What size air conditioner do I need?

Heating, Cooling & Air Quality

If you’d like an air conditioner that can be used year-round, consider purchasing an air conditioner that’s also a heater.

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The best air conditioners for your household

Like clothing, an air conditioner must be the proper fit for it to be of value. If you buy one that’s too small or too large, you won’t be happy — or comfortable.

This article runs through the essential information you need to know before purchasing an air conditioner. It explains how an air conditioner works, what it does to the air in your room, how to choose the right sized air conditioner for your home and what happens if you get the wrong size.

How does an air conditioner work?

What does an air conditioner do?

An air conditioner removes the heat from the air inside your home and vents it outside. The result is the air in your house becomes cooler (and drier).

How does an air conditioner remove heat from the air?

An air conditioner uses a particular substance called a refrigerant that under the right conditions can absorb heat the way a sponge absorbs water. To do this, however, the refrigerant first needs to be compressed. To understand why this must happen, it might help to imagine squeezing (compressing) the bulb of a bulb syringe. 

When you release it, the bulb expands and sucks up whatever is in front of the tip. In essence, when the refrigerant expands, it sucks the heat out of the air, instantly cooling it. Since heat is energy and energy can’t be destroyed, heat must be vented outside your house to keep the inside cool.

What else does an air conditioner do besides remove heat?

When the air inside an air conditioner crosses the coils that contain the refrigerant, the water in that air condenses, the way moisture condenses on a cold glass of water on a hot day. This side effect removes humidity from the air, making it drier. In many climates, this is highly desirable, but in some places, the dry air can lead to dry skin and dry nasal passages.

In some units, the water removed from the air evaporates. However, in most instances, an air conditioner either needs to drain or be drained to get rid of the accumulating water.

How to choose the right size air conditioner

Air conditioners are sized by something called British thermal units. Luckily, you don’t need to know what BTU are to pick the perfect air conditioner. All you need to do is measure the width of your room and multiply those two numbers. This gives you the square footage of the room. Check the chart below to find out the best size air conditioner for you.

For example, a room that’s 20 feet long by 10 feet wide is 200 square feet. If you check the Energy Star chart below, you discover you need a 6,000 BTU air conditioner. It’s that easy. 

  • 100-150 square feet needs 5,000 BTU
  • 150-250 square feet needs 6,000 BTU
  • 250-300 square feet needs 7,000 BTU
  • 300-350 square feet needs 8,000 BTU
  • 350-400 square feet needs 9,000 BTU
  • 400-450 square feet needs 10,000 BTU
  • 450-550 square feet needs 12,000 BTU
  • 550-700 square feet needs 14,000 BTU
  • 700-1,000 square feet needs 18,000 BTU

Since air conditioner manufacturers only make a few sizes of air conditioners, you might not find an exact match. If this is the case, go with the next larger size. For example, if you need a 7,000 BTU unit but only have the option of a 6,000 BTU or 8,000 BTU air conditioner, go with the larger model.

What happens if my air conditioner is too small?

If you buy an air conditioner that’s too small to cool the room, it will constantly run, cranking up your energy bill while not effectively cooling the space. It will also shorten the lifespan of your air conditioner.

What happens if my air conditioner is too large?

Many people think that going with the most significant model is the best, but this isn’t the case. The refrigerant must go through a cycle to be efficient. Purchasing an air conditioner that’s too big won’t allow the unit to finish the compression cycle. As a result, the air conditioner won’t be running long enough to be effective as a dehumidifier or adequately circulate the air, so you may still have hot spots and damp air. Additionally, the air conditioner constantly turning on and off can shorten the lifespan of the unit.

Which is better: a portable or window air conditioner?

The two main options you have for air conditioners are a portable model that sits on the floor or a semipermanent model installed in a window. Since both models must be vented outside through a window (yes, even the floor model), it’s a matter of user preference which design is best for you. If you like bells and whistles and portability, a floor model might be more desirable. However, a window unit saves floor space and doesn’t need to be emptied (it drains out the back of the unit), so some individuals might prefer that as an option.

Why does my portable air conditioner have two BTU ratings?

In 2017, the Department of Energy updated how it measured BTU. The newer system takes several additional cooling factors into account. This results in a lower BTU rating. It’s important to understand that the air conditioners aren’t less efficient; the rating system has just changed. For consistency and ease of comparison, all models in the following section are listed with the older standard of the American Society of Heating, Refrigerating and Air-Conditioning Engineers.

Best air conditioners

GE 6,000 BTU Electronic Window Air Conditioner

GE 6,000 BTU Electronic Window Air Conditioner

For small rooms, this GE window air conditioner is a solid model. It features three cooling levels and three fan speeds along with an energy-saver mode to help reduce energy bills.

Where to buy: Sold by Amazon

Frigidaire 8,000 BTU Portable Air Conditioner

Frigidaire 8,000 BTU Portable Air Conditioner

This portable floor unit has three fan speeds and remote control for convenience. This unit operates off a standard household outlet.

Where to buy: Sold by Amazon and Staples

BLACK+DECKER 14,000 BTU Portable Air Conditioner

BLACK+DECKER 14,000 BTU Portable Air Conditioner

This higher-end portable air conditioner features quiet running for sleeping, remote operation and a bucket-less, self-evaporating system. The 24-hour timer allows you to control the temperature day and night.

Where to buy: Sold by Amazon and Wayfair

LG Electronics 14,000 BTU Smart Window Air Conditioner

LG Electronics 14,000 BTU Smart Window Air Conditioner

This window air conditioner is best for the individual seeking all the bells and whistles. It’s Energy Star certified and can be controlled via a remote or by using the LG ThinQ app on your smartphone. It’s also easy to install, features a sleep mode and has an auto-restart if you ever lose power.

Where to buy: Sold by Home Depot

 

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Allen Foster writes for BestReviews. BestReviews has helped millions of consumers simplify their purchasing decisions, saving them time and money.

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