AC vs. Fans


As an Arlington resident, I am no stranger to the humming of air conditioners at night. My family owns an air conditioner, but we never use it unless there are guests. Why? Because, frankly, we don't need it. Fans work fine for us, and if it gets really bad we just get some ice and rub it on ourselves. Often, though, I hear the AC humming from our neighbors' houses on nights when I am perfectly comfortable. I wondered why people would use electricity like this, and decided to research how much this costs my neighbors. The following is the product of my research.



 Ignoring the cost of the conditioner itself, hundreds of dollars are spent a year on electricity for air conditioners. Fans are cheaper and use much less energy. By switching to fans, you can save money and still keep cool. Of course, this doesn't mean that you should never use air conditioners. I suggest using fans unless it is above 90 degrees. In that case, air conditioning is probably worth the extra cost. Just using the AC more sparingly can dramatically decrease your yearly electrical bills.

Assumptions

  • The data I gathered was from Arlington, Massachusetts.
  • I made certain assumptions about what the average household uses on days above 80 degrees:
    • 3 fans would be used 24 hours a day.
    • 2 window AC units would be used 12 hours a day.
    • 1 central air 2.5 ton unit would be used 12 hours a day.
  • In 2010, there were 75 days above 80 degrees.
  • In Massachusetts, a KwH costs 12.8 cents.

The Numbers

The total cost per year comes from the product of the five previous numbers.

 		KWH/H Hours of use on day above 80 degrees Number in Use Cost per KWH (Massachusetts) 2010 number of days above 80 Total Cost per year
Window AC Unit 0.9 14 2 12.8 75 $241.92
Central Air 2.5 ton 3.5 14 1 12.8 75 $470.40
Fans (all types) 0.075 14 3 12.8 75 $20.24

As you can see, hundreds can be saved by switching to fans, or just using window units in a couple of rooms instead of the whole house. You only need air conditioning in the room you are in. Central air cools the whole house, which is a total waste of electricity. Some people need air conditioning when it gets really hot. I suggest for those people using one window air conditioner when it is above 90 degrees and fans when it is above 80. This would cost $54.43 in Massachusetts 2010. There were 20 days above 90. This is the equation for those 20 days using a window unit:
0.9  x 14 x 1 x 12.8 x 20 = $32.25
And this is the cost of the fans used the other 55 days:
0.075 x 14 x  3 x 12.8 x 55 = $22.18
Total:
32.25 + 22.18 =$54.43
Much less than normal, but you still get air conditioning when it is really hot.



    In conclusion, air conditioning is great for the hot summer months, but they can drive up your electricity bill. Fans are a much cheaper alternative. Instead of always running the AC, you should only use it when it is really needed, and even then just one or two window units. You can save hundreds just by taking this advice.


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