What Size Air Conditioner

How much will an Energy Star air conditioner save me?

In our latest report on air conditioners , you'll notice that all of our Best Reviewed selections are Energy Star qualified (you can learn more about the Energy Star program for air conditioners here ). That's not a real shocker. After all, if you're replacing a broken window air conditioner, or buying one for a new location in your home, there's no question that an Energy Star qualified AC will cost less to operate -- about 10 percent less, experts say --  than one that is not. To be fair, however, your actual savings in dollars and cents can vary a bit, and will depend on things like how much you will use your new air conditioner and how much electricity costs where you live. What about replacing a still-working but older, non-energy efficient air conditioner? Can a new Energy Star air conditioner save enough electricity to at least pay for itself while reducing your carbon footprint? Let's find out.

Energy Star for air conditioners: What does it mean?

To even be sold in this country, a room air conditioner has to meet a federal standard for energy efficiency. To gain Energy Star status, a room air conditioner must exceed the federal standard by at least 10 percent, and the threshold to qualify for the Energy Star program is expected to go up in October 2012.

For energy standards to have any validity there needs to be some type of consistent measuring stick. For room air conditioners, that's their Energy Efficiency Ratio, or EER. The EER is found by dividing an air conditioner's cooling power (in BTU, or British Thermal Units, per hour) by the amount of electrical power (in watts) it requires to deliver that cooling at a specific outside temperature (95 degrees F).

An air conditioner's EER rating can be found on its yellow EnergyGuide label, and the higher the EER the better. For example, an air conditioner with an EER of 10.8 (what an average sized air conditioner of between 8,000 and 13,999 BTUs needs to gain Energy Star acceptance) will be more energy efficient than air conditioner of the same size with an EER of 9.8, which just meets the minimum federal energy standards.

Crunching the numbers

Now that we are armed with some information, it's time to see just how much you can save by going with an Energy Star qualified AC over one that just meets the minimum standards. For this example, let's consider our Best Reviewed 10,000 BTU air conditioner, the Frigidaire FRA106BU1 , which is Energy Star rated and has an EER of 10.8, with a non-Energy Star rated air conditioner that just meets the minimum federal standard of 9.8 EER. We'll also use the current national average for electrical rates, which is 11.2 cents per kilowatt hour -- though check your own electric bill as you could be paying less or more.

What Size Air Conditioner Will Fit My Home? | Pompeii's Plumbing ...

When you are trying to determine what size air conditioner to get, the first thing you need to know is how large the space you want to keep cool is. Air conditioners come in a wide variety of sizes and each is appropriate for a particular type of space. So once you know how big the space is, you will be able to compare that to the capacities of the various air conditioners out there to find the right one for your needs.

The cooling power of air conditioners is actually measured in British Thermal Units, or BTUs. Each BTU rating corresponds to a particular square footage which that air conditioner should be able to cool properly and efficiently. For instance, a 10,000 BTU air conditioner can cool a room that measures between 400 and 450 square feet, and so forth. The higher the BTU, the larger the area the air conditioner can acceptably cover.

It is pretty easy to see why you would not want to pick out an air conditioner that is too small for the space you need to cool. The system simply would not be able to keep the space cool enough and it would use a lot of energy trying.

However, that does not mean that the bigger the air conditioner is the better. In fact, you will do just as poorly to purchase an air conditioner that is too big for the space you want to cool than one that is too small. This is because air conditioners do more than cool the room. They also remove humidity as they cool the space.

An air conditioner that is too large will cool the room quickly, causing it to switch on and off frequently. Not only is this annoying because of the noise that the air conditioner makes, but it also increases the wear and tear that the unit must endure. An air conditioner that is too big will also not be able to remove humidity as efficiently because the room is cooled so quickly. Plus, it will use much more energy than necessary to do a sub-standard job.

With these types of calculations, it is relatively easy to pick out a single room air conditioner. However, if you are trying to purchase a whole home air conditioning system, you will probably need a professional to help you figure out exactly how powerful you need the system to be to keep your home comfortable and cool all summer long.

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