This tool allows you to estimate the absolute dollar figures of cost savings you can achieve in your AWS account by converting your AutoScaling Groups to Spot instances.

You can select various scenarios, such as to keep some of your instances as OnDemand in each group (maybe covered by Reserved Instances or Savings Plans), or only convert some of your AutoScaling Groups to Spot as part of a gradual rollout.

You may use any mechanism to adopt Spot, such as converting the configuration yourself group by group as per what you defined in the simulation.