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Savings Plans commit you to a dollar amount of eligible usage per hour; EC2 Reserved Instances (RIs) commit you to instance attributes. A Compute Savings Plan can suit workloads that may move across EC2 families, Regions, or services. An EC2 Instance Savings Plan or RI can be worth evaluating when usage is stable within a family and Region. If you need capacity in a particular Availability Zone (AZ), consider a zonal RI or a separate Capacity Reservation: a Regional RI does not reserve capacity.
What are you committing to?
The difference in commitment basis is the starting point for a Savings Plans vs Reserved Instances decision. Savings Plans are commitments to a consistent amount of eligible usage, measured in dollars per hour, for a one- or three-year term. EC2 RIs are billing discounts tied to a consistent instance configuration for one or three years.
An RI is not a physical server reservation by default. AWS describes it as a billing discount applied to running On-Demand instances. Whether it also provides capacity depends on the RI scope: Regional or zonal.
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How do the options differ?
| Option | Commitment and eligible use | Flexibility | Capacity |
|---|---|---|---|
| Compute Savings Plan | Consistent eligible usage amount in dollars per hour; applies to eligible EC2 usage, Fargate, and Lambda. | Across EC2 families, sizes, Regions, operating systems, and tenancy. | Does not reserve EC2 capacity. |
| EC2 Instance Savings Plan | Consistent eligible usage amount in dollars per hour for a specified EC2 instance family and Region. | Allows changes in size, operating system, and tenancy within its family and Region scope. | Does not reserve EC2 capacity. |
| Regional RI | Instance configuration commitment for EC2 use in a Region. | Provides Availability Zone flexibility. Eligible configurations may also have instance-size flexibility. | Does not reserve capacity. |
| Zonal RI | Instance configuration commitment for EC2 use in a specified Availability Zone. | Narrower matching scope than a Regional RI. | Reserves capacity in the specified Availability Zone. |
AWS lists four Savings Plans categories: Compute, Database, EC2 Instance, and SageMaker AI. This comparison concerns Compute and EC2 Instance Savings Plans alongside EC2 RIs; Database and SageMaker AI plans are separate categories.
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Which kind of flexibility matters to your workload?
Choose broad service or Region flexibility when the workload may move
A Compute Savings Plan covers eligible EC2 use across instance families and Regions, as well as eligible Fargate and Lambda use. That wider scope can matter more than a narrower plan’s advertised maximum discount when your compute mix may change.
Consider a family-and-Region commitment for stable EC2 use
An EC2 Instance Savings Plan is narrower than a Compute Savings Plan: it is tied to a specified EC2 family and Region, while permitting changes in size, operating system, and tenancy within that scope. If your usage is steady in one family and Region, compare it with applicable RIs using your account’s estimates.
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Do not assume every RI can flex across sizes
Instance-size flexibility applies only to eligible Regional RIs. AWS’s applicability rules include exceptions for specified GPU or accelerator families, Windows and certain commercial Linux platforms, and dedicated tenancy. Check AWS’s current RI size-flexibility applicability list for your actual instance and platform before counting on size changes.
When is capacity reservation the deciding factor?
If the workload must be launchable in a particular AZ, a zonal RI is the RI option that reserves capacity there. A Regional RI provides AZ flexibility but no capacity reservation. AWS says Regional and zonal RIs cost the same; their distinction is scope, flexibility, and capacity reservation.
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If you need a capacity reservation but do not want the matching restrictions of a zonal RI, compare a separate Capacity Reservation with the billing commitment you choose. Keep the two needs distinct: a discount commitment does not itself guarantee capacity unless it is a zonal RI.
What happens if your usage changes or falls short?
Savings Plans commitments are fixed after purchase
A Savings Plans commitment term cannot be changed after purchase. If your eligible usage grows, you can buy an additional plan, but that does not increase or amend the existing commitment.
RI exchange and modification rules depend on RI class
Standard RIs cannot be exchanged. Convertible RIs can be exchanged during their term for another Convertible RI with changed attributes. Both RI classes may permit modification of some attributes; that is not the same as being able to exchange a Standard RI.
Unused commitments can still cost money
AWS says RI charges apply for the entire selected term regardless of use. RI payment choices include upfront, partial upfront, and monthly. With either type of commitment, buying more than your eligible usage can support can leave paid value unused. Evaluate the downside against the possibility that demand falls, shifts service, or changes configuration.
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Which option fits which situation?
| Workload situation | Options to evaluate | Reason |
|---|---|---|
| Usage may move between EC2 families or Regions, or between EC2, Fargate, and Lambda. | Compute Savings Plan | Its eligible-use scope spans those services and EC2 families and Regions. |
| EC2 use is stable within one family and Region, but size, operating system, or tenancy could change. | EC2 Instance Savings Plan; eligible Regional RIs | Both may accommodate some changes within defined scope; verify RI eligibility for size flexibility. |
| EC2 configuration and usage are predictable, with no requirement to reserve capacity in a particular AZ. | EC2 Instance Savings Plan or a Regional RI | Compare account-specific cost and utilization estimates; a Regional RI offers AZ flexibility without reserving capacity. |
| Capacity must be reserved in a specified AZ. | Zonal RI or a separate Capacity Reservation | A zonal RI reserves capacity in its AZ; a Regional RI does not. |
| Demand is uncertain or likely to shrink. | Assess commitment exposure before purchasing | An unused commitment may leave paid value without corresponding eligible usage. |
How should you size a commitment?
- Review historical hourly usage. Separate durable baseline demand from scheduled, seasonal, migration-related, or otherwise uncertain usage. AWS recommends using historical usage and its analysis tools; treating stable baseline demand as the first candidate for a commitment is a practical application of that guidance, not a guarantee of savings.
- Decide how much scope flexibility has operational value. If usage may move across EC2 families, Regions, or eligible services, compare a Compute Savings Plan first. If usage is steady within a family and Region, also evaluate an EC2 Instance Savings Plan and applicable RIs.
- Check for an AZ capacity requirement. If one exists, compare a zonal RI or a separate Capacity Reservation. A Regional RI does not reserve capacity.
- Verify technical eligibility. Before relying on RI size flexibility, confirm that the Regional RI, instance family, platform, and tenancy qualify under AWS’s current rules.
- Model payment, utilization, and ownership. Consider the effect of unused commitment, who in the organization owns it, and whether discounts are shared with the accounts using the eligible resources.
- Use AWS’s account-specific tools and revisit the result. AWS recommends reviewing usage and offers Purchase Analyzer to estimate cost, coverage, and utilization impact; Cost Explorer can help analyze savings against On-Demand. Check coverage and utilization after purchase rather than treating a headline maximum discount as a forecast.
How do billing and organization sharing affect the choice?
RI and Savings Plans discount sharing across accounts depends on AWS Organizations billing settings. Do not assume a commitment automatically benefits every account in an organization. Check the applicable sharing preferences and how a change would affect bills before deciding which account should hold a commitment.
How should you read AWS discount claims?
AWS’s Savings Plans types documentation advertises maximum discounts of up to 66% off On-Demand rates for Compute Savings Plans and up to 72% for EC2 Instance Savings Plans. These are AWS-published ceilings, not a measured 2026 customer result, an expected saving for an individual account, or a direct guarantee that one option will beat an RI. Actual value depends on eligible usage, commitment utilization, and current account pricing.
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