Cooling - Choosing Or Upgrading Your Central Air-Conditioner Central air-conditioners are more efficient than room air-conditioners. In addition, they are out of the way, quiet, and convenient to operate. But to save energy and money, you should try to minimize your use of air-conditioning and lower your central air-conditioner's energy use. In an average air-conditioned home, air-conditioning consumes more than 2000 kilowatt-hours of electricity per year, causing about 3500 pounds of carbon dioxide and 31 pounds of sulfur dioxide to be emitted at the power plant.
If you are considering adding central air-conditioning to your home, the deciding factor may be the need for ductwork. If your home has ductwork for a forced-air heating system, you may be able to use it for air distribution. Whether or not your existing ductwork will work for air-conditioning depends on its size and your relative heating and cooling loads. Check with a heating and cooling contractor in your area.
If you have an older central air-conditioner, consider replacing the outdoor compressor with a modern, high-efficiency unit. Consult a local heating and cooling contractor to ensure that the new compressor is properly matched to the indoor unit.
Proper sizing and installation are key elements in determining air-conditioner efficiency. Too large a unit will not adequately remove humidity. Too small a unit will not be able to attain a comfortable temperature on the hottest days. Improper unit location, lack of insulation, and improper duct installation can greatly diminish efficiency.
When buying an air-conditioner, look for a model with a high efficiency rating. Central air-conditioners are rated according to their seasonal energy efficiency ratio (SEER). SEER indicates the relative amount of energy needed to provide a specific cooling output. Many older systems have SEER ratings of 6 or less. The minimum SEER allowed today is 10 for a split system and 9.7 for a single-package system. Look for the ENERGY STAR(r) label for central air-conditioners with SEER ratings of 12 or greater.
Other features to look for include:
* A unit that operates quietly
* A fan-only switch, so you can use the unit for nighttime ventilation to substantially reduce air-conditioning costs
* A filter check light to remind you to check the filter after a predetermined number of operating hours, and
* An automatic-delay fan switch to turn off the fan a few minutes after the compressor turns off. How To Buy Energy Efficient Central Air-Conditioners Figure 30 table shows you how to select energy efficient central air-conditioners. | Figure 30: Efficiency Recommendation | | Product Type (a) | Recommended Level (b) | Best Available | | Split Systems | 11.0 or more EER
13.0 or more SEER (c) | 14.6 EER
16.5 SEER (c) | | Single Package | 10.5 or more EER
12.0 or more SEER (c) | 12.2 EER
16.0 SEER (c) |
(a) Split system and single package units with capacity under 65,000 Btuh are covered here. This analysis excludes window units and packaged terminal units.
(b) This efficiency recommendation meets ENERGY STAR(r) specification effective October 1, 2002.
(c) SEER (seasonal energy efficiency ratio) is the total cooling output (in Btu) provided by the unit during its normal annual usage period for cooling divided by the total energy input (in Wh) during the same period. Based on DOE test procedure. | Cost-Effectiveness Example | | Performance | Base Model (a) | Recommended Level | Best Available | | EER | 9.2 | 11.0 | 14.5 | | SEER | 10.0 | 13.0 | 16.5 | | Annual Energy Use | 3,600 kWh | 2,770 kWh | 2,000 kWh | | Annual Energy Cost | $216 | $166 | $131 | | Lifetime Energy Cost (b) | $2,350 | $1,800 | $1,420 | | Lifetime Energy Cost Savings | ----- | $550 | $930 |
(a) The efficiency (SEER) of the base model is just sufficient to meet current U.S. DOE national appliance standards. The SEER efficiency of the base model is just sufficient to meet current U.S. DOE national standard. The EER of 9.2 of the base model shown represents the most common model on the market. SEER and EER may apply to different models.
(b) Lifetime energy cost is the sum of the discounted value of annual energy costs based on average usage and an assumed air-conditioner life of 15 years. Future electricity price trends and a discount rate of 3.2% are based on Federal guidelines (effective from April 2002 to March 2003).
Cost-Effectiveness Assumptions: Annual energy use calculation is based on the standard DOE test procedure. Central air-conditioner model: cooling capacity of 36,000 Btu/hr. Usage assumption: 1,000 cooling load hours per year. Assumed electricity price: $0.06/kWh, the Federal average electricity price (including demand charges) in the U.S.
Environmental Tips: Refrigerants with ozone-destroying chlorofluorocarbons (CFCs) were used many years ago in central air-conditioners but most existing equipment today uses HCFC refrigerants, which have a much lower ozone-depleting effect. There are some central air-conditioner models now on the market that use refrigerants with no ozone-depleting effect; ask your supplier for information. In the future, central air-conditioners with ozone-safe refrigerants are expected to be more widely available.
When retiring a central air-conditioner that contains CFCs or HCFCs, the Clean Air Act requires that the refrigerant be recovered on-site by a certified technician. For compliance info, contact the EPA Stratospheric Ozone Information Hotline at (800) 296-1996. Lowering Your Central Air-Conditioner's Energy Use * Set your thermostat at 78 degrees F or higher. Each degree setting below 78 degrees F will increase your energy consumption by approximately 8%.
* Use bath and kitchen fans sparingly when the air-conditioner is operating.
* Inspect and clean both the indoor and outdoor coils. The indoor coil in your air-conditioner acts as a magnet for dust because it is constantly wetted during the cooling season. Dirt build-up on the indoor coil is the single most common cause of poor efficiency. The outdoor coil must also be checked periodically for dirt build-up and cleaned if necessary.
* Check the refrigerant charge. The circulating fluid in your air-conditioner is a special refrigerant gas that is put in when the system is installed. If the system is overcharged or undercharged with refrigerant, it will not work properly. You may need a service contractor to check the fluid and adjust it appropriately.
* Reduce the cooling load by using cost-effective conservation measures. For example, effectively shade east and west windows. When possible, delay heat-generating activities, such as dishwashing, until the evening on hot days.
* Over most of the cooling season, keep the house closed tight during the day. Don't let in unwanted heat and humidity. If practical, ventilate at night either naturally or with fans.
* Try not to use a dehumidifier at the same time your air-conditioner is operating. The dehumidifier will increase the cooling load and force the air-conditioner to work harder. |
