EC2 On-Demand vs Reserved Instance Cost Savings Calculator

The recent EC2 pricing change presents a compelling case for switching to reserved instances instead of on-demand instances. Provided you have the capital available to manage the upfront cost (and the confidence in your ability to pay for at least 1 year), the cost savings of switching to reserved instances are substantial. Hopefully this tool will help some of you save time when making the comparison.

This is a great tool. I use a spreadsheet to do something similar, but I like your implementation better. Thanks!

What would be cool is another column containing the number of months after which it makes no economic sense to stay with on-demand pricing, even if you never use the instance after that point. In other words, "if you're going to use this instance for at least 4 more months, you might as well get a reserved instance".