If you use Amazon EC2 extensively, then you’ve fallen prey to the dilemma of “to reserve or not to reserve”. It is however a simple question in the sense that for a reserved instance, you pay a lesser per hour fee but end up paying an additional one-time fee up front. So what is the optimal break-even point where you know you are not spending more than required. EC2 pricing pagegives a high level number for break even point of Linux Reserved Instances.
The following table illustrates the percentage utilization needed for the break even point.
Having gone through this hair-pulling situation and from our experience of using EC2 for a while, PromptCloud has built an interactive EC2 price calculator that will help you better understand the AWS schemes that suit you best. You simply drag the “number of days/months” and “number of hours” sliders and it displays exact numbers on pricing. What better can you ask for an approximate use case :).