Choose a Savings Plan when your priority is flexibility in how eligible compute usage changes; choose a Reserved Instance (RI) when your usage matches a defined instance configuration—or when you need capacity reserved in a particular Availability Zone. Savings Plans commit to a dollar amount of eligible usage per hour. EC2 RIs commit to instance attributes. Neither is automatically the cheapest choice: the outcome depends on your workload, eligible usage, capacity needs, and ability to use the commitment throughout its term.
What you commit to is the key difference
Savings Plans commit to hourly spend
A Savings Plan commits you to a consistent amount of eligible usage, measured in dollars per hour, for a one- or three-year term. The commitment applies to eligible usage according to the plan type and scope. If eligible usage falls below the committed amount, you can pay for commitment you do not use.
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AWS lists four Savings Plans types: Compute, EC2 Instance, Database, and SageMaker AI. The relevant comparison for EC2 compute is usually between Compute and EC2 Instance Savings Plans; Database and SageMaker plans are separate categories.
EC2 RIs commit to instance attributes
An EC2 RI applies a billing discount to eligible running On-Demand instances that match its terms. It is not, by itself, a physical server reservation. AWS describes RIs as a billing discount applied to running On-Demand Instances in your account.
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RI charges apply for the entire selected term whether or not you use the matching capacity. AWS offers All Upfront, Partial Upfront, and No Upfront payment options for RIs. Consider the cash-flow choice separately from whether the commitment matches demand.
How Savings Plans differ in flexibility
Compute Savings Plans
Compute Savings Plans can apply across EC2 instance families, sizes, Regions, operating systems, and tenancy. They can also apply to eligible Fargate and Lambda usage. This makes them a candidate when workloads may move between instance families or Regions, or between eligible compute services.
AWS advertises discounts of up to 66% off On-Demand rates for Compute Savings Plans. That is a vendor-stated maximum, not a typical result or a forecast for your account.
EC2 Instance Savings Plans
EC2 Instance Savings Plans apply to a specified instance family in a specified Region, while allowing changes in size, operating system, and tenancy within that scope. They are less flexible than Compute Savings Plans across families and Regions, but can fit usage that is stable within one family and Region.
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AWS advertises discounts of up to 72% off On-Demand rates for EC2 Instance Savings Plans. As with the Compute figure, treat this as a ceiling rather than an expected saving or a like-for-like comparison of your options.
After purchase, you cannot change a Savings Plan’s commitment terms. If eligible usage grows, you can purchase an additional plan; that does not increase or revise the existing commitment.
How Reserved Instance scope affects discounts and capacity
Regional RIs
A Regional RI applies within a Region and provides Availability Zone flexibility; it does not reserve capacity. Eligible Regional RIs may also provide instance-size flexibility, subject to platform, tenancy, and instance-family rules.
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Zonal RIs
A Zonal RI applies to a specified Availability Zone and reserves capacity there. Its matching scope is narrower than a Regional RI’s. AWS says Regional and Zonal RIs cost the same, so the choice is about scope, flexibility, and capacity reservation—not a different RI price.
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RI size flexibility is not universal. AWS lists exceptions that include specified GPU or accelerator families, Windows and certain commercial Linux platforms, and Dedicated tenancy. Check AWS’s current applicability rules for the exact instance, platform, and tenancy before counting on size flexibility.
An RI is not the only way to reserve capacity
If a workload needs capacity in a particular Availability Zone, compare a Zonal RI with a separate Capacity Reservation. A Regional RI offers no capacity reservation. Keep the billing discount decision distinct from the operational requirement to have capacity available in a specific zone.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Which option fits your workload?
| Workload or requirement | Options to evaluate first | Why |
|---|---|---|
| Usage may move between EC2 families or Regions, or between eligible EC2, Fargate, and Lambda usage | Compute Savings Plan | Its eligible coverage spans those services and EC2 dimensions. |
| Usage is stable within one EC2 family and Region, but may change size, operating system, or tenancy | EC2 Instance Savings Plan; eligible Regional RI | Both can accommodate some changes within a narrower family-and-Region scope. Verify RI eligibility for the specific platform and tenancy. |
| Capacity must be reserved in a particular Availability Zone | Zonal RI or separate Capacity Reservation | A Zonal RI reserves capacity in its selected zone; a Regional RI does not. |
| Demand is seasonal, migration-related, scheduled, or otherwise uncertain | Compare against On-Demand usage before committing | A commitment that outlasts or exceeds eligible demand can leave paid value unused. |
This is a starting point, not a universal price ranking. The best fit depends on the actual hourly usage that can receive each discount and on whether the operational flexibility or capacity benefit is valuable to you.
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Standard and Convertible RIs
Standard RIs cannot be exchanged. Convertible RIs can be exchanged during their term for another Convertible RI with different attributes. Both RI classes may allow modification of some attributes, but modification is not the same as exchanging one RI for another; check the current AWS rules for the attribute you need to change.
Sharing across accounts
Whether RI discounts or Savings Plans benefits are shared across accounts depends on your AWS Organizations billing settings. Do not assume a commitment purchased in one account will automatically benefit another. Review the organization’s discount-sharing configuration and the effect of any proposed changes on bills.
Quick Recap
Use account data to decide how much to commit
- Review historical hourly usage. Separate durable baseline demand from seasonal, scheduled, migration-related, or otherwise uncertain usage. A commitment sized to a temporary peak can be difficult to use after that peak passes.
- Identify valuable flexibility. If your compute may move across EC2 families, Regions, or eligible services, include Compute Savings Plans in the comparison. If demand is steady within one family and Region, also evaluate EC2 Instance Savings Plans and RIs.
- Resolve capacity needs. If the workload must run in a particular Availability Zone, evaluate a Zonal RI or a separate Capacity Reservation rather than treating a Regional RI discount as a capacity guarantee.
- Verify eligibility and ownership. Check RI size-flexibility eligibility for the precise instance, operating system, and tenancy. Establish which account owns the commitment and how organization-level sharing is configured.
- Estimate coverage and utilization. Use AWS recommendations and Purchase Analyzer to estimate cost, coverage, and utilization effects; use Cost Explorer to analyze savings against On-Demand. These tools help assess the account’s usage but do not make a headline maximum discount a prediction.
- Monitor after purchase. Track coverage and utilization as demand changes. If usage grows, assess a separate additional commitment rather than assuming the terms of an existing Savings Plan can be revised.
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