources - Residential Energy Efficiency
- Environmental and Energy Study Institute - Air Conditioner Efficiency Standards
- Energy Information Administration - Glossary
- American National Standards Institute - Setting the Standards for Cool Times and Energy Savings
- US Department of Energy - Stronger Manufacturers’ Energy Efficiency Standards for Residential Air Conditioners Go Into Effect Today
- Do It Yourself.com - Understanding Energy Efficiency Ratings
- National Resources Defense Council - The Benefits of Reinstating the Clinton Air Conditioner Standard
- Environmental Protection Agency - Ozone Depleting Substances
- Carrier - Puron Refrigerant
- Environmental Protection Agency - Health and Environmental Impacts of NOx