Two-thirds of all homes in the United States have air conditioners. Air-conditioning use in the United States has increased more than 20% since 1984. Air conditioners consume 5% of all the electricity produced in the United States at a cost to homeowners of over $11 billion. As a result, roughly 100 million tons of carbon dioxide (CO2) is released into the air each year or an average of about two tons for each home with an air conditioner.
Switching to high-efficiency air conditioners and implementing measures to reduce cooling loads in homes could reduce this energy use by 20% to 50%. The most efficient air conditioners on the market are up to 70% more efficient than the current average room air conditioner.
About Room Air Conditioner Efficiency
A room air conditioner's efficiency is measured by the energy efficiency ratio (EER). The EER is the ratio of the cooling capacity (in British thermal units [Btu] per hour) to the power input (in watts). The required cooling capacity depends on the size of the room being cooled. The higher the EER rating, the more efficient the air conditioner. The minimum EER required is between 8.0 and 9.0. Units with an EER of 10.0 or above are considered very efficient. Most of the electricity consumed by a room air conditioner is used to drive the compressor. Only about 10% of the electricity is used to power the fan.
Tips for Buying a New Room Air Conditioner
When shopping for an air conditioner, first determine which type of system best suits your needs- central air conditioning or room air conditioning. Central air conditioners are designed to cool an entire house, while room air conditioners are usually window- or wall-mounted units that only cool the immediate area.
Three types of room air conditioners are available: (1) window models that can be installed in most double-hung windows; (2) casement window models that are used in narrow, vertical windows, usually requiring the removal of a window panel for installation; and (3) built-in models that are encased in a sleeve installed in the wall.
Proper sizing is very important for efficient air conditioning. A bigger unit is not necessarily better because a unit that is too large will not cool an area uniformly. A small unit running for an extended period operates more efficiently and is more effective at dehumidifying than a large unit that cycles on and off too frequently.
When determining the appropriate size air conditioner for your home, consider the dimensions of the area to be cooled. Based on size alone, an air conditioner generally needs 20 Btu for each square foot of living space. Other important factors to consider when selecting an air conditioner are room height, local climate, shading, window size, etc.
Verify that your home's electrical system can meet the unit's power requirements. Room units operate on 115-volt or 230-volt circuits. The standard household receptacle is a connection for a 115-volt branch circuit. Large room units rated at 115 volts may require a dedicated circuit and room units rated at 230 volts may require a special circuit.
If you are mounting your air conditioner near the corner of a room, look for a unit with an airflow in the desired direction for your room layout.
Look for a unit whose filter slides out easily for regular cleaning.
Select a unit with logically arranged controls, a digital readout for the thermostat setting, and a built-in timer.
When considering several comparable units, select the unit with the higher EER.
If you need to mount the air conditioner at the narrow end of a long room, then look for a fan control known as "Power Thrust" or "Super Thrust" that sends the cooled air farther into the room.
Tips for Lowering Your Room Air Conditioner's Energy Usage
While fans cannot replace air conditioners, they can provide supplemental cooling, especially on mild summer days. Substituting fans for air conditioners can reduce energy use by 60%.
Consider installing a programmable thermostat if you do not have one. You can save as much as 10% on your cooling bill by simply turning your thermostat back 10% to 15% for 8 hours. You can do this easily using a programmable or a setback thermostat.
Set your thermostat as high as comfortably possible in the summer. The less difference between the indoor and outdoor temperatures, the lower your overall cooling bill will be.
Don't set your thermostat at a colder setting than normal when you turn on your air conditioner. It will not cool your home any faster and could result in excessive cooling and, therefore, unnecessary expense.
Room air conditioners must be installed on a flat, even surface so that the inside drainage system and other mechanisms operate efficiently.
Set the fan speed on high, except on very humid days. When humidity is high, set the fan speed on low for more comfort. The low speed on humid days will cool your home better and will remove more moisture from the air because of slower air movement through the cooling equipment.
Consider using an interior fan in conjunction with your window air conditioner to spread the cooled air more effectively through your home without greatly increasing electricity use.
Don't place lamps or televisions near your air-conditioning thermostat. The thermostat senses heat from these appliances, which can cause the air conditioner to run longer than necessary.
It is important to install the unit in a shaded spot on the home's north or east side because direct sunshine on the unit's outdoor heat exchanger decreases efficiency.
Plant trees and shrubs to shade air-conditioning units but do not block the air flow. A unit operating in the shade uses as much as 10% less electricity than the same one operating in the sun.
Room air conditioners should be covered or removed and stored in winter.
Check your unit's air filter once a month and clean or replace filters as necessary. Keeping the filter clean can lower your air conditioner's energy consumption by 5% to 15%.
Clogged drain channels prevent a unit from reducing humidity, and the resulting excess moisture may discolor walls or carpet. Channels usually can be cleared by passing a stiff wire through them.
Holes in the seal between the air conditioner and the window frame allow cool air to escape from your home. Moisture can damage this seal, so inspect the seal annually to ensure it makes contact with the unit's metal case.
Written by: U.S. Department of Energy
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