Time's Truth About Air Conditioners
Here's a great video from Time.com on how to save with your air conditioner.
As mentioned in the video, 20 BTUs per square foot is a general rule of thumb for how much A/C you might need, but as I've mentioned before, these rules don't apply to everyone. There are a number of factors that go into sizing an air conditioner properly. In fact I recommend not buying a new air conditioner without first consulting with a NATE-certified HVAC contractor to ensure the right air conditioner size for your home and lifestyle.