The Energy Efficiency Ratio of Room Air Conditioners

The higher the rating, the more efficient the unit

Woman adjusting thermostat
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Room air conditioners can be an affordable way to cool a limited space, rather than using a central cooling system to cool a whole home or office building, particularly if there is unused space. While less efficient than central air, they can be significantly cheaper to operate

Energy Efficiency

A room air conditioner's efficiency is rated according to the Energy Efficiency Ratio (EER). This is the ratio of cooling capacity to the power input, or how well it cools compared to how much energy it needs. The ratio is measured in British thermal units (Btu) per hour. The higher the EER, the more efficient the unit. If you're shopping for a new air conditioner, look up its EER. 

How to Select an Air Conditioner

The required cooling ability and strength of the air conditioner you need is based on the size of the room you plan to use it in. Getting a big, overly strong air conditioner can be a bad idea for a smaller room. It can cause the unit to work incorrectly, causing the room to feel damp or spotty. A smaller unit intended for that space works consistently and will dehumidify the room like it's supposed to.

Based solely on size, a good rule of thumb to follow is the unit will need 20 Btu for every square foot of space. But if you have a room with a vaulted ceiling or are located in an especially hot climate, you will need to go a bit higher to get a good air conditioner. Before purchasing, make sure your home or business has the ability to run the unit. Room units usually run on a 115-volt or 230-volt circuit.

Additionally, consider what extra features are important to you. Some units are programmable, cooling more at certain times of the day and letting the room get warmer at different times when no one is in the room. This automatic feature can help save you money. Also look for units with an easily removed filter, to make cleaning more simple and convenient. A digital readout can also help you set the unit to the precise temperature for efficiency, usually around 78 degrees Fahrenheit.

Operating the New Unit

Position the new air conditioner away from other appliances, such as lamps or the television. These devices can give off heat and trick the unit into working harder than it needs to, using up more energy.

Set the unit to a temperature that is as high as you can comfortably handle. Going below 78 degrees makes your unit have to work much harder, which can greatly increase your electricity bill.

By understanding what to look for when shopping for an air conditioner, you can make an informed choice that fits your needs and your budget. Consider the unit Energy Efficiency Ratio, voltage, and Btu to get the best air conditioner for you. By using an energy-efficient air conditioner strategically, you can stay comfortable while keeping your electric costs down.