Air Conditioners

By Kenton Shepard

Humidity Levels

Air conditioners help to dehumidify the incoming air, but in extremely humid climates or in cases where the air conditioner is oversized, it may not achieve a low humidity. Running a dehumidifier in your air conditioned home will increase your energy use, both for the dehumidifier itself and because the air conditioner will require more energy to cool your house. A preferable alternative is a dehumidifying heat pipe, which can be added as a retrofit to most existing systems.

Energy Consumption of Central Air Conditioners

Central air-conditioners are more efficient than room air conditioners. In addition, they are out of the way, quiet, and convenient to operate. To save energy and money, you should try to buy an energy-efficient air conditioner and reduce your central air-conditioner’s energy use.

In an average home, air-conditioning consumes more than 2000 kilowatt-hours of electricity per year, causing power plants to produce more than 3500 pounds of carbon.

Today’s best air conditioners use 30%–50% less energy to produce the same amount of cooling as air conditioners made in the mid 1970s. Even if your air conditioner is only 10 years old, cooling costs may be 20%–40% lower with a newer, more efficient model.

Energy Rating Of Air-Conditioners

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 13. Look for the ENERGY STAR label for central air conditioners with SEER ratings of 13 or greater.

New residential central air conditioner standards went into effect on January 23, 2006. Air conditioners manufactured after January 26, 2006 must achieve a Seasonal Energy Efficiency Ratio (SEER) of 13 or higher. SEER 13 is 30% more efficient than the previous minimum SEER of 10.

SEER ratings are not always listed on data plates. At times, determining the SEER rating will require research using the model or serial number.

You can compare air-conditioner efficiency using energy labels.

The standards do not require homeowners to change their existing central air conditioning units, and replacement parts and services should still be available for home systems. Manufacturers typically continue to support existing equipment by making replacement parts available and honoring maintenance contracts after new standards have gone into effect.

Retro-fitting Air-condition

Cold air is denser than warm air and requires larger ducts for distribution throughout the home. Air-conditioning systems added after the home was built often use the ducts originally installed for the heating system, often with unsatisfactory results. Results will be worse in homes with large, open stairwells.

Central Air-Conditioners

Central air-conditioners distribute cool air through a system of supply ducts which deliver cooled air to supply registers in the home. After circulating through the home, this cooled air becomes warmer and flows back to the central air conditioner through return registers and ducts to be re-cooled.

Split-System Air-Conditioners

In a split-system central air conditioner, an outdoor metal cabinet contains the condenser and compressor, and an indoor cabinet contains the evaporator. In many split-system air conditioners, this indoor cabinet also contains a furnace or the indoor part of a heat pump. The air conditioner's evaporator coil is installed in the cabinet or main supply duct of this furnace or heat pump. If your home already has a furnace but no air conditioner, a split-system is the most economical central air-conditioner to install.

Package System Air-Conditioners

In a packaged central air conditioner, the evaporator, condenser, and compressor are all located in one cabinet, which usually is placed on a roof or on a concrete slab next to the house's foundation. This type of air conditioner also is used in small commercial buildings. Air supply and return ducts come from indoors through the home's exterior wall or roof to connect with the packaged air conditioner, which is usually located outdoors. Packaged air conditioners often include electric heating coils or a natural gas furnace. This combination of air conditioner and central heater eliminates the need for a separate furnace indoors.