Can multiple EC2 Savings Plans be applied to the same instance?

Ideally, you should purchase savings plan when the requirements are freezed to have a streamlined commitment. But to answer the question, yes you can stack savings plan to benefit on the differential cost. You have to take into consideration that the new savings plan will have a different end date, therefore, you have to always be vigilant on the expiration cycle. https://aws.amazon.com/savingsplans/faq/ [Here you can get the answer if multiple savings plan can be stacked]

Hi there!

If you know you will use the instance without changing its family or region for at least one more year you can buy an additional EC2 savings plan. Note that it is difficult to calculate getting 100% coverage so be careful when buying additional savings plans because it you commit in excess you would be stuck paying for a commitment your instance can't meet. Purchase small and monitor the coverage. You can always get more savings plans if you'd want to commit more as there is no limit to how many savings plans you can purchase.

If for your workload you are using also Lambda and/or Fargate, I'd recommend considering Compute Savings Plans instead of EC2 Savings Plans, since those also cover for Lambda and Fargate.

I hope this helps.