Main Differences b/t EC2 Saving Plans (Compute and Instance) and Reserved Instances

Question

Hi re:Post,
Thank you for your time and help!

Is below an accurate summary of some of the differences between 1) EC2 Savings Plans (Compute and Instance) and 2) EC2 Reserved Instances?

EC2

1)Savings Plans

A) Compute Savings Plans - flexibility.  Reduce bill by making a commitment to compute usage, ie for a commitment to a consistent amount of usage (measured in $/hour) for a 1- or 3-year term regardless of instance family, size, Availability Zone, Region, OS, or tenancy

B) EC2 Instance Savings Plans - lowest prices.  Reduce bill by making a commitment to instance family and region regardless of instance size, OS, and tenancy.

2) Reserved Instances - least flexible. Reduce bill by making a commitment to instance family, region, size, OS, and tenancy.

Thank you!
Best Regards,
Donald

re:Post Agent · Accepted Answer

Your summary of the differences between EC2 Savings Plans and Reserved Instances is generally accurate, but let me provide a more comprehensive comparison:

1. EC2 Savings Plans:

A) Compute Savings Plans:
- Offer the most flexibility
- Provide savings up to 66% off On-Demand pricing
- Require a commitment to a consistent amount of compute usage ($/hour) for 1 or 3 years
- Apply across EC2 instance families, sizes, AZs, Regions, OS, and tenancy
- Also apply to Fargate and Lambda usage

B) EC2 Instance Savings Plans:
- Offer savings up to 72% off On-Demand pricing
- Require commitment to a specific EC2 instance family in a chosen Region
- Provide flexibility in instance size, OS, and tenancy within the chosen family and Region

2. Reserved Instances (RIs):
- Offer up to 72% discount compared to On-Demand pricing
- Require commitment to a specific instance configuration (family, size, Region, OS, and tenancy)
- Come in two types: Standard (less flexible, higher discount) and Convertible (more flexible, lower discount)
- Provide capacity reservation in a specific Availability Zone (if specified)

Key differences:
1. Flexibility: Compute Savings Plans are the most flexible, followed by EC2 Instance Savings Plans, then Convertible RIs, and finally Standard RIs.
2. Scope: Compute Savings Plans can apply to EC2, Fargate, and Lambda, while RIs and EC2 Instance Savings Plans only apply to EC2.
3. Commitment: Savings Plans require a commitment to a consistent usage amount ($/hour), while RIs require commitment to specific instance attributes.
4. Capacity Reservation: Only RIs offer the option for capacity reservation in a specific Availability Zone.

It's worth noting that AWS now recommends Savings Plans over Reserved Instances for most use cases due to their greater flexibility and ease of use.  
**Sources**  
[Compute Savings Plans and Reserved Instances - Savings Plans](https://docs.aws.amazon.com/savingsplans/latest/userguide/sp-ris.html)  
[Reserved Instances for Amazon EC2 overview - Amazon Elastic Compute Cloud](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-reserved-instances.html)  
[Reserved Instances - Amazon EC2 Reserved Instances - AWS](https://aws.amazon.com/ec2/pricing/reserved-instances/)

Anil_AWS · Answer

It's all depending on your use case and how you plan to achieve your goals. As these Savings options provide you the discounts, it's up to how you utilize them based on your infra/workload setup and goals that you have. For example, if you have limited workloads that are very business critical with less changes on the setup in coming year either 1 year or 3 year and you have a goal to optimize cost, then you choose maximum savings option which gives bigger discount based on your commitment.

If you have a workloads which is managed by multiple business units scattered across regions and have plans to optimize or modernize in coming months then choosing SP's over RI would give better flexibility. At the end of the day, it's all up to your use case and your goals.

Remember Compute Savings plan not only covers EC2, but also covers Fargate & Lambda.

Main Differences b/t EC2 Saving Plans (Compute and Instance) and Reserved Instances

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