After Amazon’s reserved instance pricing announcement last year, there were quite a few folks writing about the breakeven point for your ec2 instance i.e. the length of time you’d need to run your instance continuously before the reserved pricing turned out to be cheaper than the standard pay-as-you-go scheme. Looking around, I believe the general consensus was that it would take around 4643 hours or 6.3 months. See here,  here and here, for example.

Around late October of last year, Amazon announced even cheaper pricing for their ec2 instances. However, not seeing any newer breakeven numbers computed in the wake of lower prices, I decided to post some of my own. These are for one year reserved pricing for Amazon’s US-N-Virginia data center. All data is culled from the AWS ec2 page.

As we can see, the break even numbers have dropped quite a bit – down to 4136 hours on most of the instance types, a drop of almost 500 hours or so. That translates to better pricing 3 weeks earlier than before, in about 5.7 months. Interestingly enough, the high memory instances have slightly earlier break even points (by about 50 hours or so). Not quite sure why.